have bricked 900c? your 900c suddenly won't power on anymore? here's a solution

i thought i should post this in the cenet section too, not just as a post in original jtag thread.


if your 900 or 900c suddenly stops powering up, maybe after a system crash or just on its own after a reboot, it probably has a corrupt bootloader image, but otherwise perfectly working hardware.
or if you flashed the device in the wrong way (oops) that resulted in corrupt bootloader...

here's the solution.

what you need
- PC with windows (98 or later), or linux works too, but this description applies to windows
- if you are on windows, then also cygwin from http://cygwin.com
- parallel port on PC
- jtag cable, schematics for a working example (very simple!!) here: http://hpcmonex.net/nec900/files/jtag/900c_jtag.jpg
this emulates a wiggler cable... you can also order some more serious type of wiggler but that costs more.
- soldering iron and the right screwdriver to disassemble the 900c
- bootloader files http://hpcmonex.net/nec900/files/jtag/jtagbootloaders1.zip
- jtag tools 0.5.1, here's a version compiled for cygwin: http://hpcmonex.net/jtag900cfinal.zip


steps
1. after you got all the above, disassemble the 900c, hpcnec has a guide here: http://hpcnec.com/cgi-bin/hpcnec.cgi?fid=15&topic_id=1204570453
2. solder the jtag cable to the jtag pins on the 900c like this: http://hpcmonex.net/nec900/files/jtag/nec900c_jtag.jpg and sort out the LPT end on the PC too.
3. now to make the software work... assuming you are on windows, download and install cygwin from http://cygwin.com. when it gets to ask you about which packages to download, leave all that on default except for an extra package you need, it's ioperm under Devel packages.
4. cmd into cygwin\bin and run this command: ioperm -i
5. after that, here is the already compiled jtag tools for cygwin in windows: http://hpcmonex.net/jtag900cfinal.zip. unzip that to cygwin\home\yourusername\jtag. now it's all ready... to start jtag tools, run cygwin from the cygwin icon on desktop or start menu, and from the cmd it opens, issue this command: cd jtag, then issue this command: cd src, finally issue this: ./jtag
6. connect the 900c if you haven't already, and power it up by simply inserting the battery and putting it on AC power as well! type this command: cable parallel 0x378 WIGGLER
(check if your parallel port is indeed on 0x378, in device manager, lpt port, resources) it should say Initializing ...
of course, if you have a non wiggler cable that is supported by jtag tools then use the name of that instead.
7. then type this command: detect
this should tell you your CPU is a PXA255A0. if it doesn't return anything, make sure the device is on AC properly / battery is fully charged
8. next command is: detectflash
that should return lots of info on the flash
9. now try reading your current bootloader image: readmem 0x0 0x80000 filename
you can check its contents or compare it to saboot.nb0 bootloader image to see if it is the same... if not then it's probably corrupt and you have a good chance to revive the device.
10. now if you had cmonex v2.0 rom when it died, you need to issue another command, otherwise not: eraseflash 0x01F00000 4
11. after all this you are ready to flash a new bootloader in. it'll be in two parts until jtag tools is fixed (it is buggy). so you have to flash the bootloader like that. type this command first: flashmem 0x0 sabootpatched01.nb0
12. if flashing and verification was OK, next and last command is: flashmem 0x01F00000 sabootpatched03.nb0
if verification is ok, then you are almost finished now.
13. disconnect from the PC, remove power from 900c, and try reinserting battery and powering up. it should boot up now! if not then maybe something went wrong, try jtag again. note, it's fine if it doesn't boot to OS, just bootloader. just reflash an OS after completing step 14 below!!
14. you should reflash in the normal way, from a CF card, with saboot.nb0 from the jtagbootloaders1.zip after you finished jtagging! otherwise when you flash an OS it'll overwrite second part of bootloader
that's all.


troubleshooting:
1. if verification fails after using flashmem command on 0x01F00000 address, then go to step 10 and use eraseflash command.
2. if cygwin won't run jtag tools then http://www.hpcfactor.com/forums/forums/thread-view.asp?tid=9529&start=16&posts=35 has the solution
3. if you had a 900 running hpc2000 OS then the above posted bootloader will not boot the OS. but the solution is simple: you can choose to keep hpc2000 or upgrade to cenet. if you want hpc2000, then just download http://hpcmonex.net/nec900/files/flash/XIP_hpc2000downgrade-v_6_0_for-cenetbootloader4_10_only.zip
if you want ce.net then download stock cenet rom from http://hpcmonex.net/nec900/download.php (select any of the options except "Not listed" )
flash the image from CF card using C+F method (how to described on my site http://hpcmonex.net).

Edited by cmonex 2008-03-21 2:37 AM

oh and a pic of crappy cable i've used







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IMAGE_001_.jpg (80KB - 9 downloads)

Well, we already know that JTAGging is not pretty.

True, however with two dead units I gotta try
Thanks again for the job, Cmonex

Edited by Dan 2008-03-21 3:04 PM

Cmonex, I was looking at the LPT connector schematics and was wondering what the 25-20 pin on the bottom means. Do I have to connect either the 20 or the 25 pin to the ground, or all the pin from the 20 to 25 or just the 20 and the 25?

Also, are all the diodes of the same kind? And are the restistors of the same kind as well?


Thanks in advance.

Edited by Dan 2008-03-21 4:25 PM

Hi

Dan, On the LPT port pin 20, 21, 22, 23, 24, 25 is grounded. When the diodes is limiting the voltage to 3,3v for cpu logic, a little current flows to the lpt ground pins. Its not a big current but I recommend to solder all of them to ground.

Edited by Ne_Pe 2008-03-21 5:26 PM

Ok, thanks Ne_Pe

yeah, the diode type is specified on the pic

and nepe answered too, i see (he's my friend who i worked with on this jtag)

Two more questions, before starting the job: is it necessary to keep the dislpay and the keyboard ribbon cables connected on the main board while jtagging?

And is this pinout correct?


Edited by Dan 2008-03-23 11:40 AM






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rs232m25.jpg (9KB - 3 downloads)

Dan, that is the DB25 male connector (cable side with pins rather than desktop side) then yes...that is the correct pinout for a parallel port. The desktop side uses the DB25 female (one with the holes) and the top right is pin #1.

Rich

Dan, it's not necessary to keep the dislpay and the keyboard ribbon cables connected on the main board while jtagging

Thank you for all the advices!

Here it is my jtagging cable..soon I'll try to make my 900s come back to life again

Edited by Dan 2008-03-23 3:43 PM






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DSCF0021.JPG (20KB - 7 downloads)

another 900c unbricked. the cable built for it had 200ohm resistors, and was a bit too long, we don't know why it didn't work, my original cable did.

update...

http://hpcmonex.net/nec900/files/bootloader410_nolockcheck_jtag.zip

this is patched to not check for the battery lock on powering on... someone managed to break the lock on a 900c... now if you don't have the patched bootloader already in flash your only option is jtag. but then the device works fine again.

this also has a normal bootloader update file, you can use C+F keys to flash it in. don't forget to reflash bootloader from C+F card after jtagging! use only this file, and not the original official saboot.nb0 or it will again complain about the lock.

so in future no need to worry about the lock.

Edited by cmonex 2008-03-25 3:55 PM

any news Dan?