/*
 * 4x6 ICP Matrix Scanner - Blue Pill (STM32F103C8T6)
 *
 * Layout (electrical):
 *   Col:    0     1     2     3     4     5
 *   Row 0:  T1    T2    T3    T4    T5    T6      <- top strip
 *   Row 1:  1     2     3     ENT   --    --      <- keypad row 1
 *   Row 2:  4     5     6     RCL   --    --      <- keypad row 2
 *   Row 3:  7     8     9     0     --    --      <- keypad row 3
 *
 * Pin map:
 *   Columns (OUTPUT, idle HIGH): PB0, PB1, PB10, PB11, PB8, PB9
 *   Rows    (INPUT_PULLUP):      PB12, PB13, PB14, PB15
 *
 * Free matrix slots (rows 1-3, cols 4-5) reserved for the 4 encoder
 * push-buttons we'll add later. Until then those slots are unwired
 * and will simply never trigger.
 *
 * Output: prints "<label> PRESSED" / "<label> released" at 115200 baud.
 * Keyboard shortcuts in Wokwi: q-y for top strip, 0-9 for keypad,
 * n for ENT, c for RCL.
 */

constexpr uint8_t NUM_ROWS = 4;
constexpr uint8_t NUM_COLS = 6;

const uint8_t COLS[NUM_COLS] = { PB0, PB1, PB10, PB11, PB8, PB9 };
const uint8_t ROWS[NUM_ROWS] = { PB12, PB13, PB14, PB15 };

// Empty string = unwired slot (won't print)
const char* BTN_LABEL[NUM_ROWS][NUM_COLS] = {
  { "T1", "T2", "T3", "T4",  "T5", "T6" },
  { "1",  "2",  "3",  "ENT", "",   ""   },
  { "4",  "5",  "6",  "RCL", "",   ""   },
  { "7",  "8",  "9",  "0",   "",   ""   }
};

const unsigned long DEBOUNCE_MS = 10;

bool          rawReading[NUM_ROWS][NUM_COLS]   = {{false}};
bool          stableState[NUM_ROWS][NUM_COLS]  = {{false}};
unsigned long lastChangeMs[NUM_ROWS][NUM_COLS] = {{0}};

void setup() {
  Serial.begin(115200);
  unsigned long t0 = millis();
  while (!Serial && (millis() - t0) < 2000) { /* wait for host */ }

  Serial.println();
  Serial.println(F("4x6 ICP matrix scanner ready."));
  Serial.println(F("Top strip: q w e r t y"));
  Serial.println(F("Keypad:    1-9, 0, n=ENT, c=RCL"));
  Serial.println();

  for (uint8_t c = 0; c < NUM_COLS; c++) {
    pinMode(COLS[c], OUTPUT);
    digitalWrite(COLS[c], HIGH);
  }
  for (uint8_t r = 0; r < NUM_ROWS; r++) {
    pinMode(ROWS[r], INPUT_PULLUP);
  }
}

void loop() {
  for (uint8_t c = 0; c < NUM_COLS; c++) {
    digitalWrite(COLS[c], LOW);
    delayMicroseconds(5);

    for (uint8_t r = 0; r < NUM_ROWS; r++) {
      bool pressed = (digitalRead(ROWS[r]) == LOW);

      if (pressed != rawReading[r][c]) {
        rawReading[r][c]   = pressed;
        lastChangeMs[r][c] = millis();
      }

      if ((millis() - lastChangeMs[r][c]) >= DEBOUNCE_MS) {
        if (pressed != stableState[r][c]) {
          stableState[r][c] = pressed;

          // Only print if this slot has a wired button (non-empty label)
          if (BTN_LABEL[r][c][0] != '\0') {
            Serial.print(BTN_LABEL[r][c]);
            Serial.println(pressed ? F(" PRESSED") : F(" released"));
          }
        }
      }
    }

    digitalWrite(COLS[c], HIGH);
  }
}