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busy-toad

Intro

Evolution of the digital pedal geekyToad. This page is a list of features/hardware that I would like to implement. Nothing is set in stone of course, but it's just a place to collect interesting stuff and ideas.

System

I/O

  • Two audio instr/line inputs as TRS Jack (differential or single-ended)
  • Two audio instr/line outputs as TRS Jack (differential or single-ended)
  • One stereo output for headphones, hardwired to the two outputs
  • OLED display, power LED, some non-assigned (yet) LEDs
  • A lot of buttons and One rotary encoder with push button
  • Volume knobs for heaphones
  • Two digital inputs as TS Jack (e.g. stomp buttons)
  • Two analog inputs as TRS Jack (e.g. expression pedals)
  • USB C device for power and FS data transfer

Features

  • Two effect chains (primary and secondary)
  • Programmable digital/analog inputs as dynamic controls of effects
  • Drum machine (synth + samples)
  • Chromatic tuner
  • Mixing matrix for effect chains and drum machine
  • Display brightness control

Hardware

DSP MCU - STM32H750VBT6

  • LQFP100 14x14x1.4mm
  • ARM Cortex-M7, 480MHz, FPU, 128kB flash, 1024kB RAM
  • Gotta use the CMSIS-DSP library!!!
  • mouser link

UI MCU - STM32H523CEU6

  • UFQFPN-48
  • ARM Cortex M33, 250MHz, FPU, 512kB flash, 272kB RAM
  • mouser link

CODEC - CS4272

  • same codec on some focusrite scarlet interfaces apparently
  • it just works. no fancy headphone/microphones things. low-power portable electronics are overrated
  • cirrus logic link

Honorable mentions:

  • E.D.'s favorite: tlv320aic3104-21
  • daisy seed's: pcm3060 ti link

FLASH - W25Q512JV

  • w25q512jveim (still on the table!)
  • the quad spi interface with the mcu needs a lot of pins :/

DISPLAY - 3.83" OLED

  • 3.83" OLED module, 320x132, 4-wire SPI, 16 level grayscale
  • looks really interesting and promising, especially for the grayscale control (could have controllable brightness and such)
  • framerate unknow, but still probably better than normal lcd displays
  • buydisplay link
  • ALTERNATIVE: ILI9341 SPI LCD display (the usual basically)

Various notes

  • STM32 Cube IDE because yes.
  • Debugging is done with cortex 4-wire-jtag/swd 10 pin connection.
  • For the Eq: Linkwitz–Riley filters
  • circuitry for codec I/O:
    • INA116: instrumentation amplifier with extremely low input bias
    • INA105 and 106: differential amplifiers with unit and fixed gain
    • INA1620: beast, dual differential signals amp
    • INA321 and 2321: instrumentation amplifiers, also dual channel
    • MCP6001/1R/1U/2/4: low power opamp used in gt
    • Quad Analog Switch/ Multiplexer/Demultiplexer MC74HC4066A
  • For the switching circuitry
    • MC74HC4066A (same as the focusrite, but apparently a little bit noisy)
    • TS5A3157
    • DG409 / DG410
    • MAX4617 (chatgpt likes this)
    • ADG736 (I like this one!) / ADG734 / ADG1606
    • TS5A3157
    • MAX14689
  • Available in lab
    • CA3140 (opamp)
    • MCP6294 (quad opamp)
    • MCP602 (dual op amp)
    • LM358 (dual op amp)
    • LM386N (audio amp)
    • AD623ANZ (opamp dif amp)
    • AD620ANZ (opamp dif amp)
  • Expression pedals are hard man ...
  • I'm extremely dubious about the feasibility of the 48v phantom power for condenser microphones. A solution can be just buying an external mic pre-amp.
  • cool colors, i like them
  • Differences-between-Mic-Line-and-Instrument-level