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.
That's some dedication. You checked all the actuators, but did you check the sensors as well? A speculation might be that, if one of them is busted, the controller stalls in error. I'm not sure what the story is with minicom reporting the serial being unavailable but if you have another microcontroller on which you could enable serial, you might be able to see more details. From my own experience, I would wire up a Raspberry Pi Pico, let it run Micropython REPL via USB to see if it catches anything at all. This way you are monitoring the serial before it goes through USB and the OS.
Since the error code possibly implies a drain pump issue, the pressure fill switch would be related. There is continuity across the two pins that are not taking voltage input. When I blow into the hose, the resistence make no change. But I guess it's not a proper test. I think I need to buy a multimeter that has a frequency (Hz) function to see if the frequency changes as the water level fills.
I tested the USB to TTL adapter itself by jumping the TX and RX pins. When I type something into Minicom the character echoes back. I could perhaps try to talk to an Arduino clone (which I have on hand).