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 9600on 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.
Respect. 😳
If no luck, you can get universal washing machine boards now - just hook up your bits and it’s right to go.
Thanks for the suggestion. I’ve seen them in Indian YT videos. I’m half tempted but online shopping is mostly a non-starter for me and I don’t suppose I would find that locally. I bought an Arduino clone and some relays, which might be my nuclear option.
https://www.ebay.com.au/itm/405441142984 as a possible example. Dirt cheap.
Best of luck with resetting your current one.
You will absolutely need gnd to be hooked up to get anything out of it. If the baud rate was incorrect, you would probably receive garbage characters rather than nothing at all.
When I connect the ground pin of the adapter to the ground pin of the w/m, the TX and RX LEDs light up (either solid or rapid fire). That must be wrong, no? The tx and rx LEDs should flash when data traverses the circuit. If we could imagine that the w/m is transmitting data nonstop, certainly Minicom is not, so at least the TX LED should have stayed unlit. I could have something dodgy going on with my ground line.
Just a thought but if you have access to an inverter or isolation transformer, you could test the machine without your house wiring being a complicating factor.
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).
Do you have a scope? Can you look at it’s TX pin when you try to talk to it? If you can see any response on the pin you should be able to figure out the baud rate from looking at that.
