synthiota

Pico/Pico2-based board for playing with synthesizers in CircuitPython.

synthiota1_demo0.mp4

Video demos:

• "tbish" TB-303 like synth, demo2: https://youtu.be/MjE2wdevc3M
• "tbish" TB-303 like synth, demo1: https://youtu.be/O4a5pk78DVM

Assembling

The PCBAs come with all SMD parts assembled. The components you will need to supply:

• 1 x Raspberry Pi Pico 2
• 1 x PCM5102 I2S Stereo DAC
• 1 x SH1106 128x64 1.3" SPI OLED
• 2 x PJ320A 3.5mm stereo jack
• 8 x RK09K 10k vertical potentiometer (or similar)
• 1 x EC11 rotary encoder

You will also need some headers and header sockets to attach the modules to the PCB. If using the enclosure, the top part expects the header arrangement to be:

• Pico:
  • Standard header pins on Pico (Pico H sold w/ these pins soldered)
  • Short socket headers for Pico on synthiota board
• OLED display:
  • Standard header pins on OLED display (usually sold w/ these pins soldered)
  • Short socket headers for OLED display on synthiota board
• PCM5102 I2S DAC
  • Standard header pins on PCM5102 I2S DAC board (usually sold w/ these pins soldered)
  • I2S DAC w/ header pins is soldered directly to the synthiota board, no socket

(most links are Amazon affiliate links)

Pico pins used

CircuitPython naming. See hwtest/synth_setup_synthiota.py for how they're used.

Encoder

• board.GP28 - encoder B pin
• board.GP27 - encoder A pin

ADC input for pots

• board.GP26 - ADC input for pot knobs

I2S DAC

• board.GP22 - I2S DAT pin to PCM5102 DAC
• board.GP21 - I2S LCK pin to PCM5102 DAC
• board.GP20 - I2S BCK pin to PCM5102 DAC

Encoder switch

• board.GP19 - encoder SW pin

NeoPixel LEDs

• board.GP18 - NeoPixel LEDs pin

UART MIDI In/Out

• board.GP17 - UART RX pin to MIDI input
• board.GP16 - UART TX pin to MIDI output

SPI for display

• board.GP13 - SPI DC for SH1106 display
• board.GP12 - SPI RES for SH1106 display
• board.GP11 - SPI MOSI for SH1106 display
• board.GP10 - SPI SCK for SH1106 display

Pot mux select

• board.GP9 - SEL A pin to 4051 mux for pot knobs
• board.GP8 - SEL B pin to 4051 mux for pot knobs
• board.GP7 - SEL C pin to 4051 mux for pot knobs

I2C for MPR121 touch sensors

• board.GP3 - I2C SCL to MPR121 touch sensors
• board.GP2 - I2C SDA to MPR121 touch sensors

Free pins: GP0,GP1, GP4,GP5,GP6, GP14,GP15. Feel free to use for other purposes.

Schematics