[Xperia Arc General] scholbert:
how to proceed....

Hi!

No not yet... i tried the usual things while attached to the serial port, no response here.

I guess i'll have to look in the disassembled code from my bootloader RAM dumps, if i could get anything out of it.

Though i'll got less time for research right now...

How to find the UART testpoints on other Xperia 2011 devices

I'll try to give some advice here, how to find the UART testpoints, because there'd been some requests.

Though it's not that easy to tell what i focus on, when i look at a mainboard i'll try to give some guidelines how to start investigation.

1. Would be nice if you got a service manual for your device with schematics and component placements.

(these documents are floating around on the web for some of the Xperia 2011 series)

2. Check your commandline for ttyMSM2 by using cat /proc/cmdline (if it's there it's worth to digg deeper)

3. Install this tool to your Android system: http://code.google.com/p/android-serialport-api/

4. Power down your phone and remove the battery

5. Follow disassembly guides to open up your device and look at the side of the mainboard showing up after opening the back housing.

6. Try to locate the testpoints not covered by stickers or shields first and do something like a visual inspection

7. Exclude the testpoints, you'll find in the schematics (the schematics available, are level 2 and do not include UART testpoints)

8. Make sure you got an oscilloscope at hand to measure waveforms

9. Try to think like an engineer who would design a mainboard for mobiles... i know this sounds little strange but i don't know how to describe it in other words.

(UART testpoints are mostly reduced to RXD/TXD signals and should be found aside each other, at a similar location)

10. Start up your phone with a battery inserted, but with the back housing removed

11. Start the serialport api demo and setup the port to ttyMSM2 @ 115200,8N1

In the main menu there's button for Send 01010101... press this button

12. Turnover the device, use your oscilloscope and try to find a signal toggling between 1.8V and 0V

13. If you think you found it, return to serialport api demo and disable Send 01010101 or at least close the tool

14. Return with your oscilloscope and measure again, the testpoint should stick at 1.8V now.

15. Repeat with step 11 again... untill you are sure that the behaviour of this testpoint follows the Send 01010101 button

16. We just identified the TXD line of UART3... you may solder a wire to this tespoint now.

You may stop here, if you just like to observe the boot process later.

17. Now look at the testpoints nearby for the possible RXD testpoint (which is obviously the harder part and more guessing)

18. Return to serialport api demo and press the button Loopback

19. Take the TXD wire and gently touch testpoints nearby... (you might use a 100Ohms series resistor in addition to your wire)

Attention: Never touch the testpoint used for the s1tool unlock procedure in this step.

It might cause trouble or unresponsive device.

Keep in mind that the functionality of many testpoints are unknown as well. Please be careful!!!

20. By touching the correct testpoint the loopback will report a huge amount of RXD packets counting up with the

TXD packets... Got it!!!

BIG FAT WARNING:

While trying these steps, never ever touch or ground the testpoint used for the unlock process.

While running Android this might leave your device unresponsive or even brick your hardware.

Please be aware, that by following this procedure you might damage your hardware as well at any point.

It's up to you and your knowledge about electronics and the awareness of the complexity of these devices.

I'm not responsible for anything going wrong, by following this guide.

You'd been warned!!!

That's barely it... feel free to leave comments.

Regards,

scholbert