blck | # 191 | 2012-09-05, 09:23 | Report

Hi,
after my USB-Port broke, I got really careful updating stuff, because I knew that I wouldn't be able to reflash. Well yesterday, nevertheless, it happened. Now my beloved and hopefully not late n900 is stuck to a boot loop.
Does anyone know a good repairshop in Germany, preferably in Berlin?

Estel, since you have a good insight into the hardware of the n900, what do you think of building a docking station. I'm planning on using the golden dots below the battery and the battery pins to build kind of a dock. I would build a wooden plattform drilling holes where I have to connect the dots (connecting them sing long metal poles) and find a way to connect the battery pins of the n900 to a external power source. With such a docking station one could use the n900 as a Rasberry Pi kind of server.
Unfortunately it sounds like a lot of work

Regards,
blck

Estel | # 192 | 2012-09-05, 12:52 | Report

Docking station is absolutely good idea, for device that doesn't have normal USB connection. Furthermore, You could add 5V 2A fuse to 5V line, and diode preventing reverse polarity (elements, that are lacking while using pads beneath battery) - without worrying about their size. (would be incorporated into docking station).

Of course, using station, You don't have much chance of situation, where fuse would save You - but, adding it, is negligible work, compared to rest of station building. Other than that, you're not missing any elements - sure, no external ESD protection for USB lines, but chip have internal ones, rated for 8,8kV. Should be sufficient, if You're not planning to catch lightning strikes with Your device

Despite of what some* claims, it should be no problem I know people, who are using pads under battery as everyday way of connecting USB (in environment without any anti-ESD "safety thingies"), for a year already, without single problems.

/Estel

*mentioned "some" should be knowledgeable enough, because "they" are e. engineers - although, with all due respect, real life > e. engineers experience, so I wouldn't be worried about it.

blck | # 193 | 2012-09-05, 16:00 | Report

Hi Estel,
thanks for your quick answer. As far as I can see out of this thread, I only have to make connections to the D+, D-, GND and 5V (with your 2A(mpere) fuse and Diode (what do you mean here?).
Which material for my "connecting pins" do you would recommend?
What kind of power connection you would recommend (e.g. cut an old Nokia Charger open and then use the appropriate cables)?

I thought of using a plastic box with a thick lid (putting the pins through here), do the wiring inside (beeing careful as hell that no cables will ever meet) and at the end putting some fancy small LEDs inside for the look

Cheers,
blck

Estel | # 194 | 2012-09-06, 11:24 | Report

Yea, that would suffice. Just be sure, to not use battery - (minus) as ground - it's marked wrong way in 1st post of thread You've linked. Shouldn't burn anything, and probably would work OK (battery - is connected to ground plane anyway), but it's still better to use ground from testpads, just like other things.

As for contact pins, I woudl recommend spring-like connectors - just like device is using for speakers, audio jack, etc (You will notice it upon disassembling N900). You can use very small, "normal" springs too - just be sure, that in any conditions, they won't bend and short some random testpads...

Also, remember, that You need *both* battery (either real, or fake, via something connected to battery pins, with 3rd battery pin connected to ground via 100k Ohm resistor), and 5V/Ground "fake charger", for establishing USB connection.

Easiest way, IMO, is to take upper part of battery (this one with pins - as a bonus, it contains BMI Pin shorted to ground via 100k resistor, already implemented), then put it on piece of wood or plastic cut in shape of battery cell. This way, You will have "fake" battery, containing pins for contact with testpads (of course You need to manufacture those pins Yourself, on Your fake battery).

/Estel

// Edit

Or search for "N900 JAF" cable - it should be exactly what You need, and cost around 10 USD max AFAIK, it's exactly "fake battery", with springs for testpads already in place. you would just need to tear it's cable (it's standard RJ45 plug, useless for Your case), and test with multimeter, which one corresponds with battery +, ground, 5V, USB DATA + and USB DATA -; then connect it to appropriate things (and isolate other cables).

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Last edited by Estel; 2012-09-06 at 11:30.

blck | # 195 | 2012-09-12, 10:04 | Report

Hi Estel,
well the JAF-Box looks like the way to go. I mean it looks like the Docking Station I was about to build. And if the RJ45-Adapter (the network-thing) supplies enough power and if the flasher recongnizes the n900 via network it should be possible to flash the n900, shouldn't it?
Even if not with the JAF-Box it looks like a easy task, cut off the RJ45, measure what is what, connect USB accordingly, flash my beloved n900, sell my new Android phone

Cheers,
blck

aeon_light | # 196 | 2012-09-12, 16:02 | Report

Hey everyone,

While the JAF box idea looks interesting (and quite convenient and relatively cheap - there's one going for about 35 USD on EBay right now), the JAF cables for the N900 that I've seen so far don't actually connect the USB pins - they seem to use the serial pins for flashing (similar to how other Nokia phones work), which apparently doesn't work for the N900.

Estel | # 197 | 2012-09-16, 14:01 | Report

In fact, I never meant using JAF box - I just though about it's "cable", as I suspected them to have correct pin layouts, already.

Hoever, it was just common sense/wild guess, and aeon_light (thanks a lot - as said earlier, I have never seen such N900 cable physically, just though that makers of those have brain, actually...) denied it. It's unbelievable, that they have screwed it to the point of trying to use serial connection on cable *dedicated* for N900 :/

aeon-light, question about cables You've seen - does they have, at least, full pin layout for N900 testpads (unconnected, so we can just swap cables, cut RJ45, and have it "fixed"), or they're just lacking rellevant spring-pins at all (USB+,USB-,5V, at least - ground is easy to mimic anyway).

/Estel

blck | # 198 | 2012-10-05, 15:43 | Report

Hi,
so alright I invested a few bucks in the idea. aeon_light is right, the jaf-cables do not connect to the data + and data - pins as shown in picture 1.
They can be used however as "fake battery" (box-picture attached) even if the wiring is a bit weird.
I cut off the RJ45-connector and labeled the cables accroding to picture one (box-cable-picture attached).
The wiring in an usb-cable is pretty clear. I labeled it as per defintion (see usb-cable picture).

Before I cut open my Nokia-Charger I wanted to discuss some things.
First problem, since the pins of the box do not connect to the data+ and data- pins from picture 1, but to the mbus-port I think I won't be able to flash (I may try though - n900 is a brick in the moment anyway.)
Second thing is, that the battery wiring in the box looks a bit weird. While the plus-pin has its own cable soldered on, the minus-pin and the gnd are connected with a resistor. Furthermore there is an additional resistor connected between the gnd-pin and its cable. Maybe someone can bring some reasoning in it?
As far as I can see it I would have to connect the minus-cable from the charger (I really do hope it is colorcoded aswell) to the minus-part of the box-cable, do the same for the plus-part and connect gnd and gnd?
Then I would connect the d+ (usb-cable) to the TX-Pin (box) and the d- (usb-cable) to the RX-Pin (box). At least if I go after this post. It would sure make more sense to connect it to the d+ and d- pins of the phone, but that's not possible (the box does not offer any connectors).

Picture 1:


Anyway I will stop at this point and see if smb got further ideas...

So far, blck

Attached Images

   

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Last edited by blck; 2012-10-05 at 15:49. Reason: Attached better pictures

Estel | # 199 | 2012-10-07, 22:35 | Report

Well, having it in hand - would it be hard to manually add 2 additional pins for USB data + and - ? Via drilling small hole and using small piece of metal, or heating metallic pin and pushing it through fake battery, then reinforcing in correct position?

As for battery connectors in fake-battery - isn't it just 100kOhm resistor between BMI pin and ground? The 2nd element - between ground pin and actual ground - isn't resistor for sure - it's either diode, or fuse, or something else, but not resistor (hard to tell from photo).

*Don't* try to flash via Rx pins instead of USB D+ and D-... It won't work, anyway, and IIRC components on Rx thingie are very fragile for out-of-spec voltage - even USB one could fry it easily. For being able to flash, You need to modify "fake battery" to contain pins for USB D+ and D-.

/Estel

/Estel

sEKI | # 200 | 2012-10-08, 08:55 | Report

It does look like a diode to me but shouldn't it be connected the other way round with the resistor? I though that BSI needs 100K resistor from GND and on the picture it looks like the resistor is connected to GND...
Your "minus-cable" and gnd will be the same. I'm not sure though can you feed 5V straight in from the charger. Remember that the battery is rated at 3.7V but you can see voltage ranges from 3.2V to 4.2V... Can anyone confirm if there's any sort of voltage regulator in the phone and it's safe to feed 5V straight to battery pins?