ANKNOVAMAN, Thanks for the link! Another link from that post:
http://andydoz.blogspot.co.uk/2017/1...ronic-gps.html
It’s nice to see a working example of some code, the similarities show me I’m getting part of it right.
I have considered going this route, but I wanted to retain the mechanical odometer. My ’88 GMC does have a motor for the odometer, so it could be done. I read through this epic thread started by ls1nova71:
http://67-72chevytrucks.com/vboard/s...d.php?t=512751 before I decided to start This thread.
At first I thought about having a motor in a box connected to the speedometer cable. Thanks to Dayj1 for the motor, and Jason Banks for the mounting example now I’m getting the idea that the motor can be attached directly to the speedometer without gear reduction, or a cable.