....please pass this along to EFI live. This is the serial protocol for the SM-AFR
The iMFD Digital output is
19200 Baud
8 Data Bits
1 Stop Bit
No parity
Packet format is as follows for the SM-AFR
1) Start bit (0x80)
2) Address bit MSB (0x00) for SM-AFR
3) Address bit LSB (0x00) for SM-AFR
4) Instance (0x00) if only one SM-AFR is connected
5) Data MSB
6) Data LSB
7) Stop bit (0x40)
(Packet set repeats exactly every 100mS)
Interpreting the data bits is as follows.
int datamsb;
int datalsb;
int data;
datamsb = datamsb & 0x3F; //This ignores 2 most significant bits
datalsb = datalsb & 0x3F;
data = (datamsb << 6) | datalsb; //data is the AFR value
when data is 0, AFR is 10 (gasoline) = 0.68 lambda
when data is 255, AFR is 20 (gasoline) = 1.36 lambda
when data is 256 AFR is "lean"
when data is 257 AFR is "Air"
All you'll need is a Max232 chip to convert TTL to RS232 levels
_________________
PL
PLX Engineer
www.plxdevices.com