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[on:]

I'm a MIDI guitarist, and as such I don't have one thing that all keyboardists have: a modulation wheel.  I have started a project to build a modulation wheel into an expression pedal.  The expression pedal itself is nothing more than a potentiometer, which I have wired to an analog input on my Arduino.  I have successfully written code which outputs MIDI notes depending on the position of the expression pedal, but when I modify that very same code to output modulation instead, it either doesn't work or it changes my sound module's patch.

Here's my current code.  What you need to know is that the sound module is set to MIDI channel 1.  Anyone see something I've missed?

const int expressionPin = 1;
const int controlCmd = 0xB1;
const int modulationCmd = 0x01;
int expressionVal = 0;
int oldVal = 0;
int newVal = 0;

void setup() {
  Serial.begin(31250);  //MIDI Baud Rate

}
void loop() {
  expressionVal = analogRead(expressionPin);
  newVal = map(expressionVal, 0, 1023, 0x00, 0x5F);
  if (newVal != oldVal)
  {
    writeModulation(newVal);
    oldVal = newVal;
  }
}

void writeModulation(int val)
{
  Serial.print(controlCmd, BYTE);
  Serial.print(modulationCmd, BYTE);
  Serial.print(val, BYTE);
}

[Reply #1 on:]

Don't you want to send 0xB0 for channel 1 instead of 0xB1?

If the code works (and it looks like it should) for sending out note data, then I'm afraid it's the receiver that is misinterpreting something. Is it possible you're sending new values just a little too fast? Try putting in a delay in your loop for just a few milliseconds.

--
Beat707: MIDI drum machine / sequencer / groove-box for Arduino

[Reply #2 on:]

OK so it's working now.  If, by any chance, any of you own a Parker MIDI Fly, a word of caution: changing the position of the MIDI mode or MIDI octave switches on your instrument resets the modulation value to zero - and on a Moog Slim Phatty, this means having to re-twist the knob to reflect the maximum modulation you want.

Thanks for your help, RuggedCircuits!