using mplab with vex

[Foster]

Let me second using the WPILibrary and the MPLab compiler for the Vex. The library does a lot of work for you and makes it very simple to do complex control programming in a few lines. There is very good documentation on all the calls.

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On the serial port question, I've hooked a number of different serial devices to the Vex.

1) Are you sure you have the right voltage levels? The serial ports are at a TTL, not RS-232. When I connected the Garmin GPS I used the orange Vex box to convert the levels. There was also a null modem between the GPS and the orange box.

2) Baud rate - are you sure the baud rates and the bit configurations are set?

3) Are you polling fast enough to get the bits back without a buffer overflow? Do you get framing errors?

Are you using the base code, WPILib or something else?

[DanielR.]

Originally Posted by Foster

On the serial port question, I've hooked a number of different serial devices to the Vex.

I hope you don't mind if I make you my new best friend then. I have been trying to get to this to work for months.

Originally Posted by Foster

1) Are you sure you have the right voltage levels? The serial ports are at a TTL, not RS-232.

Yes both boards operate at TTL levels.

Originally Posted by Foster

2) Baud rate - are you sure the baud rates and the bit configurations are set?

That is one area that I might be having trouble with. I can easily control the baud rate and settings for the ABB, but the Vex is a little more confusing to me. I believe I have it set to No parity, 8 bit transmission, at 115200 baud.

I thought I read that the Vex serial is not inverted, but I can't capture anything from it unless I have the serial input (on the ABB) set to inverted.
Also I can't confirm that information as correct.

Originally Posted by Foster

3) Are you polling fast enough to get the bits back without a buffer overflow? Do you get framing errors?

I am not exactly sure what you are asking. What do you mean by get the bits back? The atom does not have a buffer. It is, of course, possible to make a software driven buffer, but that has its own issues.
By "get framing errors" are you asking if an error flag is being set? I never thought to check for that. When I started on this task I knew nothing about serial communication, nor even very much about PICs.
I am still trying to assimilate all the necessary data, compile it, and integrate it into my knowledge base. I am not a robot.

Originally Posted by Foster

Are you using the base code, WPILib or something else?

By base code do you mean the Vex startup code? If so, then yes. With Kevin Watson's serial_ports stuff involved as well. That was the only way I could find to control the serial comm on the Vex. If there is an easier (or more robust) solution, I would love to hear it.

[Foster]

DanielR. I sent you a private messagewith some code samples in it, did you get it?

Thanks!
Foster

[Nathan]

I wrote a short tutorial on using MPLAB with the WPI Lib here if it helps.