cross-posted from: https://lemmy.dbzer0.com/post/42322761

My broken 15 y/o w/m has a serial port tracing to an atmega32L chip. I have a USB to TTL adapter which is set for 5v (as opposed to 3.3v) using a jumper. The TX, RX pins are connected to the RX, TX pins of the w/m, respectively. The power supply pins (0v & 5v) are left disconnected.

I ran minicom -D /dev/ttyUSB0 -b 9600 on the PC with the w/m powered off. Minicom seems to default to an “8,N,1” configuration. When I power on the w/m, minicom flashes a popup saying something like “no connection to /dev/ttyUSB0”. This is a bit bizarre because if powering the w/m triggers that popup, obviously there is a connection of some kind.

I do not have the service manual for the Beko WMD 26125 T and the mfr “lost” their copy. I have only scraps of service docs for a similar model that were leaked to a shitty manual jailing service. The circuit diagram of these docs label the serial port as “EEPROM” (as pictured). I suspect the ISP port is strictly for flashing (programming) the machine while the serial port is apparently for accessing the storage (to see the error state that is stored and perhaps clear it if I am lucky).

The goal is to confirm that the error code is “5” (my guesswork based on LEDs lit in binary [101]). The ultimate goal is to clear this fucking error off so I can use the machine. All components work when hotwired (motor, pump, inlet valves). I believe the error state is the machine caught in a lie. Normally the error states are cleared by pressing a secret button sequence, which the mfr witholds from the owners so they can charge us hundreds to do simple repairs.

What can I do without help from the manufacturer? Am I left with trying different baud rates and configs? What should I try? The w/m software is obviously a closed source, thus the serial config is kept secret from w/m “owners”.

Anti-repair rumor: manufacturers disable serial ports before shipping to block repair. But that practice may have started after my w/m was made ~15 yrs ago.