The VEX ‘PIC Microcontroller’ is usually programmed using the Programming Hardware Kit. This consists of a USB to serial converter (Prolific IC) and a so-called ‘Programming Module’.
The Programming Module contains an RS232 to TTL level shifter IC, a push-button switch and a PIC 12F629 microcontroller. The 12F629 monitors the push button and serial communications, and sends reset signals to the VEX unit when appropriate.
Make Your Own
I made a functional VEX programmer with a MAX232 and an ATTiny45 microcontroller.
Source Code for WINAVR
The project source code is not very polished at this stage, but it does work.
- U1 is an ATTiny45 but any Tiny AVR should do.
- U2 is a MAX232 or equivalent
- 5V VCC is provided by the VEX Microcontroller
- All capacitors are 100N
- R1 is 10K
If you need help building your own VEX programming cable I may be able to assist you.