Mapping VEX I/O to FRC code

I want to practice and adjust our FRC code using the VEX. Do you know of a document that explains the mapping of IO that is used in FRC and correlates FRC IOs to the VEX IOs?

When I complied the FRC code in the VEX the following variables were not defined:
‘p1_x’ has not been defined
‘p1_y’ has not been defined
‘p3_wheel’ has not been defined
‘p1_wheel’ has not been defined
‘p1_wheel’ has not been defined

Also on the VEX it says interrupts, how is that mapped to the FRC code. There is a lot I don’t understand between the two.

What are you using for both, EasyC for vex, for FRC or MPLab all the way, with these different options the coding and structure are different so we will need to know what your using b4 we can really help.

You need to look at what those mean, exactly, and translate that to Vex.

p1_x is OI port 1, the “X” direction. This would possibly translate to Channel 1 on the Vex controller. But, of course, you can define it as Channel 3 (which is “X” on the left joystick instead of the right), or anything else you like.

p1_y might be channel 2

The three “wheel” values are the switches on the little thumbstick on the standard KOP joystick. It is also an analog input (like X and Y) and has no equivalent on the Vex controller. Maybe a good use for Channels 3 and 4 or, with some limits, channels 5 and 6.

As a hint, you’d use the “RX Input” block.

Look at this schematic to help in understanding what the joystick does, and then you can think about how to replicate that functionality on the Vex controller.

Note that the FRC OI is a LOT more versatile than the Vex transmitter.


Thanks. It is MPLab all the way. I want to play with our FRC code on a VEX, try various sensors on the VEX before we move it to the big FRC bot.