Hi all,

I am trying to make a car monitor with a 16F876. I have a function generator that I am using to simulate the RPM's and speed while measuring voltage to an analog pin through a voltage divider. Later on I will add some other funtions to make it more interesting. This is all working fine on my bench but I have doubts when I try to implement it into the car. Without trying to develop an OBDII interface, because I don't know anything about it, I was going to tie into the pulses from the speed senor and the engine RPM sensor. If I was trying to make this device for numerous types of vehicles, would the calculation for speed and RPM be different for each vehicle? Does anyone know if the values are different for different models by the same manufacturer? If I am going down the wrong path, please chime in and let me know if there is a better way.

Thanks,

Chris