I successfully unbrick my car !!!
I make some mistake in sm.conf and my system stuck at animated Mazda logo
My luck is:
a) I disabled the watchdog before. So the system is not in reboot loop
b) I not upgrade to 511/512 Firmware. Remaining on 56.230 I know the root password -- THIS IS IMPORTANT !!!
I try before:
- usb->ethernet not work -- I not got link on Ethernet
- usb uninstall not take effect
From external sources I got information about serial console of CMU (pic 1)
I buy a Arduino programmer USB TTL for 2Euro (pic 2)
Test it with a raspberry PI (PI3 have some problem with serial console ! google it).
I go to my favorite car stereo/alarm/GPS service and ask him to solder two wire to RX/TX of CMU (pic 3) + a third wire for ground
That 3 wire cable (RX/TX/GND) I want to be ended at fuse box (pic 4) to be closed in fuse box when not used
Connect it to arduino programmer (pic 5)
Optionally lengthen it with a USB cable and connect it to your laptop (pic 6)
Connect to USB/serial converter's COM port (COM12 for me) with your preferred terminal client software at 115200 8,N,1
I use SecureCRT because have integrated Zmodem transfer
If you press ENTER the system answer with "cmu login:"
You can log in with root / jci like in ssh
like in ssh you can use rz / sz linux commands to receive(send to cmu) or send from CMU multiple files via Zmodem protocol
After connecting to CMU using the serial console, "repairing" is easy.
I my case:
MODIFY sm.conf on my computer with my preferred editor
mount -o rw,remount /
CHOOSE sm.conf on my computer (rz not overwrite existing files)
chmod 755 sm.conf