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System Overview

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okemessi edited this page Sep 4, 2020 · 8 revisions

Features

This device has these functions:

  • 61(by default) piezo key inputs
  • 2 pedal switches & 2 push-button switches inputs (e.g. for sustain, etc.)
  • 2 pedal expressions & 2 faders (analog) inputs (e.g. for volume, etc.)
  • 3-digit 8seg LEDs
  • "Shift" pedal and push-button switches input for various configuration
  • 5pin-DIN MIDI output

System design

These functions are implemented by five 8-bit, one 32-bit MCUs connected by the RS-485 bus, which share the task of sensing and signal processing.

A-D conversion and pre-processing tasks are shared by four MCUs; the 61 keys are divided into four regions (NE, NW, SE, SW: see below), each of which is handled by one 8-bit MCU.

Other input sources are handled by these four MCUs, and LEDs are driven by another 8-bit MCU.

The main 16(32)-bit MCU processes the signals from the four MCUs and generates MIDI messages and LED output.

For specific design, see System block diagram.

Key map

key map

MCU units

For availability, PIC microcontrollers are adopted.

16-bit MCU

  • PIC24FJ64GA002 (without USB)
  • PIC24FJ64GB002 (with USB: you should choose this if you want to add USB MIDI function)

8-bit MCU

  • PIC16F18857 (28-pin, capable of 19 key inputs + 2 Vrefs + 3 UARTs + 3 VCC/VDDs + 1 MCLR)
  • PIC16F18877 (40-pin, capable of 30 key inputs + 2 Vrefs + 3 UARTs + 4 VCC/VDDs + 1 MCLR)

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