This hand held throttle is very well supported in Rocrail.
For a small fee Fred Jansen is prepared to program an Atmega8L for you.
Therer are two different incrimental switches.
The different is the way the code is made.
It results sometimes in having the speed control working the wrong way.
Since I never have been able to figure out which is which, the GCA124-8 is equipped with two
jumpers, where the function of the speed control can be reversed.
So if its working opposite, just position the jumpers 90 degrees from wthe actual position and
you will be fine.
A few remarks have to be made to help you being succesfull with the production of this FredI.
Fix the empty PCB with screws in it's future housing, and use it to drill the exact positions of the pushbuttons, SW2 and leds.
Use the pcb as a mould for holes of pushbuttons, leds and SW2.
Pushbutton positions have a little center hole for this purpose.
All other parts can be mounted after that.
The pushbuttons and leds are mounted at the backside of the PCB.
Please take care not to use the center hole of the leds, because that one is only a drilling mould.
After a serious check, connect the pcb , without IC's inserted, to LocoNet. Check if 3,3 volt is correct between pt 7 and 8 in IC1 socket.
The processor in the kit comes with set id number. After insering IC's and startup, the three leds wil indicate a loop constantly.
After pressing all buttons, tuning the knob, and pressing it, the lo0p will stop, and GCA124-8 is ready to go.
After assembling the pcboard, it is better to test the 3,3 Volt power to the processor, before inserting the integrated circuits.
Just connect GCA124_8 to LocoNet and switch Railpower ON.(Important!)
Between points 7 & 8 of IC1 should now show 3,3 Volt.
Firmware can be found here for download: