3D Printed Macro Pad

#include <Arduino.h>
#include <Keyboard.h>
#include <EEPROM.h>


// Hoisted type definitions
struct PadConfig {
  uint32_t magic;
  uint8_t functionNumber[KEY_COUNT];
};


// Forward declarations
uint8_t defaultFunctionNumber(uint8_t index);
bool validFunctionNumber(int number);
uint8_t hidKeyForFunction(uint8_t number);
void saveConfig();
void loadConfig();
void sendMap();
void handleCommand(char *command);
void serviceSerial();
void sendMappedKey(uint8_t index);

const uint8_t keyPins[] = {2, 3, 4, 5, 6, 7};
const uint8_t KEY_COUNT = 6;
const unsigned long DEBOUNCE_MS = 20;

// Python GUI protocol: GET, SET <1-6> <13-24>, RESET.
// The map is retained in the Pico's flash-backed EEPROM emulation.
const uint32_t CONFIG_MAGIC = 0x4D504144;

PadConfig config;

bool stablePressed[KEY_COUNT] = {};
bool lastSample[KEY_COUNT] = {};
unsigned long lastChangeMs[KEY_COUNT] = {};
char commandBuffer[48];
uint8_t commandLength = 0;

uint8_t defaultFunctionNumber(uint8_t index) { return 13 + index; }
bool validFunctionNumber(int number) { return number >= 13 && number <= 24; }

uint8_t hidKeyForFunction(uint8_t number) {
  switch (number) {
    case 13: return KEY_F13; case 14: return KEY_F14; case 15: return KEY_F15;
    case 16: return KEY_F16; case 17: return KEY_F17; case 18: return KEY_F18;
    case 19: return KEY_F19; case 20: return KEY_F20; case 21: return KEY_F21;
    case 22: return KEY_F22; case 23: return KEY_F23; case 24: return KEY_F24;
    default: return KEY_F13;
  }
}

void saveConfig() {
  EEPROM.put(0, config);
  EEPROM.commit();
}

void loadConfig() {
  EEPROM.begin(sizeof(PadConfig));
  EEPROM.get(0, config);
  if (config.magic != CONFIG_MAGIC) {
    config.magic = CONFIG_MAGIC;
    for (uint8_t i = 0; i < KEY_COUNT; ++i) config.functionNumber[i] = defaultFunctionNumber(i);
    saveConfig();
  }
  for (uint8_t i = 0; i < KEY_COUNT; ++i) {
    if (!validFunctionNumber(config.functionNumber[i])) config.functionNumber[i] = defaultFunctionNumber(i);
  }
}

void sendMap() {
  Serial.print("MAP ");
  for (uint8_t i = 0; i < KEY_COUNT; ++i) {
    if (i) Serial.print(',');
    Serial.print(config.functionNumber[i]);
  }
  Serial.println();
}

void handleCommand(char *command) {
  if (!strcmp(command, "GET")) { sendMap(); return; }
  if (!strcmp(command, "RESET")) {
    for (uint8_t i = 0; i < KEY_COUNT; ++i) config.functionNumber[i] = defaultFunctionNumber(i);
    saveConfig();
    Serial.println("OK RESET");
    return;
  }
  int keyNumber, functionNumber;
  if (sscanf(command, "SET %d %d", &keyNumber, &functionNumber) == 2 &&
      keyNumber >= 1 && keyNumber <= KEY_COUNT && validFunctionNumber(functionNumber)) {
    config.functionNumber[keyNumber - 1] = functionNumber;
    saveConfig();
    Serial.println("OK SET");
    return;
  }
  Serial.println("ERR Use GET, SET <1-6> <13-24>, or RESET");
}

void serviceSerial() {
  while (Serial.available()) {
    char c = (char)Serial.read();
    if (c == '\r') continue;
    if (c == '\n') {
      commandBuffer[commandLength] = '\0';
      if (commandLength) handleCommand(commandBuffer);
      commandLength = 0;
    } else if (commandLength < sizeof(commandBuffer) - 1) {
      commandBuffer[commandLength++] = c;
    } else {
      commandLength = 0;
      Serial.println("ERR Command too long");
    }
  }
}

void sendMappedKey(uint8_t index) {
  Keyboard.press(hidKeyForFunction(config.functionNumber[index]));
  delay(8);
  Keyboard.releaseAll();
}

void setup() {
  loadConfig();
  for (uint8_t i = 0; i < KEY_COUNT; ++i) {
    pinMode(keyPins[i], INPUT_PULLUP);
    stablePressed[i] = lastSample[i] = (digitalRead(keyPins[i]) == LOW);
  }
  Serial.begin(115200);
  Keyboard.begin();
}

void loop() {
  serviceSerial();
  unsigned long now = millis();
  for (uint8_t i = 0; i < KEY_COUNT; ++i) {
    bool samplePressed = (digitalRead(keyPins[i]) == LOW);
    if (samplePressed != lastSample[i]) {
      lastSample[i] = samplePressed;
      lastChangeMs[i] = now;
    }
    if (now - lastChangeMs[i] >= DEBOUNCE_MS && samplePressed != stablePressed[i]) {
      stablePressed[i] = samplePressed;
      if (stablePressed[i]) sendMappedKey(i);
    }
  }
}