Battery-powered polyphonic synth designed to be a companion to small Midi keyboards.

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Portami is a portable, battery-powered polyphonic synth built around a SAMD21 microcontroller. It's designed to be a companion to small Midi keyboards.

The software is a fork of Marcel Licence's excellent code:

My implementation focuses on USB Midi communication (Midi-in through the onboard USB-C port) and features a push button to cycle between wave types (sine, saw, square, pulse, triangle, and noise). An RGB led inside the button changes color according to the current wave type.

Other than the onboard speaker driven by an LM386 amplifier, Portami has a 3.5" mini-jack port to plug a pair of headphones. The audio socket has a switching mechanism, disconnecting the speaker when in use.

The whole setup is powered by a 3.7V, 1100mAh li-ion battery, recharged and protected by a TP4056 USB-C charger module. A regulator boosts voltage to 5V, providing power to the Midi keyboard.

  • 1 × Seeed Studio XIAO SAMD21 (Seeeduino XIAO)
  • 1 × TP4056 battery charger module
  • 1 × 18650 or equivalent lithium battery
  • 1 × Voltage regulator (like boost converter MT3608)
  • 1 × LM386 audio power amplifier IC

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velix wrote 01/04/2023 at 08:22 point

Great Project, I like it!
Just seen, that the potentiometer can pull the output of the SAMD21 to ground, when on zero position, so it shorts the output pin. I suggest feeding the signal output to one end of the potentiometer and the other end to ground, while picking up the signal from the slider pin and feeding it to the LM386.

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Turi wrote 01/04/2023 at 12:46 point

That's a mistake in the schematic, thank you for spotting it!
I'll update it shortly.

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