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. . .

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. . .

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

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!

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.

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. . .

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."

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.