MIDI-Host-Adapter/MIDI-Host-Adapter.ino

/*
   MIDI-Host-Adapter

   (c)2023 H. Wirtz <wirtz@parasitstudio.de>

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software Foundation,
   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301  USA
*/

#include <TM1638plus_Model2.h>
#include <elapsedMillis.h>
#include <limits.h>
#include <EEPROM.h>

#define STROBE_TM 9
#define CLOCK_TM 8
#define DIO_TM 7
#define MIDI_CH_BIT3 3
#define MIDI_CH_BIT2 4
#define MIDI_CH_BIT1 5
#define MIDI_CH_BIT0 2

bool swap_nibbles = true;
bool high_freq = false;

#define BRIGHTNESS 6
#define INITIAL_MIDI_CHANNEL 1
#define BUTTON_DEBOUNCE_TIME_MS 150
#define BUTTON_DOUBLE_PRESS_MS 250
#define BLINK_FREQUENCY_MS 500
#define EEPROM_ADDRESS 0x42

// Constructor object
TM1638plus_Model2 tm(STROBE_TM, CLOCK_TM, DIO_TM, swap_nibbles, high_freq);
elapsedMillis button_debounce_timer;
elapsedMillis blink_timer;
uint8_t actual_channel;
uint8_t new_channel;

void setup() {
  Serial.begin(9600);
  delay(50);

  Serial.println("<SETUP>");

  tm.displayBegin();
  tm.brightness(BRIGHTNESS);
  tm.DisplayStr("MIDIHOST", 0);

  uint8_t tmp_channel = EEPROM.read(EEPROM_ADDRESS);
  if (tmp_channel & 0xf0 != 0xf0) {
    actual_channel = 1;
    Serial.println("Setting channel to 1");
  } else {
    actual_channel = 0x0f & tmp_channel;
    Serial.print("Reading channel from EEPROM: ");
    Serial.println(actual_channel, DEC);
  }
  new_channel = actual_channel;

  pinMode(MIDI_CH_BIT3, OUTPUT);
  pinMode(MIDI_CH_BIT2, OUTPUT);
  pinMode(MIDI_CH_BIT1, OUTPUT);
  pinMode(MIDI_CH_BIT0, OUTPUT);

  SetMidiChannel(INITIAL_MIDI_CHANNEL);

  delay(500);

  tm.DisplayDecNum(actual_channel, 0, false, TMAlignTextRight);

  Serial.println("</SETUP>");
}

void loop() {
  uint8_t button;

  button = tm.ReadKey16();

  if (button > 0 && button != actual_channel && button_debounce_timer > BUTTON_DEBOUNCE_TIME_MS) {
    if (button != new_channel) {
      // Button pressed once
      Serial.print("Button once: ");
      Serial.println(button, DEC);
      button_debounce_timer = 0;
      blink_timer = 0;
      new_channel = button;
      tm.DisplayDecNumNibble(new_channel, actual_channel, 0, false, TMAlignTextRight);
    } else {
      // Button pressed twice
      Serial.print("Button twice: ");
      Serial.println(button, DEC);
      actual_channel = new_channel;
      EEPROM.update(EEPROM_ADDRESS, 0xf0 | actual_channel);
      SetMidiChannel(actual_channel);
    }
  }

  if (actual_channel != new_channel) {
    if (blink_timer > BLINK_FREQUENCY_MS) {
      blink_timer = 0;
      tm.DisplayDecNum(actual_channel, 0, false, TMAlignTextRight);
    } else if (blink_timer > BLINK_FREQUENCY_MS / 2) {
      tm.DisplayDecNumNibble(new_channel, actual_channel, 0, false, TMAlignTextRight);
    }
  } else tm.DisplayDecNum(actual_channel, 0, false, TMAlignTextRight);
}

void SetMidiChannel(uint8_t channel) {
  if (channel < 1 || channel > 16) {
    Serial.print("ERROR: MIDI channel number out of range: ");
    Serial.print(channel, DEC);
    return;
  }
  Serial.print("Setting MIDI channel to: ");
  Serial.print(channel, DEC);
  channel--;
  Serial.print(" (");
  printBinary(channel, 4);
  Serial.println(")");

  digitalWrite(MIDI_CH_BIT0, channel & 0x00);
  digitalWrite(MIDI_CH_BIT1, channel & 0x01);
  digitalWrite(MIDI_CH_BIT2, channel & 0x02);
  digitalWrite(MIDI_CH_BIT3, channel & 0x08);
}

void printBinary(uint32_t value, uint8_t len) {
  for (uint8_t b = len; b > 0; --b) {
    Serial.print((char)('0' + ((value >> (b - 1)) & 1)));
  }
}