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markgraham
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Posts: | 5 |
Joined: | January 1970 |
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Post by markgraham on Feb 15, 2018 3:09:52 GMT -5
Hello, This is my first time posting on the forum. I've used the BS2 since 2005 but have not really done a lot with serial communication using SERIN and SEROUT (other than simple LCD displays). Now I've got a new fun project which is to interface with the OBD2 connector in my Honda Civic. The difficulty right now lies in initializing the ECU, which requires transmitting HEX 33 at 5 baud. According to the Stamp manual, the baudmode for the SEROUT command for 5 baud (assume 8 bit no parity inverted) would be 199980 which exceeds 65535, so that won't work. So, I thought I would manually create and time bits via the HIGH and LOW commands (which I later found out is called bit-banging), but I'm not confident that the timing is right and I don't have a scope to verify the signal. PULSOUT will not work either, as the bit length is 200ms (max is 131.07ms on the BS2) I am using a MAX222 line driver to get the outputs up to RS-232 voltage, so the bit bang is sent through this chip, which probably makes things more tricky. So far I have not been able to get a response from the car's ECU... Though there could be other things wrong, does anyone have experience bit-banging at a super low speed like 5 baud? I'd be interested in knowing if there is a better method to pull this off. Thanks everyone!!! I'm also surprised I was able to get the username "n00b" on the forums... who would have guessed? Thanks more details: Software Explainer Video
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