Support for Dishwasher / Miele G 651 SCI Plus

[PatMan6889]

I would like to add support for this Miele Dishwasher:

Mod: G 651 SCI Plus
Nr: 26/63502802
M-Nr: ?
Type: HG01
Production period: 04.2001 - 11.2006

The PC port is inside the salt indicator.
The PC LED is blinking red when I try to scan for keys but I get no response in the program. Also I cannot find out the software ID.

Any idea what I can do?

[medusalix]

This should be an easy one, since the G 651 I PLUS-3 is already supported by FreeMDU. When I worked on this device, I noticed that the PC LED is not very strong, so you might have to be really close to the port for it to work. You can also try increasing the 47 kOhm resistor on the optical adapter, which increases the sensitivity of the receiving diode.

[PatMan6889]

This should be an easy one, since the G 651 I PLUS-3 is already supported by FreeMDU. When I worked on this device, I noticed that the PC LED is not very strong, so you might have to be really close to the port for it to work. You can also try increasing the 47 kOhm resistor on the optical adapter, which increases the sensitivity of the receiving diode.

Thank you, this makes me confident.
Currently I use 22k which was working good with W5873 and T8813C, before I tried 47k and 100k.
Tried again with 68k. Now it is almost impossible to get a connection. Same result as with 100k.

There is a dark cover over the LEDs, maybe it absorbs too much light and I need to expose the PCB.

[medusalix]

I've tried it again today with 47 kOhm and that works fine. I'm currently working on a better design for the adapter though...

[PatMan6889]

@medusalix Worked on a design with some salvaged parts. I will try it out soon.

[rchl]

I only know very basics of electronics so I wonder what's the reason for extra transistors and capacitors that are not in the original design?

[medusalix]

@PatMan6889 I've tried a very similar design with a BC847C, but it turned out that the gain of that transistor is still not high enough to work at baud rates > 9600 baud (to work with some of the newer devices).

[PatMan6889]

I only know very basics of electronics so I wonder what's the reason for extra transistors and capacitors that are not in the original design?

I am self taught in electronics but I try to explain.
Problematic is the RX part. If the phototransistor delivers not enough current we dont reach a sufficient voltage at the input. It can be tuned with the resistor in the original design but has drawbacks like the signal getting weaker. The transistor amplifies the weak signal from the phototransistor. In my schematic R1 should be low as possible because when it is too high we create a kind of capacitor that leads to a larger rising and falling flank. At some point it will be impossible to read the digital signal.
Transistor on TX part is to reduce strain on the IO of the microcontroller. Normally you dont want to drive anything from an IO because it should at max deliver 20mA. With a transistor we can increase the current up to 70mA according to specification, but i still want to keep it lower.
The capacitor is to smooth out ripples on the VCC line but it could be optional when the source is good enough.
I might replace R1 of my schematic with a potentiometer. It should be somewhere between 1k and 10k.