Wallas Diesel Heater Serial Interface and Protocol

[dalsgaard]

Hi, I've been searching everywhere for information on the serial interface and protocol to have my onboard Raspberry Pi talk to my Wallas 22gb Diesel heater. I can buy a GSM modem like thing from Wallas, but I'd prefer to have everything aboard run through my Pi - let SignalK be my switch board.

But I'm having trouble obtaining information about the interface. Through some digging I've figured out which pins on the control interface are Tx and Rx, and I've managed to get the control panel send me:

AT+WALLAS=3,0,35,24

Which is a huge success, but still not quite good enough :-)

Above seems to be sent using 115200 8N1 - quite fast actually, but otherwise quite standard. I've just hooked up a CP2102 UART and I believe this one delivers no more than 3.3V on transmit. That might be too low for the Wallas control panel to pick it up.

Does anyone have information about this serial interface? Will I need to find an FTDI that can do 5V on transmit?

Also, does anyone know of the protocol needed here? I would assume that the Wallas 4430 GSM unit more or less acts as a GSM modem, but it does have some relays, so perhaps it's more than just that.

I've tried sending 'OK\r\n' back to the control panel, but it still just keeps repeating the above line (then again... if it can't 'hear' me...)

Any advice would be much appreciated.

I have contacted Wallas for information about the interface and the protocol, but have gotten no answer (so far...)

[dalsgaard]

Aha, so I tried with a USB FTDI UART and couldn't get that one to work at all. Switched back to the CP2101 and after some restarts of the heater finally managed to get the AT+WALLAS messages back again.

It seems that protocol is a bit different that I thought though.

I can send 'START' and 'STOP' and make the heater correspond to that.

Four numbers returned are somewhat related to the temperature and desired temperature in the cabin...

[dalsgaard]

So, a line like this:

AT+WALLAS=3,0,35,24

Seems to show: operation mode, heater enabled, desired temperature, current temperature.

Unit replies AT+WALLAS=0 to commands it understands, and currently I've found the following commands:

START
STOP
TEMP=x

Where x is a positive integer, temperature in Celsius.