That project has been a journey, V1 used the same Attiny85 board I used to defeat the speed limit of the stubborn Curtis controller in my Excell cart.
After using it for I while I realized it was unnecessarily complex and I could leverage more of the features of the Alltrax to accomplish the task.
The simpler V2 interface worked well and it was a replacement for the FNKS switch, but after using it for a while I decided there was no need for 3 manual modes.
Once I upgraded to Lithium it was also obvious that the fast throttle rate that is fun for forward driving can also be an issue when going in reverse, and I also prefer the cart not to roll freely in reverse when the accelerator pedal is up.
Which bring us to the current compact V3 interface below.
It interfaces with the Alltrax 3-pin FN connector, gets signal and 12v power from the pedal switch, it also taps into the reverse signal so it automatically lowers the throttle rate and adds about 30 amps of pedal up brake in reverse.
I also added another extra input wire for a "mild mode" switch that has some pedal up brake that I mostly use for "hill assist" brake when going downhill with a full cart.
I have enough parts to build a few more and may do that over the holidays for fun.