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Hardware prototype for the OTTO Synthesizer by Topisani

prototype rendering 10x10 silicone buttons with led backlight

Main features


  • ILI9341 based TFT 2.8" TFT screen.
  • 4 low profile clickable encoders
  • 40 function keys
  • STM32F103VET6 mcu
  • Raspberry GPIO connector
  • connects to all the various boards
  • expansion headers

Power board

  • 2A 5-16V DC input & 500mah micro usb input
  • MAX8903A 1s Lipo charger IC with path management
  • 5V 2A DC-DC boost converter (TPS61090) & 3V3 700mah LDO (XC6210)
  • MAX17048 1s lipo fuel gauge, connected via i2c to the raspberry
  • pi_power circuit for monitoring and control boot and shutdown routine

Audio Board

  • SGTL5000 Audio Codec
  • Electret microphone amp circuit
  • LM4860 speaker amplifier
  • 1 TRS jack line IN
  • 1 TRS jack line OUT
  • 1 Headphone IN


  • 2 octaves keyboard with 16 keys bottom row
  • expansion headers
  • 16 addressable rgb leds

those specs refer to the tactile buttons version, but a led backlight button version is in the works too.

prototype rendering one of the first design iteration