7bit signed POT translation

[jackchaos]

I need to create a new pot behavior and I was hoping I could get direction on where to start.

Some of the parameters I need to send with pots have to transmit sysex strings based on the following:

A center detent value would transmit 0x00 (zero)

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move it to the right and it increments to a max value of 0x3f (63) or (+63 7bit signed)

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move it to the left of the center detent it would decrement from 0x7f (127) (-1 7bit signed) down to the min value of 0x41 (64)(-63 7bit signed)

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My synthesizer for the most part, recieves parameter values 0x00 to 0x3f, which is perfect. But for 28 of them I, it expects a signed value for -63 to +63.

Any advise would be greatly appreciated.

[TK.]

Thats easy - just modify the sent value in the following way:

  addlw 0x40

  andlw 0x7f

Best Regards, Thorsten.