I am having a few challenges getting my T100MD+ to communicate with an airconditioner control board.
The control board uses a proprietary RS485 protocol which is described as 'half duplex, each byte has 11 or 12 bits: 1 start bit, 8 data bits, 1 even parity check bit, 1 or 2 stop bits. Baud rate is 4800. Each message has 12 bytes: 1 header, 2 address, 2 command, 6 data & 1 check sum'
I use the following commands to set com port 3 at first scan
SETBAUD 3,42 (set RS485 to 8,1,e)
SETPROTOCOL 3,10 (No protocol)
and then use a series of OUTCOMM statements to transmit the required command strings
eg OUTCOMM 3,&H55 (send header 55H to airconditioner)
eg OUTCOMM 3,&H00 (send high address)
eg OUTCOMM 3,&H02 (send low address)
etc....
So far I have not been able to communicate with the control card. When I put an oscilliscope (PO Scope basic) on the RS485 I can decode all of the message except for the header which is being misinterpreted eg 80H instead of 55H
Am I missing the initial start bit because I am in 'no protocol'. Not sure of the implication of '1 or 2 stop bits' in the protocol
Any suggestions welcomed