Ford J1850 PWM

All,

I am trying to build my own DTC reader, but I have problem with the J1850 PWM now.
I sent command to my Ford Focus with 0x61 0x6A 0xF1 0x04 0x9F. and I got IFR 0x10 no problem, then I sent 0xF1, sometimes, I got the right response with 0x41 0x6B 0x10 0x44 0x53. But most of the time I got nothing or other response which first byte is 0x81...,

Does anyone have the same experience? or tell what is wrong?

Thanks in advance!

Albert

Albert, out of curiosity, why don't you use an off-the-shelf IC that implements J1850 PWM, like an STN1110?

Vitaliy,

I already implemented CAN and Kline by using STM8s, but PWM make me crazy. I think the problem may be from the pulse width is not accuracy. You know I don't like to use the exist IC.

Thanks.

Albert

Anyone see my wheel?