How to (really) brick a tablet - How to recover?
 

Well, unfortunately I found out a simple way to brick the N800. :o :(

This applies to all the Nokia tablets - if while in root you (stupidly) write to /dev/mtdblock0 (and likely mtdblock1-3, too!) you will overwrite the boot loader and brick the device.

It seems like I accidentally did this (I can't fully be certain that was the cause since the tablet won't boot) when attempting to mount a jffs2 image. I think I might have accidentally transposed /dev/mtdblock0 for /tmp/mtdblock0. ( It might be a good idea for someone to change the Maemo wiki so that someone else doesn't also stupidly do that. I would also recommend using a script if you're going to try a jffs loop on the tablet - and checking it to make ceratin it's correct about 5 times before executing it! )

So now I have a nice N800 paperweight.

It can only be recovered with a serial cold flash, if at all. . . Why is it, that after a couple of years now, no one has posted anything on how to do a cold flash? Is it REALLY that difficult? Or is it that there are really that few tablet owners? I've done plenty of JTAG flashes on WRT routers and it's not that hard. So why is it that there is nothing here on serial/jtag stuff?

In the meantime I went ahead and ordered another N800 since Nokia seems notoriously slow in fixing broken tablets. . .

Since I don't think I can kill the dead one any further I'm going to work on making up a serial cable to cold flash the thing. The Maemo wiki has a little info on that, but since there is nothing substantial I have the feeling there has been little success. . .

If anyone has any suggestions besides sending the tablet to Nokia I would greatly appreciate it!

Re: How to (really) brick a tablet - How to recover?
 

I remember seeing the pinout somewhere or another. I think it's as simple as running the flasher in cold-flash mode once you get the cable built.

Re: How to (really) brick a tablet - How to recover?
 

Well, that's a worse story than what I went through today.

I only had a severe lockup that trashed my filesystem. I'm trying an ext3 instead of an ext2 this time.

I hope you can get yours working again.

Pinouts I think are on this page:

http://maemo.org/community/wiki/Flasher_tool_usage

Re: How to (really) brick a tablet - How to recover?
 

I hope. . .

I've seen the serial pinout on the Maemo site. The problem with making a cable is it requires a level translator IC since the levels on the Nokia are 3.3V when standard RS-232 is 12V. The site has links, but they refer to other devices, not Nokia tablets. . .

I would have thought by now that someone would have made a cable and could comment on whether it actually worked and what components they used. . .

I hate being the innovator on something like this since it's very easy to connect to the wrong pin and fry something permanently. At least the thing is already dead, so it would be no big loss.

Re: How to (really) brick a tablet - How to recover?
 

Sorry to hear of your problems. From what I understand, however, ext3 is probably not a very good idea with embedded stuff like the tablet. The journal needs constant writes which will severely reduce the life of the flash memory. If it was me I would stick with ext2 and find the cause of the crash. . . and keep good backups.

I'm rather fortunate in that I have multiple recent backups of everything . . . unless the server they are stored on dies :eek:

Re: How to (really) brick a tablet - How to recover?
 

I think a couple people on #maemo have done it. Might be worth your time to pop in and hang around for a few days to see if you can scare something up (I don't remember off-hand who and am too lazy to dig through the logs—maybe check for "jtag" here).

Re: How to (really) brick a tablet - How to recover?
 

Ok, I'm most likely reaching here but one of the options in the Linux flasher utility is -c fo r cold flash I wonder if something like ./flasher-3.0-static -F RX............... -c -R (instead of the normal -f -R at the end) wouldn't help. Worse case... it does nothing. I've not tried I don't know.... ymWv (your millage WILL vary)

Re: How to (really) brick a tablet - How to recover?
 

Only /dev/mtd0 (bootloader) and /dev/mtd1 (config partition) are critical. Others can be reflashed via USB flasher. Good we have confirmed this may happen :-) But still, are you sure? I was wondering if they are protected or not but never tried. On 770 even kernel partition was protected but on N800 it is not. I still hoped at least bootloader (mtd0) is protected since there is no reason to write there from linux. mtd1 is unprotected since some system tools need to write there.

Anyway I would suggest to search maemo-developers list (but I'm afraid you may not find answer) and post your problem there. Maybe some @nokia.com people will help.

Re: How to (really) brick a tablet - How to recover?
 

I'm just wondering... seen all OS stuff is loaded on the internal SD card, can't you simply make a copy (aka ghost or dd ) of a working SD card and dump it on your SD?

Or is there a other catch?

edit: forget it... internal flash memory... doh...

Re: How to (really) brick a tablet - How to recover?
 

So far it looks like they are NOT protected in any way. I suppose we can take that as a "Good Thing"™, unless of course you accidentally write to it. :o

Even though the tablet is bricked I can pretty much confirm that's what did it. The only other thing I did after attempting to mount a jffs file was to reboot to the MMC. Since that's been done a million times before we know that wasn't it. I then got a WSOD (White Screen of Death) and had to pull the battery to get it to power off. Now it's bricked. . .

If I can get a cable to get the thing working I'd be happy try try to brick it again, using the same (fscked up!) procedure ;)

On another thought:

I was thinking this before, but polossatik got me posting it here now. If you can write to /dev/mtdblock0 then you can certainly also copy it via dd.. . . but then again it's already in the FIASCO image isn't it? That makes it even easier. . . Then somebody can take it and work on disassembling the boot loader stuff so that eventually there will be an OSS version of it, or at least a detailed description of EXACTLY what it does.

A disassembly and outline of the bootloader is badly needed and could come in quite handy! Unfortunately right now I need to work on a cable first!

Re: How to (really) brick a tablet - How to recover?
 

Ok. Here it goes.

All of this stuff seems to be old hat to the embedded guys using other devices besides Nokia tablets. So far, however, nothing much for the Nokia tablets has been posted. I'm mainly posting this stuff here for my own benefit to keep track of what I'm doing, but hopefully others will give it a shot also and post their success (or failure?).

This should be most of the info necessary to cold flash the tablet:

1) First you need a Linux box (or at least a live CD). Then you also need the flasher tool and the pinouts for the tablet, get those at the Maemo Wiki

2) Then you need a 1-Port Serial USB Cable. USB to Serial Adapter with RS-232. You need something with a USB converter chip supported well by Linux. Don't use Silicon Labs CP2102, as they don't support Linux well. You can use either Prolific or FTDI since they are supported well under Linux. Specific devices that work well under Linux are the PL2303 and FT232BM, (that one is noted on the Wiki). There are many cheap cables out there, but since you will need to make certain the RS-232 output is 3.3V, I would suggest using a cable with a chip for which you can find the pinouts and voltage levels. As an example only this one should work. Here is the Prolific PL2303 Product Page. Here are the Prolific PL2303 Datasheets. Using all this you should be able to get a serial connection to the tablet working. USB is needed since a standard serial port is too slow. It would take days to transfer a cold-flash image to the tablet via a standard serial port.

3) Once you have the cable and the datasheet you need to make a connector to mate it to the serial port on the tablet. I haven't got to that point yet since I don't yet have a cable (I'll either buy one locally or mail order for one today), or spring terminals (and a chunk of pcb too) yet and my soldering iron is 3000 miles away :(

I guess it's time to head out to buy a cheap soldering iron. I'll update the thread as things progress. . .

Re: How to (really) brick a tablet - How to recover?
 

So I went out to Fry's and now I have a VERY cheap soldering iron ;)

So back to the thread, I believe we are now on step 3, since I now have a cable! It just so happens Fry's also has a
USB-2925 USB TO 2xDB9 Adapter

It contains a MOSChip MCS7720 controller. There is a link to the datasheet on the product page. You also get an extra DB9 serial port you can use for something else as an added benefit! The MCS7720 outputs at CMOS level 3.3V so it should interface nice with the tablet. You need to bypass the HIN 213 RS232 line level converter on the PCB. Don't go straight out from the 12V DB9 port or that will fry the tablet!

It just so happens the Linux 2.6.23 kernel has the driver (mos7720.ko). There is a question, however, as to whether or not the driver actually works since Google has posters reporting problems. Lets hope the driver is working well in the current kernel. . .

Now it's time to go on to step 4, actually making the connector for the tablet. Unfortunately that requires spring pin contacts like are used on the tablet's battery. I will have to order those online, so it will be a while before step 4 is posted. . .

Re: How to (really) brick a tablet - How to recover?
 

Well maybe the spring pin connector won't take so long to get done :D

After a bit of research I found out the more common name for a spring pin is a Pogo Pin. Unfortunately they are usually available only in very large orders for electronics manufacturers. Fortunately, however, I found a place that has them in small quantities!

Time for FedEx!

Re: How to (really) brick a tablet - How to recover?
 

Lots of good info in this thread! I have a different problem that seems to require a cold-flash (see Vanishing Bluetooth on N800 http://www.internettablettalk.com/fo...ad.php?t=16203 ) and am interested in the progress on this, including a source for small quantities of pogo pins, construction details, and experiences with the cold-flash process and recovery of the bridked unit. The connectors on my N800 are divided into two separate areas (7 & 4 pins), unlike the N770 pictures linked earlier in this thread. Have you figured out the pinouts for this configuration?

Thanks,
Phil

P.S. This could be a business opportunity for some budding techie entrepreneur. I'd sure pay a reasonable price for an N800 serial/FBUS cable, since Nokia refuses to make them available.

Re: How to (really) brick a tablet - How to recover?
 

Unfortunately right now the project is stalled due to the need for PogoPins to interface with the tablets PCB. The only ones available are in large quantity (10,000+) orders. I also don't have any specs for the other pcb test points except the ones in the Wiki. Most likely the others are JTAG interface test points.

Fortunately I have a new tablet to use now. Thus I have to go ahead and send the dead one back. So I will never know exactly what killed the old one. I did, however, have a fun time disassembling the old one. It was rather easy and straightforward process and the same as thoughtfix .

The one interesting item was the PCB backup battery. Also, the RF shielding is via snap on covers which are NOT soldered to the pcb. Therefore it should be a simple procedure if someone wanted to trace the interface pads back to the chip to find the JTAG pinouts.

Maybe some day when I have more time. . .

Re: How to (really) brick a tablet - How to recover?
 

Thanks for the update. I've about decided to return mine for service yet again as it is still under warranty. Nokia customer service again implicitly admitted that the FBUS/serial cables COULD be made available, but declined to do so: "Nokia does not currently offer FBUS cables for consumers. Therefore, if your Nokia N800 Interent Tablet is malfunctioning and you are unable to update the device's software, we recommend that a Nokia authorized technician evaluate your tablet for repair."

Re: How to (really) brick a tablet - How to recover?
 

Hey. I picked up this exact USB to serial adapter to use for a 3.3 volt Linux router project. It has the MCS7720 and two HIN213 chips as you describe.

My question: How exactly do I go about bypassing the HIN213 chips?

Here is photo of the board:
http://flickr.com/photos/24074654@N0...63728/sizes/l/

thanks.