Solution: N900 Charging from dumb power sources *UPDATED*

[jabawok]

I have been wondering for 2 days since I received my N900 why charging seems hit and miss from non-PC based USB ports, for example car cigarette lighter USB adapters and USB Battery packs. Here's the answer and solution.

The Micro USB spec says that power draw should be under 100mA until the phone and connected power source device (ie laptop, computer, etc) can negotiate a higher current. This negotiation happens over the data pins (the center ones in the big USB plug). If the power source is a "dumb" device which is not capable of negotiation (for example the dedicated wall socket charger), the spec says that the data pins (D+, D-) should be shorted - indicating to the phone that it can draw as much power as it needs (up to 1A?)

My problem is that several USB Power sources that I have (a few car cigarette lighter to USB adaptors, and an APC Portable battery), have the center pins open. The phone therefore tries to negotiate with the dumb power source and obviously fails, and hence proceeds to ignore it.

There are a couple of solutions. For cigarette lighter to USB adaptors, you can probably just pull them apart and solder the 2 center pins of the USB socket together on the PCB. Another solution would be to cut your USB to micro USB cable in the middle, short the D+ and D- (usually white and blue wires from memory - check with a multimeter first!) and neatly join/heatshrink the cut. This would render the cable useless for anything except charging from the dumb power source.

In my case I neither wanted to sacrifice a USB cable, nor did I want to short the pins on the USB socket of my portable battery, as I wanted to retain its "passthrough mode", which transparently passes data through from a PC. Shorting the D+ and D- pins would destroy the passthrough mode.

Instead I salvaged a male to female USB part from an old USB hard disk enclosure (the cable that used to provide extra power to the USB hard disk). I cut the power cable off it, and heatshrinked the wires so they won't short. I then carefully soldered the center two conductors together in the USB socket.

Voila - a "Force Dedicated Charging" USB adaptor, for dumb USB power sources.

Attached are photos. (incidentally, taken with the n900 camera in macro mode - stunning. I had to downscale them for the forum, but the originals are here (http://www.jabawok.net/uploads/20091224-n900-charge-hack) if anyone is interested)

I wouldn't recommend you plug this adaptor into a PC - although it probably would do no harm as the ports are meant to be current limited, but shorting the data pins together will obviously terminate any communication on the USB bus.

UPDATE:
A lot of people have pointed out that the FM transmitter output power is reduced when plugging any sort of charger in (rendering the FM transmitter close to useless). Nokia have implemented this power reduction due to the fact that the charge cable will act as a transmit antenna, which brings the possibility that the transmit power will be well over legal limits.
If you would like to over-ride this power limitation at your own risk, with the possibility that you'll be transmitting at radio power levels over the legal limit, then grab the modified fmtxd binary from here:
http://jacekowski.org/Maemo/FMTXD
or here (zipped, post 8):
http://talk.maemo.org/showthread.php?t=60567

Make sure FM transmitter is off, then copy the new fmtxd to your n900 (root of the mass storage), then run the following in terminal:

cp /usr/sbin/fmtxd /home/user/MyDocs/fmtxd.original.backup
sudo gainroot
cp /home/user/MyDocs/fmtxd /usr/sbin/
exit


You should now be able to charge as well as simultaneously transmit (possibly illegally) on FM.

UPDATE 2:
Added photo of my current solution (last photo in below series). These weren't hard to find on ebay, (usb male to female adaptor) and the same solder bridge trick was applied. Much neater than original hack.

[Laughing Man]

Is it possible to buy a cable that has the pins shorted? How would they be idenitified?

[jabawok]

Definitely won't be possible to buy a cable with the pins shorted.

Let me be clear that this cable/adapter is USELESS for transferring data, or for charging from a PC USB port.

The sole purpose of this hack is to force the phone to think that it's plugged into a dedicated charger (which I call a dumb power source).

You only need to think about doing something like this if you have a USB socket which the phone will not charge from (and you want it to).

For everybody else, I recommend you buy dedicated wall chargers and dedicated car chargers - these will already have the D+ and D- pins internally shorted, and never need to transfer data.

[fnordianslip]

Cool. I just opened up my USB charger lighter adapter, and bridged the two inner data terminals as you suggest, and now my N900 will charge from it. Unfortunately, the FM transmitter becomes very weak when connected.

This aspect of the N900 is very lame indeed - it works fine when not charging, but why on earth would I want to flatten the device's battery when I'm listening to it through the car stereo?

[jabawok]

I haven't had a chance to experiment with the FM transmitter yet, but I would assume this is a hardware limitation, possibly to do with grounding or something that occurs which reduces the efficiency of the radio transmitter. It's early days: it'll be interesting to see what hacks people come up with to solve this problem.
UPDATE: told ya! see solution in opening post.

[go1dfish]

When I tried using the FM transmitter while plugged into a laptop, the n900 flat out told me that the FM Transmitter couldn't be active while USB is connected.

[TA-t3]

The FM transmitter's most obvious use case would be as an in-car music system, so it's indeed very strange that it won't work right when also connected to a car charger.

[fnordianslip]

When I tried using the FM transmitter while plugged into a laptop, the n900 flat out told me that the FM Transmitter couldn't be active while USB is connected.
Sorry for going off topic here.

I've never seen that happen, and I've experimented a fair bit. I can always hear the FM TX on my handheld FM receiver when it is activated. I get about 3 metres range with no USB cable attached and a good fully-quieting signal (no hiss), depending on device and antenna orientation.

When I plug the wall charger, or my newly functional car charger in to the N900, the signal level drops drastically, such that when the N900 and FM radio are right next to each other, the radio still hisses and pops, although I can hear the transmitted signal.

[Svengalis]

Is it possible to buy a cable that has the pins shorted? How would they be idenitified?

Yes, these cables exist but they are usually built as 2-into-1, so you can pool the available amperage from two USB ports to power a single device.

[That One Guy]

You just saved me 30 bucks!

I have one of those 12V Cigarette adapters that has 2 USB ports on it. I could never get to work with my N900.

So, I popped it open, heated up my handy dandy soldering iron, jumped the two center pins on each USB port on the circuit board, re-assembled it, and Vioala! The N900 charges!

Thanks again! :D

[sjgadsby]

I haven't had a chance to experiment with the FM transmitter yet, but I would assume this is a hardware limitation...

No, it's bug 6792 (https://bugs.maemo.org/show_bug.cgi?id=6792), fixed internally and slated for inclusion in some future firmware update.

[fnordianslip]

No, it's bug 6792 (https://bugs.maemo.org/show_bug.cgi?id=6792), fixed internally and slated for inclusion in some future firmware update.

Are you sure this is the same thing? The FM transmitter does work, with the USB charger attached, it just works very, very badly. I get no error message at all.

[lancewex]

Pictures for the curious would be most appreciated! (If possible)

L

You just saved me 30 bucks!

I have one of those 12V Cigarette adapters that has 2 USB ports on it. I could never get to work with my N900.

So, I popped it open, heated up my handy dandy soldering iron, jumped the two center pins on each USB port on the circuit board, re-assembled it, and Vioala! The N900 charges!

Thanks again! :D

[jackburton]

Wow, you made my day with this post. I went ahead and soldered the two data leads of a flex USB adapter I have and it works like a champ. I'm not good with a soldering iron. It's an ugly joint but it works. I have confirmed that this now works with an iPhone USB wall adapter and the Belkin USB/3 AC outlet adapter. The flex adapter was easy to modify because it is held together by two screws and is not molded together. I got this awhile back at www.cyberguys.com but they don't seem to have this anymore.

Here are some pictures:
http://www.flickr.com/photos/brandersnaxe/4210350827/

http://www.flickr.com/photos/brandersnaxe/4211116724/

http://www.flickr.com/photos/brandersnaxe/4210352687/

http://www.flickr.com/photos/brandersnaxe/4211120280/

http://www.flickr.com/photos/brandersnaxe/4211122794/

[cheeze[it]]

wow, I hope I don't have an issues with my power block. I just ordered this:Zagg Sparq (http://www.zagg.com/accessories/zaggsparq.php) I was planning to use it to charge multiple device and also hoped it would charge the N900 on the go. So I guess I'll just cross my fingers and hope for the best =(

[texaslabrat]

;440411']wow, I hope I don't have an issues with my power block. I just ordered this:Zagg Sparq (http://www.zagg.com/accessories/zaggsparq.php) I was planning to use it to charge multiple device and also hoped it would charge the N900 on the go. So I guess I'll just cross my fingers and hope for the best =(

I have a Zagg Sparq and it does not charge my N900 with a normal USB cable. I have ordered the "official" nokia adapter (which changes old-school nokia charger output into mini-usb, presumably with the data pins shorted), as well as a couple of extra usb cables which I intend to hack along the lines illustrated in this post.

[guy2die4]

can a software patch fix it instead of a hardware modification?

[Laughing Man]

I need to buy a Nokia adapter somewhere (besides eBay since I don't want to bother with eBay unless it's the last option). NokiaUSA doesn't seem to sell them.

[That One Guy]

Pictures for the curious would be most appreciated! (If possible)

L

Short middle pins.

[jackburton]

For anybody who doesn't want to hack anything together, I have found another solution. Get a Motorola SKN6252 mini-usb to micro-usb adapter. Then use a regular A to mini-b USB cable from the dumb charger. I have verified this to work. I got the adapter from Amazon http://www.amazon.com/Micro-Adapter-SKN6252-Alltel-Motorola/dp/B000IBLD3E. I am using this 'shorty' cable from Cyberguys.com: http://www.cyberguys.com/product-details/?productid=10030.

Here is an action shot:
http://www.flickr.com/photos/brandersnaxe/4227462726/

[twoboxen]

For anybody who doesn't want to hack anything together, I have found another solution.

Are you sure that it isn't just luck of the draw? Meaning, maybe the amperage is within tolerance to work. I had one dumb usb charger work and another that never did.

Seems like grounding those pins might be the only full solution.

[jackburton]

I do not think this Motorola adapter is luck of the draw. Even the instruction diagram indicates its use for using a car charger with mini-usb for use with a micro-usb phone. Here is the usage sheet:
http://www.flickr.com/photos/brandersnaxe/4227505038/

[Laughing Man]

For anybody who doesn't want to hack anything together, I have found another solution. Get a Motorola SKN6252 mini-usb to micro-usb adapter. Then use a regular A to mini-b USB cable from the dumb charger. I have verified this to work. I got the adapter from Amazon http://www.amazon.com/Micro-Adapter-SKN6252-Alltel-Motorola/dp/B000IBLD3E. I am using this 'shorty' cable from Cyberguys.com: http://www.cyberguys.com/product-details/?productid=10030.

Here is an action shot:
http://www.flickr.com/photos/brandersnaxe/4227462726/

Wait so you have to get both? Since the Amazon one only goes from Micro to Mini USB.

[jackburton]

You need the motorola adapter and a decent mini-usb cable. I got the adapter for 99 cents on Amazon. I just tried it with an old PSP USB cable I have. Had to plug and unplug a few times, but it is charging now.

[twoboxen]

I do not think this Motorola adapter is luck of the draw. Even the instruction diagram indicates its use for using a car charger with mini-usb for use with a micro-usb phone. Here is the usage sheet:
http://www.flickr.com/photos/brandersnaxe/4227505038/

Interesting... though, i'm wondering if the motorola phones it's replacing would have the same issue with other "dumb" micro usb chargers.

Does that make sense?

[optimaxxx]

what would happen if i just ripped out the two pins?

[jackburton]

Okay here is a gotcha with this adapter. Make sure the adapter is plugged into the N900 FIRST.

THEN plug in the DC mini-usb cable. I couldn't get charging to start otherwise..

[Le_Petit_Lapin]

Last time i tried soldering something I burnt a hold clean through a graphics card. I think its probably best if I give this a miss.

[jackburton]

One more gotcha. Apply power only when the N900 is on the home screen, otherwise charging may not start. Don't ask me why. It seems to start every time when on the home screen.

[ossipena]

what would happen if i just ripped out the two pins?

nothing compared to unmodified ports. the pins must be shorted, theyre insulated by default and ripping those out would still keep the pins insulated.

[tokuro]

For anybody who doesn't want to hack anything together, I have found another solution. Get a Motorola SKN6252 mini-usb to micro-usb adapter. Then use a regular A to mini-b USB cable from the dumb charger. I have verified this to work. I got the adapter from Amazon http://www.amazon.com/Micro-Adapter-SKN6252-Alltel-Motorola/dp/B000IBLD3E. I am using this 'shorty' cable from Cyberguys.com: http://www.cyberguys.com/product-details/?productid=10030.

Here is an action shot:
http://www.flickr.com/photos/brandersnaxe/4227462726/

I have SKN6252 and it does not make my dumb mini USB chargers work with n900. I have about 8+ of those and only 1 works with N900 using SKN6252.

[twoboxen]

I have SKN6252 and it does not make my dumb mini USB chargers work with n900. I have about 8+ of those and only 1 works with N900 using SKN6252.

Thanks for this. This is exactly what I suspected. Shorting the pins is the only for-sure answer.

[mikec]

Just shorted the center pins on my cheapie cig lighter usb adaptor and it now works like a charm. Charging using the supplied n900 usb cable. Many thanks for this.

Mike C

[guy2die4]

is there a way to short the centre pins without a solder iron?

[mikec]

is there a way to short the centre pins without a solder iron?

Not safely. You have got +5v and ground on either side. Shorting these may not be good.

[tennis_player]

I've found this cable that seems to be just what we need to charge our n900. I purchased it based on the "bad" reviews which in our case is exactly what we need. So charge only, no sync.

http://www.bestbuy.com/site/Rocketfish%26%23153%3B+Mobile+-+USB+Charging+Cable/8705181.p?id=1199496059678&skuId=8705181&st=RocketFish%20RF-CA1MRA&cp=1&lp=1

I have a zagsparqq that only worked occasionally with the provided cable, with this cable it worked right away. You can find it on ebay for much cheaper. Hope this helps.

[woodyear99]

I have a ac adapter with a usb port on it. I was just wondering if it is safe to use with the supplied usb cable as a second charger.

It says output dc 5v max: 1000ma min: 150 ma

Would this be safe to use with my n900?

Hmm I plugged it in, it workd, but do you think this could damage my n900 in any way?

[TA-t3]

It depends on the quality of the charger. It's difficult to tell without checking it out with instruments. But if you can get your hands on a multimeter and measure its voltage it could give an indication. If it provides between 5V and 5.2V or so, and not something wildly different, then it may be OK. No guarantees though. Many China-made chargers are total rubbish, while others are completely fine. If it was provided as part of a kit with some decent, well-known product, then it's probably OK as well.

[woodyear99]

Nah actually it was a cheap chinese kit I ordered off ebay for my sansa mp3 player. I just may skip using it with my n900, not taking any chances on this one lol. Will try to purchase another usb cable instead.

[jeffsf]

;440411']wow, I hope I don't have an issues with my power block. I just ordered this:Zagg Sparq (http://www.zagg.com/accessories/zaggsparq.php) I was planning to use it to charge multiple device and also hoped it would charge the N900 on the go. So I guess I'll just cross my fingers and hope for the best =(

It does NOT charge the N900 -- on 20-40 min hold with Zagg to see how they intend to resolve.

[cheeze[it]]

It does NOT charge the N900 -- on 20-40 min hold with Zagg to see how they intend to resolve.

try different cables... I will be doing so. I ordered the nokia adapters, the other adapters mentioned and will consider that rockfish cable as well. Somethigns gotta work ^_^

[jeffsf]

Zagg is now aware of the issue (apparently they did not have any "official" reports prior to this morning) and of this thread. They were very responsive to the call.

To be clear, the ZAGGSparq looks like a great product, nearly as nice as the now-discontinued APC UBP10 (http://www.apcc.com/resource/include/techspec_index.cfm?base_sku=UPB10-EC). I'm hoping that they can provide a self-contained N900 solution.

I'm not much up for carrying a ton of special cables. I've had it with a charger for everything. That was the whole point of USB charging!

[TheLongshot]

Zagg is now aware of the issue (apparently they did not have any "official" reports prior to this morning) and of this thread. They were very responsive to the call.

I had sent them an E-Mail last week on the subject, but I hadn't had time to respond to their response.

[twoboxen]

I'm not much up for carrying a ton of special cables. I've had it with a charger for everything. That was the whole point of USB charging!

exactly. that's what is so frustrating about nokia's engineering decisions here. are they just trying to make a few extra bucks off specialty chargers like everyone else (standardization be damned)?

[God's Toy]

Hey just so you know, Jawbone chargers work fine in the N900! (using the USB post that is!)

(Note: The mA output of the Nokia is rated at 1200mA/h were the Jawbone is 550mA/h. It will take longer to charge the N900 using it but if it's an over night charge it will be fine)

[tennis_player]

It does NOT charge the N900 -- on 20-40 min hold with Zagg to see how they intend to resolve.

the zaggsparq does charge the n900, it just doesn't do it with the cable provided by Nokia. You need a charging usb cable and not a data and charge cable.

Best Buy sales them, so give it a try.

http://www.bestbuy.com/site/Rocketfish%26%23153%3B+Mobile+-+USB+Charging+Cable/8705181.p?id=1199496059678&skuId=8705181&st=RocketFish%20RF-CA1MRA&cp=1&lp=1

[jeffsf]

You need a charging usb cable and not a data and charge cable.

Thank you, but I only want to carry one USB cable. Period.

Zagg has been very responsive. They actually called me back today, New Year's Eve, within a couple hours of my first inquiry, to let me know that they had located a N900 and tested it with the ZAGGSparq and confirmed that the N900 appeared ill-behaved. They also found that the "Power saving mode" seemed to have some impact on if it would charge properly or not.

I am coming to the conclusion that this is basically a fault of the N900 -- I should be able to plug its supplied USB cable, or any "real" USB cable, into any reasonable USB power device out there (which the iPhoneiPod have kindly populated in cars and airports everywhere) and have the N900 charge.

That the N900 had problems even recognizing the supplied AC-10 suggests to me that they need to fix this in firmware. If Nokia can't, in my opinion, this is a significant enough problem to warrant a recall/replace program.

[jeffsf]

http://www.bestbuy.com/site/Rocketfish%26%23153%3B+Mobile+-+USB+Charging+Cable/8705181.p?id=1199496059678&skuId=8705181&st=RocketFish%20RF-CA1MRA&cp=1&lp=1

$15 for a charging cable?? You gotta be f-in kidding.

You can buy a Nokia OEM AC or DC charger for less than that through reputable channels. Amazon sells the car cords for around $15 and the wall chargers are half that or less.

[TheLongshot]

$15 for a charging cable?? You gotta be f-in kidding.

Sure. That's why I bought one off of E-Bay for about 6 bucks shipped. In the near term I'm going to need my Zagg Sparq to charge up my N900. Until the problem gets worked, that seems to be the best solution to the problem. And yes, I think the solution is probably going to have to come from Nokia.

[cheeze[it]]

Do you think a firmware update can solve the issue or is it a hardware thing...

[jeffsf]

It is likely firmware somewhere, but not clear if it is flashable firmware.

There is most likely a charging circuit in the device, either discrete or perhaps part of the USB chipset, that handles the negotiation of draw from the USB leads. Since the N900 will charge without being booted up, the logic of charging can't be completely handled by Maemo. However, it is possible that the configuration of the charging circuit can be done through the appropriate bus from Maemo to change the behavior of the charging circuit to one that is more reliable.

Edit -- Apparently there has been at least one bug related to failed detection of USB and lack of charging addressed in
https://bugs.maemo.org/show_bug.cgi?id=6004
This has been fixed in package
kernel 2.6.28-20094603+0m5
which is part of the internal build version
2009.46-16

This appears prior to the rumored candidate firmware "PR-11" based on week 51 builds.

[Rushmore]

It is likely firmware somewhere, but not clear if it is flashable firmware.

There is most likely a charging circuit in the device, either discrete or perhaps part of the USB chipset, that handles the negotiation of draw from the USB leads. Since the N900 will charge without being booted up, the logic of charging can't be completely handled by Maemo. However, it is possible that the configuration of the charging circuit can be done through the appropriate bus from Maemo to change the behavior of the charging circuit to one that is more reliable.

Edit -- Apparently there has been at least one bug related to failed detection of USB and lack of charging addressed in
https://bugs.maemo.org/show_bug.cgi?id=6004
This has been fixed in package
kernel 2.6.28-20094603+0m5
which is part of the internal build version
2009.46-16

This appears prior to the rumored candidate firmware "PR-11" based on week 51 builds.

That was my point last month, that there is some form of handshake taking place and is likely by design to avoid some of the more "cheap" charges from frying the device. Very unlikely this could happen, though the design is more complex than simply allowing all dumb chargers based on correct current draw to work. This is why I suggest it was designed this way on purpose.

[woodyear99]

It is likely firmware somewhere, but not clear if it is flashable firmware.

There is most likely a charging circuit in the device, either discrete or perhaps part of the USB chipset, that handles the negotiation of draw from the USB leads. Since the N900 will charge without being booted up, the logic of charging can't be completely handled by Maemo. However, it is possible that the configuration of the charging circuit can be done through the appropriate bus from Maemo to change the behavior of the charging circuit to one that is more reliable.

Edit -- Apparently there has been at least one bug related to failed detection of USB and lack of charging addressed in
https://bugs.maemo.org/show_bug.cgi?id=6004
This has been fixed in package
kernel 2.6.28-20094603+0m5
which is part of the internal build version
2009.46-16

This appears prior to the rumored candidate firmware "PR-11" based on week 51 builds.

That particular bug is annoying it happens all the time once my phone is locked, have to unlock and then plug in the phone each time I charge via usb.....

[jeffsf]

That was my point last month, that there is some form of handshake taking place and is likely by design to avoid some of the more "cheap" charges from frying the device. Very unlikely this could happen, though the design is more complex than simply allowing all dumb chargers based on correct current draw to work. This is why I suggest it was designed this way on purpose.

As an EE, I find that hard to swallow.

As long as, within reason, the proper voltage is being supplied to the USB port, then it is up to the charging circuit to determine how much current it will draw. If you hook a 5V supply to a 25 ohm load, you'll consume 1 Watt from any supply can source 200 mA or more.

There is some complexity with internal resistance of the supply, but that is a secondary effect which, if anything, a "smart" charger could be aware of, dropping its current demands when the supply voltage starts to droop, hence automatically accommodating everything from the poorly-regulated CLA from the guy with the port-a-table on the corner, through my 350 mA Plantronics charger, to a Nokia OEM charger can can source 1200 mA.

That the N900 allows "shorted data" USB supplies to bypass the handshake contraindicates the hypothesis that this is somehow supposed to "protect the charger."

I find it reasonable that Nokia is worried about the case where

I hooked my N900 to my laptop and it fried my $3000 laptop.

but find it unreasonable that they are worried enough to "lock out" virtually all non-active-USB-hub devices (including problems with their own DC and AC adapters) for the case where

I hooked my N900 to my no-name CLA and it fried the CLA.

which generally would be prevented by any well-designed "smart charger" circuit (which would be looking at the charging current and voltage both),
or even

I hooked my N900 to my no name CLA and it cooked my N900.

"Well, what did you expect?" would be the polite form of the comments someone would likely get in the latter two cases. In neither case, if the charger had the data pins shorted, would the apparent N900 behavior, have saved the charger or the N900.

[TA-t3]

As another EE I can only agree.. the charger must supply the proper voltage, and it should be clean. If those are OK there's no way the charger could fry the N900.

[Rushmore]

As an EE, I find that hard to swallow.

As long as, within reason, the proper voltage is being supplied to the USB port, then it is up to the charging circuit to determine how much current it will draw. If you hook a 5V supply to a 25 ohm load, you'll consume 1 Watt from any supply can source 200 mA or more.

There is some complexity with internal resistance of the supply, but that is a secondary effect which, if anything, a "smart" charger could be aware of, dropping its current demands when the supply voltage starts to droop, hence automatically accommodating everything from the poorly-regulated CLA from the guy with the port-a-table on the corner, through my 350 mA Plantronics charger, to a Nokia OEM charger can can source 1200 mA.

That the N900 allows "shorted data" USB supplies to bypass the handshake contraindicates the hypothesis that this is somehow supposed to "protect the charger."

I find it reasonable that Nokia is worried about the case where

I hooked my N900 to my laptop and it fried my $3000 laptop.

but find it unreasonable that they are worried enough to "lock out" virtually all non-active-USB-hub devices (including problems with their own DC and AC adapters) for the case where

I hooked my N900 to my no-name CLA and it fried the CLA.

or even

I hooked my N900 to my no name CLA and it cooked my N900.

"Well, what did you expect?" would be the polite form of the comments someone would likely get in the latter two cases.

My undergrad is in computer electronics, so appreciate your points, but I am trying to give Nokia the benefit of the doubt for a seemingly odd design decision;)

[jeffsf]

I am trying to give Nokia the benefit of the doubt for a seemingly odd design decision;)

We're certainly dealing with a few "interesting" implementation artifacts, and I expected that when I bought a 1st-generation device.

Maybe it is that if you can't charge the device, you don't see the rest of them? ;)

[denix]

We're certainly dealing with a few "interesting" implementation artifacts, and I expected that when I bought a 1st-generation device.


Isn't it a 4-th generation device? ;)

What a shame - all my backup batteries are useless now! And they always worked with the rest of my equipment - dumb/smart phones, headsets etc... :(

[shadowjk]

As an EE, I find that hard to swallow.

As long as, within reason, the proper voltage is being supplied to the USB port, then it is up to the charging circuit to determine how much current it will draw. If you hook a 5V supply to a 25 ohm load, you'll consume 1 Watt from any supply can source 200 mA or more.


The USB standard allows devices to draw 100mA. A full 500mA can be provided if the device negotiates this with the connected host. The host's usb ports should be overcurrent protected and shut down the power if the device consumes too much power.

This is why you can't just use the logical method of draw power until voltage drops.

A new charging profile was added to the usb standard, which includes signaling for letting the device know when it can behave as if it was connected to a charger. For cheap/dumb chargers, the simple signaling of d+ and d- shorted together is used.

The N900 complies with the USB charging standard, but the problems come from everyone using random nonstandardized charging schemes before the USB charging standard was finalized.

It's worth noting that there's no usb charging over miniusb, for example..
[/quote]

That the N900 allows "shorted data" USB supplies to bypass the handshake contraindicates the hypothesis that this is somehow supposed to "protect the charger."


The usb charging supplement is available to the public. Might contain some clues to the design decisions made


I find it reasonable that Nokia is worried about the case where

I hooked my N900 to my laptop and it fried my $3000 laptop.


iirc there already was a case where someone hooked it up to a freerunner and nearly fried it. A prototype n900 I think. Sadly, in practice it seems many computers lack effective overcurrent protection on USB and will happily shove 20 amps over it until something fries and voltage drops from 5 to 0 in one go :)


In neither case, if the charger had the data pins shorted, would the apparent N900 behavior, have saved the charger or the N900.

I think the datapins shorted together decision might have been to make the most unambigous way of distinguishing between a computer's usb power and a charger, some computers give power on usb when off/suspended, but have nothing on the datapins.

To me it looks like they (the usb standards body) picked the most reliable and inexpensiv way of distinguishing between a real usb host and a charger.

[woodyear99]

Saw this selling cheap on amazon, think this would work with the N900?


http://www.amazon.com/Music-Power-0900-72-Rechargeable-Extended/dp/B000QFNK6K/ref=sr_1_4?ie=UTF8&s=automotive&qid=1262622611&sr=8-4

[Bratag]

http://talk.maemo.org/showthread.php?t=36922&page=5

This page about half way down there is a guide for modding a standard USB cable to fool the N900 into charging from it. Pretty basic stuff if you have a soldering iron and a pair of wire cutters. Essentially the same as the OP but in cable form. You can buy like 10 min to micro adapter cables for 3 bucks from amazon and mod them keeping one everywhere you go, USB to micro USB cables are everywhere nowdays so I chose that as my option.

[choubbi]

Just as a sidenote, the charger for HTC HD2 works with the N900.

[eladts]

Another off the shelve solution that does not involve soldering is the iGo USB Charging Cable (http://www.igo.com/Accessories/USB-Charging-Cable/invt/ps002710003) coupled with the A97 (http://www.igo.com/A-Series-Tips-for-Mobile-Devices/iGo-power-tip-A97-for-select-mobile-devices/invt/660069701) power tip. Works with every USB source that I tried. It looks like it does the shortening of the data pins only on the tip side, so you can even use it to charge from a PC without messing its USB bus.

[Master of Gizmo]

I charger), the spec says that the data pins (D+, D-) should be shorted - indicating to the phone that it can draw as much power as it needs (up to 1A?)


As i've already written in another thread: The spec does not say to shorten them. Instead the spec says that you are supposed to connect them via 200 ohms. The n900 may work fine when shortening them, but shortening something always means that some significant power may flow over this short circuit. Using 200ohms instead is safe for any hardware as the current over the resistor is limited to 3.3V/200Ohms = 17mA.

These resistors cost nothing and may protect that hardware, so they are really a good investment.

[whealy]

I had some USB adapters for car power points (http://catalog.belkin.com/IWCatProductPage.process?Product_Id=489423) that I could not get to work with USB cables. So I picked up a cable to modify as suggested in this thread. Before I did that I needed to get something off the phone. But when I tried to use the cable as a data connection, it didn't work, it just charged. But based on the comments here about after doing the mod it would only be useful for a charge, I decided to retry these cables on my belkin plugs. For whatever reason, they worked without modification. I can only assume that they are manufactured this way. Anyway, the cables I used can be found here (http://www.bestbuy.com/site/Rocketfish%26%23153%3B+Mobile+-+USB+Charging+Cable/8705181.p?id=1199496059678&skuId=8705181&st=rocketfish usb&cp=1&lp=3)

[Laughing Man]

Another off the shelve solution that does not involve soldering is the iGo USB Charging Cable (http://www.igo.com/Accessories/USB-Charging-Cable/invt/ps002710003) coupled with the A97 (http://www.igo.com/A-Series-Tips-for-Mobile-Devices/iGo-power-tip-A97-for-select-mobile-devices/invt/660069701) power tip. Works with every USB source that I tried. It looks like it does the shortening of the data pins only on the tip side, so you can even use it to charge from a PC without messing its USB bus.

Have you tested this? If so can you try using just the A97 tip and any USB to microUSB cable?

[LinuxPrfsnl]

I have the Seidio Micro/USB charging cable (for Palm Pre) which works with no mods.
Comes with the data connectors looped.

http://www.seidioonline.com/product-p/cbuptr800.htm

[denix]

I am a big fan of retractable cables and my existing USB-to-microUSB sync cable didn't work. So I have found I perfect solution for me - dual-head sync+charge retractable cable (black head for sync/charge, red is modified for charge only):

http://www.seidioonline.com/product-p/cbuymcr2.htm

Just verified it works with N900, although they say only works with Palms, Blackberries and Droids - I guess it just follows the spec...

May not be the cheapest solution, but universal - my BT headset does not require microUSB cable mods, so I now can charge N900 and BT from a battery backup using the single cable!

http://www.cyberguys.com/images/detail_images/p35678a-1.jpg

[devbike]

Found this while cruising the ThinkGeek clearance sale:

http://www.thinkgeek.com/clearance/b43f/

That could be a solution for those (like myself) that already have a kit of portable USB batteries and universal (pre-standard) charging cables. < $10 is a nice price point, too :)

[jellotherat]

Found this while cruising the ThinkGeek clearance sale:

http://www.thinkgeek.com/clearance/b43f/

That could be a solution for those (like myself) that already have a kit of portable USB batteries and universal (pre-standard) charging cables. < $10 is a nice price point, too :)

I looked at that too, but when I emailed the manufacturer (Boxwave) to find out if it was a standard extension cable with the data pins shorted I got some crazy answer that it has "a special circuit within the adapter" that "alters the signals coming out of the charger". Since there are no "signals" coming out of the charger, I suspect he had no idea what he was talking about. Has anybody tried this and can verify that it works?

[splandorf]

Hi,

Have you verified that both the charging tip and the data tip work correctly w/ the N900?

(I saw some posts on Blackberry forums that people could get their devices charged w/ this cable, but that the data connection tip wasn't connecting to their PC/laptop.)

Thanks!

Sam


I am a big fan of retractable cables and my existing USB-to-microUSB sync cable didn't work. So I have found I perfect solution for me - dual-head sync+charge retractable cable (black head for sync/charge, red is modified for charge only):

http://www.seidioonline.com/product-p/cbuymcr2.htm

Just verified it works with N900, although they say only works with Palms, Blackberries and Droids - I guess it just follows the spec...

May not be the cheapest solution, but universal - my BT headset does not require microUSB cable mods, so I now can charge N900 and BT from a battery backup using the single cable!

http://www.cyberguys.com/images/detail_images/p35678a-1.jpg

[twoboxen]

Have you verified that both the charging tip and the data tip work correctly w/ the N900?

FYI I didn't want to pay that much for a cable not knowing if it would even work especially, so I spliced my own. The longer cable has its data pins grounded while the shorter one can be used to sync with a pc. Both types of connections work great. I have a nice solar charger (http://www.powerfilmsolar.com/products/portable_remote/index.php?cat=pr_usb), and it now works charging the n900!

each adapter totaled about $5, though I'm sure you can probably dig around more and find some of the parts cheaper. I did get the added joy from being able to make my own :)

[denix]

Hi,

Have you verified that both the charging tip and the data tip work correctly w/ the N900?

(I saw some posts on Blackberry forums that people could get their devices charged w/ this cable, but that the data connection tip wasn't connecting to their PC/laptop.)

Thanks!

Sam

Hmm, it's strange that I missed your question earlier...

Yes, as I said earlier - I tested the cable and both tips seem to work as advertised with my N900 - the red one only charges and the black one charges and syncs, but only when connected to a PC. I tested it with Mass storage mode by transferring some files.

[tangigi]

Hello,

I Have a usb car charger and when I tested it with a voltage meter, it gives a reading of 5.6. Is this acceptable or too high?

cheers

larry

[robertwbrandt]

I'm glad I found this thread. I was doing all kinds of testing, killing myself, trying to figure this out this problem

But I found since the latest software upgrade, I don't need an extra cable or do any weird modifications. While testing with various different USB power supplies and different cables, I found that nearly every time, All I needed to do was connect the USB cable (which would do nothing), unplug the USB cable and then plug it back in. The second time I plug in the USB cable the device detects the power supply and works....

It would still be better if the device would work on the first instance of plugging in the cable, but it is a relatively small inconvenience.

Thanks
Bob

[splandorf]

DENIX: thanks for getting back!

And Robertwbrandt: I will try this trick (I have PR 1.1 now) -- but if no-go then I will order the split cable Denix posted about.

Thanks,
Sam



I'm glad I found this thread. I was doing all kinds of testing, killing myself, trying to figure this out this problem

But I found since the latest software upgrade, I don't need an extra cable or do any weird modifications. While testing with various different USB power supplies and different cables, I found that nearly every time, All I needed to do was connect the USB cable (which would do nothing), unplug the USB cable and then plug it back in. The second time I plug in the USB cable the device detects the power supply and works....

It would still be better if the device would work on the first instance of plugging in the cable, but it is a relatively small inconvenience.

Thanks
Bob

[vinz486]

Ok, my Cellular Line (very good brand) car charger do not work with N900.

Worked fine with N97.

After reading this thread i've opened the microusb connector and... surpise! There is a resistor between the ground and one of data pin (i suppose D+).



So... where is the standard?

Dumb USB chargers must have a resistor between D+ and D- or only D+ must be put to the ground?

This charger works with ALL microusb devices EXCEPT N900...
I think that this is an implementation BUG of N900 that must be solved to permit users to use 43,874 usb chargers on the market...

[robertwbrandt]

I agree that it is a N900 bug. My own experience both with charging USB devices and the N900 seems to indicate this.

Here's hoping the next software version fixes it. Question: Does anyone have any experience with the other Nokia Maemo tables and USB charging?

[TooMuchMoney]

Does anyone know if the Nokia CA-101 cables are already shorted in this way?

I have connected this directly to many desktops / laptops. I have connected to car charges with USB female sockets (originally for iPods/iPhones). I have connected to wall charges with USB female sockets (again for iPods/iPhones) and all seems to be working fine.

Perhaps this is the simple solution? Buying Nokia original cables... I got them of eBay for about £1.50 delivered.

[klinglerware]

I am a big fan of retractable cables and my existing USB-to-microUSB sync cable didn't work. So I have found I perfect solution for me - dual-head sync+charge retractable cable (black head for sync/charge, red is modified for charge only):

http://www.seidioonline.com/product-p/cbuymcr2.htm

Just verified it works with N900, although they say only works with Palms, Blackberries and Droids - I guess it just follows the spec...

May not be the cheapest solution, but universal - my BT headset does not require microUSB cable mods, so I now can charge N900 and BT from a battery backup using the single cable!

http://www.cyberguys.com/images/detail_images/p35678a-1.jpg

I use the Boxwave MiniSync for the N97. Same principle - retractable cable that has both a sync/charge and a charge only connector.

I agree that it is pricier than the home-brew solution, but it is convenient.

http://www.boxwave.com/products/minisync/minisync-retractable-cable-nokia-n97_3550.htm

[shadowjk]

The CA-101 cables are not shorted that way. They are datacables. If the D+ and D- were shorted together, or if D+, or D- were shorted to ground in any way, then communication would not work.

CA-101 will charge the phone when connected to a computer that is alive, and the computer agrees to supply power to the phone.

D+ to ground is not the correct way to identify as a charger. D+ and D- should be connected together.

You can find the Battery Charging spec at usb.org (http://www.usb.org/developers/devclass_docs), in a zip (http://www.usb.org/developers/devclass_docs/batt_charging_1_1.zip). batt_charging_1_1_FINAL.pdf

Page 7 shows the connection, “A Dedicated Charging Port is required to short the D+ and D- lines with a resistance of RDCHG_DAT”, page 29 specifies max 200 ohms across D+ and D-. Although the wording on page 7 suggests it should be exactly 200 ohms... Also on Page 29, a minimum of 2 MEGA ohms of resistance between D+ and ground or vbus. That is, not connected together at all.

[digitalat0m]

Well.. i took the plunge for the N900 knowing about this going in thinkin, hey it won't be so bad.. but after 3 days of ownership i forgot my charger in a hotel room.. talk about ANNOYING! all my USB wall plugs and car chargers cannot charge this stupid brick :( I had a nice infrastructure of USB chargers to keep my gadgets alive, the most important gadget the N900 is the only one that won't charge :(

[tso]

browsing brando, this showed up:
http://mobile.brando.com/brando-workshop-usb-to-micro-usb-cable_p04980c0704d003.html

it appears that they have removed the data pins (observer the close up of the usb a side).

[slewis1972]

just noticed 2 entries on ebay that charge from usb:

http://shop.ebay.co.uk/?_from=R40&_trksid=p4522.m38.l1313&_nkw=n900+usb+charge&_sacat=See-All-Categories

retractable one would be handy.

Scott

[TooMuchMoney]

I just recently bought another iPod/iPhone mains plus car charger and works perfectly with original CA-101 cable.

Just a heads up.

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=150402013104&ssPageName=STRK:MEWNX:IT

Maybe it's coincidence but both chargers designed for iPods/iPhones seems to work.

[geneven]

Kindle chargers work and are combo electrical outlet/usb chargers.

[crenquis]

Is it possible to buy a cable that has the pins shorted? How would they be idenitified?

I have some Gomadic "tips" that are charge-only.
This one looks like a charge-only micro-usb tip:
TIP-0000-69 (http://www.gomadic.com/tip-69.html)

Gomadic cables definitely aren't cheap, but they are handy when you have many different devices (most of mine are mini-usb, but my wife has many different manufacturers).

I use my charge-only mini-usb tips with one of the motorola mini-micro adapters to charge my n900 with battery packs/outlets/etc.

[blue13x]

ZAGGsparq Recalled, Owners Get A Free Replacement: http://thenokiaguide.com/2010/02/16/zaggsparq-recalled-current-owners-get-a-free-replacement/

There seems to be a problem with the current Sparq, and a new 2.0 version should be on the way in Late March.

[denix]

ZAGGsparq Recalled, Owners Get A Free Replacement: http://thenokiaguide.com/2010/02/16/zaggsparq-recalled-current-owners-get-a-free-replacement/

There seems to be a problem with the current Sparq, and a new 2.0 version should be on the way in Late March.

There may be a recall for early ZAGGsparqs, but definitely not because it cannot charge N900! :) With the proper cable, suited for dumb chargers (as this lengthy thread discusses) my ZAGGsparq charges my N900 just fine...

[crenquis]

Gizmodo.com just posted a piece about a cable that has a switch that shorts the data lines. So you can have one cable for charging and data transfer.
It is available here:
sync-blocker cable (http://usbfever.com/index_eproduct_view.php?products_id=1746)

[mcdull]

I bought this and it works for my N900 with USB AC Adatpers that couldn't charge when I used other regular data cables.
Less than $4 for 2.

http://cgi.ebay.com/2-Retractable-USB-Charger-For-Nokia-8600-Luna-N86-N900_W0QQitemZ170442750331QQcmdZViewItemQQptZUK_Mo bilePhones_MobilePhoneAccessories_MobilePhoneCharg ers?hash=item27af2df97b

[laurencemaemo]

I had the same problem what I did was use a regular nokia car charger with the supplied N900 power adapter.
works a treat.

[alfmar]

I hacked a spare USB cable and finally saw my N900 battery charging from an external battery. Yay!

http://www.freeimagehosting.net/uploads/47a46fd5cc.jpg

That black Li Ion external battery is a BixPower BAT PM-55 (http://www.bixpower.com/ProductDetails.asp?ProductCode=Bat-PM55&CartID=1).

My PM-55 has lots of charge/discharge cycles, thus I cannot give "performance" figures.

[zimon]

I browsed through all these 10 pages rather quickly, so sorry if this is already answered;
Could this however correct way (USB standard (http://talk.maemo.org/showpost.php?p=496596&postcount=81)) of demand to shortcircuit D+ and D- be overridden somehow in software, through dbus or kernel parameter perhaps?

It would just be so convenient to click something from a menu, than always carry both either self made or bought adapter (http://www.thinkgeek.com/clearance/b43f/) and normal USB-data cable (http://www.dealextreme.com/details.dx/sku.26313%7Er.74602803).
So both synchronizations, fast data transfers and charge anywhere could be achieved.

[flydeep]

I would be very wary about using anything retractable. The cable could retract and pull the usb port with it ...

I browsed through all these 10 pages rather quickly, so sorry if this is already answered;
Could this however correct way (USB standard (http://talk.maemo.org/showpost.php?p=496596&postcount=81)) of demand to shortcircuit D+ and D- be overridden somehow in software, through dbus or kernel parameter perhaps?

It would just be so convenient to click something from a menu, than always carry both either self made or bought adapter (http://www.thinkgeek.com/clearance/b43f/) and normal USB-data cable (http://www.dealextreme.com/details.dx/sku.26313%7Er.74602803).
So both synchronizations, fast data transfers and charge anywhere could be achieved.

[zimon]

I would be very wary about using anything retractable. The cable could retract and pull the usb port with it ...

I have two of those, very handy. The forces are rather weak, won't break anything although the locking mechanism would open in the middle.

...just tried. It won't even have force to pull from the computer's USBA connector if I unlock the "yo-yo" when it is connected.

[volt]

Has anyone tried the cable crenquis mentioned (http://talk.maemo.org/showpost.php?p=536041&postcount=90) usbfever Sync Blocker (http://usbfever.com/index_eproduct_view.php?products_id=1746) yet? I assume it blocks sync by shorting, but if it blocks by disconnecting the data wires, it wouldn't work for charging...?

Brando has a similar adapter (http://mobile.brando.com/mini-usb-to-micro-usb-adapter-w-on-off-switch_p04979c0704d003.html), smaller and cheaper. The description says it has an on/off switch but the images clearly show that it has a toggle switch for sync/charge. I am guessing this has the same functionality as the usbfever one.

Both devices claim compatibility with the N900, but that can be for sync only for all I know. Either of these might work, but has anyone tested? I think I might order one to try.

[geohsia]

Brando has a similar adapter (http://mobile.brando.com/mini-usb-to-micro-usb-adapter-w-on-off-switch_p04979c0704d003.html), smaller and cheaper. The description says it has an on/off switch but the images clearly show that it has a toggle switch for sync/charge. I am guessing this has the same functionality as the usbfever one.

Thanks for the link. Have you tried it? The Brando version looks like a better option. Who needs a 50" cable?

The only concern about this adapter is the size might put unnecessary strain on the connector. The N900 seems to have a weak connector so this may be an issue.

[raholco]

Way back when in the early days of the WinMo smartphone cable hacking was done to get the HTC Typhoon (SPV C500/Audiovox SMT5600) to charge required shorting one of the data pins to ground.

When I saw this post and recalling the Nokia N900's behavior brought this memory back to me.

AS a side note-for those who don't want to solder you can get conductive ink pens to make bridges to create paths between any two points.

[SLDeviant]

Thanks for the link. Have you tried it? The Brando version looks like a better option. Who needs a 50" cable?

The only concern about this adapter is the size might put unnecessary strain on the connector. The N900 seems to have a weak connector so this may be an issue.

Bought it , doesn't work.... very annoyed but caveat emptor. :mad:

When its in sync mode, it will both sync and charge, when its in charge mode it doesn't do anything. I've tried every order and combination of plugging and unplugging and its still useless.

Second edit:

With a different mini-usb cable, the stock APC cable that came with the universal battery, it will charge. Mysteries abound as the APC cable will also datasync, but I'm not going to question the great techno-loa that have blessed me with a working pair of external batteries.

[geohsia]

With a different mini-usb cable, the stock APC cable that came with the universal battery, it will charge. Mysteries abound as the APC cable will also datasync, but I'm not going to question the great techno-loa that have blessed me with a working pair of external batteries.


I got it as well and as far as I can tell it works. I'll try all my USB / mini cables to see if there's one that doesn't. Hopefully they all work

[jimx]

I have been wondering for 2 days since I received my N900 why charging seems hit and miss from non-PC based USB ports, for example car cigarette lighter USB adapters and USB Battery packs. Here's the answer and solution.<snip>

Hope this info helps someone out!

You totally rock man, this post is spot on, huge thanks for takin the time n trouble. :D

[volt]

Thanks for the link. Have you tried it?

I ended up buying that one, yes, and it works.

Bought it , doesn't work.... very annoyed but caveat emptor. :mad:

When its in sync mode, it will both sync and charge, when its in charge mode it doesn't do anything. I've tried every order and combination of plugging and unplugging and its still useless.

Second edit:

With a different mini-usb cable, the stock APC cable that came with the universal battery, it will charge. Mysteries abound as the APC cable will also datasync, but I'm not going to question the great techno-loa that have blessed me with a working pair of external batteries.

I don't completely trust it to always work with all chargers, but so far it has seemed to be working the few times I've used it.

[Mike Fr]

browsing brando, this showed up:
http://mobile.brando.com/brando-workshop-usb-to-micro-usb-cable_p04980c0704d003.html

it appears that they have removed the data pins (observer the close up of the usb a side).

I bought this cable for $8 at Brando's and it charges the N900.
Thanks for this thread and all the ideas.

[Laughing Man]

Does anybody own a New Trent IMP880? Since the ZaggSparq is still sold out, I'm considering buying it. E-mailing New Trent they said it has a USB port but they can't guarantee it works with the N900 since they don't test Nokia devices (only iPhones and Blackberries).

Hoping to get it before Otakon since I'll probably spend alot of time watching videos or surfing on 3G while my sister runs about..

[eladts]

I bought this cable for $8 at Brando's and it charges the N900.
Thanks for this thread and all the ideas.

Brando also has a Mini USB to Micro USB adapter with on/off switch (http://shop.brando.com/mini-usb-to-micro-usb-adapter-w-on-off-switch_p04160c0006d001.html), which costs $6. It works the same way as their switchable Micro USB cable, letting you choose between dumb charger mode and PC connection mode. It may be useful to those who have lots of Mini USB cables and chargers.

[Laughing Man]

Does anybody own a New Trent IMP880? Since the ZaggSparq is still sold out, I'm considering buying it. E-mailing New Trent they said it has a USB port but they can't guarantee it works with the N900 since they don't test Nokia devices (only iPhones and Blackberries).

Hoping to get it before Otakon since I'll probably spend alot of time watching videos or surfing on 3G while my sister runs about..

Update to this post. It works but you can't use the USB cable that came with the N900. You have to use the charging tip they provide (or a charging USB cable with the data pins shorted).

[quipper8]

fwiw, a micro usb cable plus wall adapter from a palm treo pro works great

Actually, I think it charges the battery faster than the included ac adapter if that is possible

[jabawok]

Updated Opening post with some more potentially useful info. hopefully google will index it.

[munkiii]

Brando has a similar adapter (http://mobile.brando.com/mini-usb-to-micro-usb-adapter-w-on-off-switch_p04979c0704d003.html), smaller and cheaper. The description says it has an on/off switch but the images clearly show that it has a toggle switch for sync/charge. I am guessing this has the same functionality as the usbfever one.

I've got one of these, along with a USB to mini-USB cable.

Works great for anything with a usb port (except Sky+ boxes).

[Val Demar]

Just bought a XP8000 Energizer PowerPack from buy.com, it came with a so-called "iPad adapter" (product link (http://www.energizerpowerpacks.com/us/products/accessories.html), web-site contains a typo, the actual model is PC007). It was not in the original XP8000 box but included with the purchase. I can now charge my phone with this adapter from a dumb USB charger that wouldn't work before with a standard data cable. It's ridiculously pricey if bought separately ($10 - $20 + S&H), but if someone is considering a back up power pack then XP8000 + PC007 for $49.99 seems like a reasonable deal (link (http://www.buy.com/prod/energizer-8000mah-universal-battery-pack-w-ipad-tip/q/loc/111/216795526.html)), considering you can use this charging adapter with other sources.

[jessi3k3]

Just bought a XP8000 Energizer PowerPack from buy.com, it came with a so-called "iPad adapter" (product link (http://www.energizerpowerpacks.com/us/products/accessories.html), web-site contains a typo, the actual model is PC007). It was not in the original XP8000 box but included with the purchase. I can now charge my phone with this adapter from a dumb USB charger that wouldn't work before with a standard data cable. It's ridiculously pricey if bought separately ($10 - $20 + S&H), but if someone is considering a back up power pack then XP8000 + PC007 for $49.99 seems like a reasonable deal (link (http://www.buy.com/prod/energizer-8000mah-universal-battery-pack-w-ipad-tip/q/loc/111/216795526.html)), considering you can use this charging adapter with other sources.
woot.com had it for 39.99 a month or so ago. I nabbed it up right away and it's been working fine since. My only gripe is that the battery led meter is useless. You have 4 bars of energy 75% of the time. Then you have 3 bars 20% of the time. The last 5% is almost never seen, I've never seen it myself It usually goes from 4->3->0. I still get a good 4 full charges while in use (gps running, etc.) in before it dies.

[Val Demar]

Yeah, I'm looking forward to always having this baby in my back pack, otherwise I always keep thinking about battery discharge while on the go. 39.99 is a steal, prices like this make one wonder what are the profit margins for stores selling products at MSRP.

[Rebski]

In trying to source the Energizer PC007 (PC07?) without much joy.

Is this the sort of thing we are looking for
http://www.lindy.co.uk/ipad-usb-charging-adapter/73336.html?gclid=CNy5o4GxqKUCFZBO4Qod_ms1jg

[Val Demar]

In trying to source the Energizer PC007 (PC07?) without much joy.

Is this the sort of thing we are looking for
http://www.lindy.co.uk/ipad-usb-charging-adapter/73336.html?gclid=CNy5o4GxqKUCFZBO4Qod_ms1jg

Looks like you can get them (http://www.amazon.com/gp/offer-listing/B003WHER8E/ref=dp_olp_0?ie=UTF8&redirect=true&qid=1290016973&sr=8-1&condition=all) through Amazon, however at $20+ with S&H it is a rip-off IMO.

[johnherro]

Jabawok, I downloaded fmtxd1.3, renamed it to fmtxd, and did what you said. The frequency of the FM Transmitter widget changed to 76.00 MHz, and when I tried to change it in Settings, FM Transmitter, Frequency, it said "Unable to use FM Transmitter" when I clicked Save. When I restore the old fmtxd from the backup, I can change the frequency. Any ideas? Thanks!

[jalyst]

Think you might be in the wrong thread.
Good luck with it though :)

Jabawok, I downloaded fmtxd1.3, renamed it to fmtxd, and did what you said. The frequency of the FM Transmitter widget changed to 76.00 MHz, and when I tried to change it in Settings, FM Transmitter, Frequency, it said "Unable to use FM Transmitter" when I clicked Save. When I restore the old fmtxd from the backup, I can change the frequency. Any ideas? Thanks!

[telecomgeek79]

Hey just so you know, Jawbone chargers work fine in the N900! (using the USB post that is!)

(Note: The mA output of the Nokia is rated at 1200mA/h were the Jawbone is 550mA/h. It will take longer to charge the N900 using it but if it's an over night charge it will be fine)

The one I like to use is the Jawbone car charger. Just plug it in to the outlet, the regular N900 data cable to that and the N900, and away you go.

I did one of those, let's see if it works, things...and it did.

L8r

[jabawok]

Jabawok, I downloaded fmtxd1.3, renamed it to fmtxd, and did what you said. The frequency of the FM Transmitter widget changed to 76.00 MHz, and when I tried to change it in Settings, FM Transmitter, Frequency, it said "Unable to use FM Transmitter" when I clicked Save. When I restore the old fmtxd from the backup, I can change the frequency. Any ideas? Thanks!

Pretty sure those instructions were written in the PR1.2 days. might need to find a freshly cracked fmtxd methinks. Having said that, the fmtxd that comes with PR1.3 seems to not attenuate the power quite as much when charging, so it hasn't been a problem for me.

[biketool]

So if you go into H-E-N and the battery power metering logic is disabled is it possible to charge from a dumb cable?
I would like to use my 6V(AC) bicycle dynamo and dumb miniUSB phone charge rectifier-regulator5.2V(DC) to charge the N900 without too many weird adapters. Perhaps I will split the cable insulation in a mini-micro adapter and short the cables although I would prefer to leave things as they are for best weather resistance.
worst case I can use a miniUSB to nokia2mm and then my nokia 2mm 3mm adapter although that gets to be too much junk on the end of the cable.
Hacked or DIY power supplies and cables are how I burned out three of my four Zaurus PDA's back in the day so I am hesitant since I can't replace my N900.

[peppino]

Hi, I trying this (http://www.ladyada.net/make/mintyboost/index.html) project for load battery on the road.
5V is generated without problem, the signal D- and D+ has 1.9V, when I try to attach N900 to my step up the charge not start. In dmesg I see:

twl4030_usb twl4030_usb: HW_CONDITIONS 0x50/80; link 1
twl4030_usb twl4030_usb: HW_CONDITIONS 0xd0/208; link 2

I tried also with 0.7V on D- D+ as written in batt_charging_1_1_FINAL.pdf but nothing.
I have the kernel 2.6.28.10power46.
I would like start the charge with only 500mA and not 1000mA. With 200 Ohms between D- and D+ which is the maximum source current?

Thank you for the help

[Val Demar]

My guess is that N900 needs more than 500mA to charge, for example I regularly see my N900 fails to charge reliably from USB ports on desktop PCs.

[peppino]

Maybe the problem is desktop pc with windows. In my pc with Linux the charge work always good. I need about 4 hours for full charge.

I discovered somethings. With 200Ohms beetween D+ and D- the charge is 1000mA Wall Adapter.
In this post http://talk.maemo.org/showpost.php?p=658278&postcount=861 i read the settings of BME on the chip BQ24150. So I tried to stop BME and launch the script, the charge works well, but I don't have none graphical feedbacks.
Can I set the registers of BQ24150 while the BME is running?
Can I tell to BME with socket unix start the charge?

Thank you

EDIT:
In the script I changed the value of register 0x01 with 0x48 (500mA)

[shadowjk]

bme is not configurable.

Even if the charger can't get sufficient current it'll generally take what it can get, down to 300-400mA or so as long as the voltage is sufficiently stabilized.

[PMaff]

In trying to source the Energizer PC007 (PC07?) without much joy.

Is this the sort of thing we are looking for
http://www.lindy.co.uk/ipad-usb-charging-adapter/73336.html?gclid=CNy5o4GxqKUCFZBO4Qod_ms1jg

This may also help:
http://talk.maemo.org/showthread.php?t=75300

[joerg_rw]

As i've already written in another thread: The spec does not say to shorten them. Instead the spec says that you are supposed to connect them via 200 ohms. The n900 may work fine when shortening them, but shortening something always means that some significant power may flow over this short circuit. Using 200ohms instead is safe for any hardware as the current over the resistor is limited to 3.3V/200Ohms = 17mA.

These resistors cost nothing and may protect that hardware, so they are really a good investment.

Hi, I trying this (http://www.ladyada.net/make/mintyboost/index.html) project for load battery on the road.
5V is generated without problem, the signal D- and D+ has 1.9V, when I try to attach N900 to my step up the charge not start. In dmesg I see:

twl4030_usb twl4030_usb: HW_CONDITIONS 0x50/80; link 1
twl4030_usb twl4030_usb: HW_CONDITIONS 0xd0/208; link 2

I tried also with 0.7V on D- D+ as written in batt_charging_1_1_FINAL.pdf but nothing.
I have the kernel 2.6.28.10power46.
I would like start the charge with only 500mA and not 1000mA. With 200 Ohms between D- and D+ which is the maximum source current?

Thank you for the help


I browsed through all these 10 pages rather quickly, so sorry if this is already answered;
Could this however correct way (USB standard (http://talk.maemo.org/showpost.php?p=496596&postcount=81)) of demand to shortcircuit D+ and D- be overridden somehow in software, through dbus or kernel parameter perhaps?

It would just be so convenient to click something from a menu, than always carry both either self made or bought adapter (http://www.thinkgeek.com/clearance/b43f/) and normal USB-data cable (http://www.dealextreme.com/details.dx/sku.26313%7Er.74602803).
So both synchronizations, fast data transfers and charge anywhere could be achieved.


Since somebody referred to this thread today, I like to add some late clarifications:

The spec says "SHORT D+ and D-", the 200Ohm are MAXIMUM. For any EE that's a pretty unambiguous spec that defines a valid range of 0 .. 200 Ohm for the shorting - pin to pin, including all cable resistance, contact resistance and all, which is what the 200 Ohm are meant to specify: you must not exceed this value.
Bottom line: using resistor is BAD, short the pins by simple solder jumper.

The max current with shorted (by significantly less than MAX 200Ohm, best value:0) D-pins is basically undefined, N900 will try to draw up to ~900mA from any charger that signals "fastcharger" by the shorting method.

For charging in software, there's shadowJK's http://enivax.net/jk/n900/charge21.sh.txt script now, based on my original draft quoted some posts back.
Alternative source edited by me for 500mA charge: http://maemo.cloud-7.de/maemo5/patches_n_tools/charge21_500mA-USBlimit__UNTESTED.sh
Keep in mind you probably have to `stop bme`, otherwise the charging script and BME will conflict and not work correctly.

/j

[eleseur]

I tried the data pins short trick today, i've heard of it before but never had to use it until now.

I was trying to charge my n900 of a solar battery/charger controller with a usb out, and wasn't getting anything. I tore the usb module out snice it has nice leads attached to it on a pcb, and shorted the data pins with a quick joint.

Hooked it up to a sepic tuned for 5v running off 8x nimh aa's in two sets of four (6v, ~4ah), soldered the leads to the output on the sepic and it charged now.

So what exactly does this mean in terms of mah's being put into the battery with the pins shorted, or time it takes to charge? More/less than the stock 1000ma 5v input?

I assume even if i get the full 2a my sepic is rated for, it should be fine, as i've hooked my n900 alone up to a 2a usb hub and nothing bad happened. I doubt its like a led where it takes all the current it can get, and all that really matters is the voltage (up to a point, super high current could short circut your phone).

Anyway, female usb cables are dirt cheap, this works just fine with an aftermarket usb cable as well. Get a cheap sepic, a lipo pack, and a female usb port and you got a nice little usb backup battery thats not rediculously overpriced, diy, and easy to upgrade parts/batteries.

[shadowjk]

N900 insructs its charger chip to charge at max 950mA. How much that translates to in the input depends on battery voltage and the efficiency of the charging chip.

[bingomion]

@joerg_rw: Any chance we can have a fix integrated on power kernel?

[mariotomo]

https://www.facebook.com/photo.php?fbid=10151890217419497&set=pcb.10151890228794497

probably I should have tried the software solutions before demolishing the cable, but I had quite a few spare ones and I enjoy soldering. this one works fine.