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Gamma Hardware Controls & Peripheral Driver Reference

This skill documents how to interface with all front-panel user interface controls on the this.is.NOISE Gamma Mini Synth, powered by an embedded Electro-Smith Daisy Seed 2 DFM (ARM Cortex-M7 @ 480 MHz, STM32H750IBK6).

It synthesizes findings, drivers, and timing architectures validated in:

Pin Definitions & Header Location

All hardware pin assignments, peripheral channel constants, and polarity inversion flags are centralized in the shared header provided by the Gamma Pinout Skill:

Front-Panel Controls Summary

Peripheral Group Controls Daisy Seed Pins Bus / Interface Software Inversion Reference Guide
OLED Display 1.3" 128x64 Monochrome D11 (SCL), D12 (SDA) I2C1 @ 0x3D (1 MHz) N/A Display Reference
Potentiometers 4 Top Knobs (Chord/Notes Vol & Filter) D18, D17, D19, D20 ADC1 (Ch 7, 5, 3, 11) Inverted (1.0 - raw) Analog Inputs Reference
Left Joystick LX (Mod/Pitch), LY (Mod/Pitch) D22, D21 ADC1 (Ch 19, 4) LX: Normal, LY: Inverted Analog Inputs Reference
Right Joystick RX (Filter/FX), RY (Filter/FX) D24, D23 ADC1 (Ch 17, 18) RX: Inverted, RY: Inverted Analog Inputs Reference
Note Keys 7 Tactile Switches (N1–N7) D1–D7 Discrete GPIO w/ Pull-up Active-Low (0 = Pressed) Digital Keys Reference
Chord Keys 7 Tactile Switches (C1–C7) D8–D10, D13, D14, D26, D27 Discrete GPIO w/ Pull-up Active-Low (0 = Pressed) Digital Keys Reference
Rotary Dial Quadrature Encoder & Push Switch D15 (A), D16 (B), D28 (Click) GPIO Pull-up / FSM 4 transitions / detent Rotary Encoder Reference

Reference Guides Directory

Consult the detailed topical references below for full code snippets, electrical characteristics, and timing constraints:

  1. OLED Display (SSD1306 on I2C1)
  2. I2C1 force-reset sequence (__HAL_RCC_I2C1_FORCE_RESET) to recover from soft-reboots.
  3. Fast Mode Plus (I2C_1MHZ) configuration and pin assignments (PB8/PB9).

  4. Frame refresh budgeting and working around the ~9–10 ms blocking transmission hazard.

  5. Analog Inputs: Knobs & Joysticks (ADC1)

  6. Multi-channel AdcChannelConfig setup for 8 user controls + 1 auxiliary channel (D31/PC2).
  7. Potentiometer polarity sweep (3.3V CCW -> 0V CW) requiring software inversion.
  8. Joystick axes breakdown and why Right Stick X is reversed on the PCB.

  9. Deadband filtering for knobs vs. responsive exponential smoothing (iir = 0.05f) for joysticks.

  10. Digital Keypad: 14 Tactile Switches

  11. Physical layout: 7 Note keys (left grid) and 7 Chord keys (right grid).
  12. Active-low electrical configuration with internal pull-ups (INPUT_PULLUP).
  13. Fast 1 kHz debouncing via daisy::Switch (8–10 ms response time).

  14. Lock-free ring buffer event queue for transferring key events to the main thread.

  15. Rotary Encoder & Integrated Push Switch

  16. Quadrature Gray code lookup table decoding 4 state transitions per mechanical detent click.
  17. Why polling the encoder in the main loop drops pulses during OLED refreshes.

  18. 1 kHz hardware timer configuration (TIM5 @ 240 MHz APB1 clock).

  19. Complete Integration Architecture & Main Loop Blueprint

  20. End-to-end firmware boilerplate integrating all controls into a non-blocking architecture.
  21. Initialization sequence: speaker mute (PC3 driven LOW during boot, unmuted HIGH after audio start), display reset, ADC start, and timer start.
  22. Main loop event processing, encoder delta dispatch, analog polling, and throttled display rendering.

Diagnostic Checklist & Troubleshooting

Symptom Cause Solution Reference
OLED blank or frozen on reboot I2C bus locked up by previous transfer Display Bus Reset
Knob values decrease when turned CW Potentiometer wiper sweeps from 3.3V at CCW Knob Inversion
Right stick X moves opposite to Left stick PCB trace routing reversed on right stick Stick Polarities
Rotary encoder misses clicks while turning Main loop blocked by oled.Update() (9–23 ms) 1 kHz Timer Architecture
Keys feel sluggish or drop quick presses Low polling rate in main loop 1 kHz Key Debounce
Synth locks up / note plays forever libDaisy Logger blocked in TransmitSync after terminal closed Gamma Pinout USB CDC
Buttons and encoder stop responding / freeze Audio callback overload / runaway DSP voice starving TIM5 ISR (NVIC priority 15) Avoid undamped DaisySP models (AnalogBassDrum > 90 Hz), gate idle voices, and enforce maximum lifetime ceilings on activity gates