CAT 3208 monitoring

[Ray Davis]

I would NOT choose PID 255. PID 255 is a continuation PID, which indicates the next byte is a PID in the range of 256 to 511.

The PID's are arranged in an order, single byte data PID's run from 0 to 128. Double byte PIDs run from 128 to 191, and variable byte parameters run above this. This is all modulo 256, and a PID of 255 indicates an extension PID, and the next byte indicates the PID. It can be extended 3 times to give PID values up to 1024.

I don't know how Silverleaf expects you to do this, but I would assume you need to chose a PID that does not get sent in your vehicle. In that case I would chose something like 180, which is normally trailer weight, but would be a two-byte data value.

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PS: Are you looking for actual speed, or the fact that you're on high or low setting. PID 26 is already defined as "Estimated Percent Fan Speed", but expects a percentage value, so it is a single byte value. Never-mind, I see from your example that you are going to send the actual RPM, so a two byte data PID is more appropriate.