PiSynth GPIO pin map

Raspberry Pi 3B · 40-pin header · all hardware controls

GPIO	Pin #	Control	Role	Notes
Reserved — power · I2C · SPI
—	1	3.3V power	VCC for encoders / OLEDs	shared rail
—	2	5V power	VCC for TCA9548A	5V rail
—	6, 9, 14, 20, 25, 30, 34, 39	GND	Ground for all components	multiple GND pins available
2	3	I2C SDA	OLEDs via TCA9548A multiplexer	shared I2C bus
3	5	I2C SCL	OLEDs via TCA9548A multiplexer	shared I2C bus
10	19	SPI MOSI	Colour TFT display data	ST7789 / ILI9341
11	23	SPI SCLK	Colour TFT display clock	ST7789 / ILI9341
8	24	SPI CE0	Colour TFT chip select	CS pin
25	22	TFT DC	Colour TFT data/command select	data/cmd pin
24	18	TFT RST	Colour TFT reset	reset pin
Selector encoder — module navigation
17	11	Selector encoder	CLK	pull-up, interrupt
18	12	Selector encoder	DT	pull-up, interrupt
27	13	Selector encoder	SW — push to change page	pull-up
Parameter encoders 1–4
5	29	Encoder 1	CLK	pull-up, interrupt
6	31	Encoder 1	DT	pull-up, interrupt
13	33	Encoder 1	SW — push to reset to default	pull-up
19	35	Encoder 2	CLK	pull-up, interrupt
26	37	Encoder 2	DT	pull-up, interrupt
21	40	Encoder 2	SW — push to reset to default	pull-up
20	38	Encoder 3	CLK	pull-up, interrupt
16	36	Encoder 3	DT	pull-up, interrupt
12	32	Encoder 3	SW — push to reset to default	pull-up
7	26	Encoder 4	CLK	pull-up, interrupt
1	28	Encoder 4	DT	pull-up, interrupt — avoid if HAT EEPROM conflict
0	27	Encoder 4	SW — push to reset to default	pull-up — avoid if HAT EEPROM conflict
Waveform selector · toggle switches · buttons
22	15	Wave selector	Position A — sine	common terminal to GND
23	16	Wave selector	Position B — sawtooth	common terminal to GND
4	7	Wave selector	Position C — square	common terminal to GND
14	8	Toggle 1	On/off — filter bypass	pull-up, read state on change
15	22	Toggle 2	On/off — OSC sync	pull-up, read state on change
9	21	Patch ▲ button	Next patch	pull-up, momentary
11	23	Patch ▼ button	Previous patch	pull-up, momentary

Notes

All encoder CLK and DT pins use pull_up_enable=True with interrupt-driven callbacks via RPi.GPIO.add_event_detect() — do not poll in a loop.

GPIO 0 and 1 (pins 27/28) are normally reserved for HAT EEPROM. If you hit conflicts, swap Encoder 4 DT/SW to GPIO 9/11 and move the patch buttons to spare pins.

Waveform selector: common terminal to GND, each position pin pulled high internally. Read which pin is LOW to determine the selected waveform. Add a 4th position (triangle) by adding one more GPIO pin.

Toggle switches: wired between GPIO pin and GND, pull-up enabled. GPIO LOW = switch closed = ON.

Total GPIO used: 26 pins — within the Pi 3B’s available GPIO count.

Pisces

Pisces Hardware List

PiSynth GPIO pin map