PIC Firmware Data Version 2.2
The PIC could in theory generate 8 output control ‘voltages’ when used with a single DAC
and 8-channel demultiplexer. However, we only use six of them in this version of the
midiDAC firmware:
Output
CV generated
1
Pitch CV
2
Modulation Wheel
3
Note on velocity
4
Pitch bender
5
Aftertouch
6
CC 100
7
Reserved
8
Reserved
The PIC also generates two digital type signals direct from its own ports. These are gate and
slide. The former goes low when any note on is received on the selected midi channel and will
go high when a note off, or key velocity zero, is received. It will briefly blip high in the case of
‘legato mode’ off if a second (or third, etc.) note is pressed whilst others are still held down.
The Slide output will go low if more than one note is active on the selected midi channel. The
slide will go high if there are no overlapping notes.
For both logic outputs, it is expected that the PIC will drive NPN inverting stages. This is to
protect the PIC from improper connections to the true slide and gate outputs. It also provides
the facility to level shift upwards very easily.
A third logic output is also available from the PIC that can drive a midi active LED and
suitable current limiting resistor. This feature is unused in the midiDAC module. This output
goes low for 500mS if any valid midi data is present on the midi port.
6
