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Because I was only running the envelope generator, I didn't install the analog input or trigger output boards, demonstrating the "a la carte" nature of this kind of build.
Wiring is kind of jumbled in this pic. Here it is unscrambled, going CCW around the Teensy, from the lower left
GND to breadboard ground
"0" to TR1 on trigger board
"1" to TR2 on trigger board
"4" to SWB (bottom switch) on UI board.
"5" to SWT (top switch) on UI board.
"6 "to DC (display DC input) on UI board.
"7" to RST (display Reset input) on UI board
"8" to CS (display chip select) on UI board
"9" to RST on DAC board
"10" to CS on DAC board.
"11" to MOSI on DAC and UI boards.
"13" to SCK on DAC and UI boards.
"14" to SWR (right encoder pushbutton switch) on UI board.
"15" to ENCR1 (right encoder 1) on UI board.
"16" to ENCR2 (right encoder 2) on UI board.
"21" to ENCL2 (left encoder 2) on UI board.
"22" to ENCL1 (left encoder 1) on UI board.
"23" to SWL (left encoder pushbutton switch) on UI board.
Vin to +5V on breadboard.
The DAC and UI boards are powered (and grounded) from their dedicated 8-pin power connectors, but I added redundant ground connections from the DAC and UI boards to the breadboard ground, to help reduce the path between the Teensy ground and those boards' grounds. The trigger board doesn't use any power, and it gets its ground connection from the mounting posts, but I added a redundant ground for the same reason.
DAC and trigger module schematics are on the board pages. The user interface board:
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