Full Overview Schematic
Calculations are mostly done on this document!
Mainboard
ScreenSlave Board
Connects the Teensy to everything else. Has some pulldown resistors for the matrix input and a level shifter to communicate with the 5v nano.
Everything else is basically just headers.
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Arduino Nano gets commands and offloads visual output functions (screen and indicator LEDs)
Uses a PWM pin and an & gate to toggle pulsing LEDs on and off (with individual digital signals) for power saving.
Outputs to an I2C HD44780 backpack via the 2nd 4 pin header.
Audio Board
Matrix Body Board
An input board for a matrix-style setup. Diodes are on board as opposed to inside the switch to make it so you can flip the headers with no ill effects. Pull down resistors are on the mainboard so disconnected switches won't float.
1 to 3v3 and 0 to GND activates MIDI mode, Reset and MIDI go to microcontroller. Outputs to audio amp (female header) and 3.5mm jack (male 3 pin header).
Amp shutdown signal goes out to ScreenSlave board to be able to toggle the amp indicator LED on and off. The 2 pin header connects to a toggle switch, and when connected will turn off the amplifier.
Matrix Neck Board
A neck assembly board that can be reused for the other inputs as well. Diodes are on board as opposed to inside the switch to make it so you can flip the headers with no ill effects. Pull down resistors are on the board itself so disconnected switches won't float.
Analog Input Board (V2)
Breaks out to a bunch of 3 pin headers that can be plugged into trimpots/joysticks.
Joystick Single Axis Breakout Board (V2)
A board to break out a standard game controller joystick and only capture 1 axis. To be used for whammy bar
Power/Data Input Board
Midi Transmitter Board (V2)
A little breakout board that gives some sturdier screw terminal connections - also leaves ID floating, important because I'm using a modded OTG cable in my prototype.
MIDI Transmitter - I might revisit this and use an op amp comparator to drive it, would reduce the footprint but might raise current draw a bit.
I used the CD4081N because I had one on hand and it has a low power usage when on (<1mA) because it's a CMOS device.
Not pictured - ground pour
Active transmitting current is ~7mA
Non-transmitting current is ~.5mA