[Second Series]

Thanks for the links, nsocwx, that’s quite a bit of information to digest. It looks like you have a working solution. I’ll be using a DRAC, and I found that when I connected the speedo driver to my ’90 chevy on the 2kppm line to the ECM it may have caused problems with the ECM, I’m not sure, it seemed hard to start. The 128kppm signal goes to the RWAL module so I’m less concerned with that. I could use any of the signals as there is a dedicated line for the speedo on the DRAC module. The LM2907 is set for operating range with a capacitor. The output is a voltage, for my Arduino I don’t want to go above 5v, so I use a 5v supply. The output is 0 to 3.98v with 3.98v at 4kHz with a 2200pF cap. The voltage is fed to an Analog in and scaled to 1023. This is read every iteration. There was some fluctuation so I add the reading to itself for a number of iterations and then divide by that number and get a smooth reading. The 0 to 1023 value is converted to the input frequency through an equation.

I just got that working by itself last week, and will set one up for the optical frequency and then implement both in the main code. I’m using a bench signal generator for now, eventually I’ll try it with the vehicle signals. I want to get away from using interrupts. I could also use the chip registers to count frequency, but that’s a whole other can of worms I’ll avoid for now. The issue is with reading more than one frequency. The motor encoder is one frequency, and the control signal is another frequency. I don’t know if using registers will work with more than one frequency input.