Keyboard: Handle key presses once, debounce (untested)

firmware/src/constants.h

@@ -24,3 +24,6 @@
 // --- Keyboard config
 
 #define KBD_I2C_ADDR 0x21
+
+// Used by keyboard and encoder switch
+#define DEBOUNCE_MS 10

firmware/src/encoder.cpp

@@ -13,8 +13,6 @@ When rotated clockwise, CLK changes before DT; when rotated counter-clockwise, D
 
 */
 
-#define SW_DEBOUNCE_MS 10
-
 bool previousClk = false;
 bool previousDt = false;
 
@@ -40,8 +38,8 @@ SwitchEvent handleSwitch() {
   }
 
   // debounce
-  unsigned long now = millis();
-  if (now - lastChangeAt < SW_DEBOUNCE_MS) {
+  auto now = millis();
+  if (now - lastChangeAt < DEBOUNCE_MS) {
     return SWITCH_NONE;
   }
 

firmware/src/keyboard.cpp

@@ -3,6 +3,7 @@
 
 #include "constants.h"
 #include "debug.h"
+#include "keyboard.h"
 
 PCF8574 kbd(KBD_I2C_ADDR, &Wire);
 
@@ -15,15 +16,10 @@ row/col 0 1 2 3
   1     4 5 6 B
   2     7 8 9 C
   3     * 0 # D
-
-  Keys, in order:
-  123A 456B 789C *0#D
 */
 
-typedef uint8_t Key;
-
 const char *allKeys = "123A456B789C*0#D";
-#define KEY_NONE 255
+
 const uint8_t digits[16] =
   { 1, 2, 3, KEY_NONE,
     4, 5, 6, KEY_NONE,
@@ -43,30 +39,35 @@ bool setupKeyboard() {
   return true;
 }
 
+Key previousKey = KEY_NONE;
+unsigned long lastPressedAt = 0;
+
 Key getPressedKey();
-uint8_t getPressedDigit(Key key);
+Key handleKeyboard() {
+  auto key = getPressedKey();
+
+  // only handle change
+  if (key == previousKey) {
+    return KEY_NONE;
+  }
+
+  // debounce
+  auto now = millis();
+  if (now - lastPressedAt < DEBOUNCE_MS) {
+    return KEY_NONE;
+  }
+
+  // save state
+  previousKey = key;
+  lastPressedAt = now;
+
+  // return event
+  return key;
+}
 
 #define KBD_COL_MASK 0b11110000
 #define KBD_ROW_MASK 0b00001111
 
-void demoKeyboard() {
-  auto key = getPressedKey();
-  if (key != KEY_NONE) {
-    Serial.print("Key pressed: ");
-    Serial.print(allKeys[key]);
-
-    auto digit = getPressedDigit(key);
-    if (digit != KEY_NONE) {
-      Serial.print(", digit: ");
-      Serial.print(digit);
-    } else {
-      Serial.print(" (Not a digit)");
-    }
-
-    Serial.println();
-  }
-}
-
 /**
  * Returns pressed key or KEY_NONE if no key is pressed
  *
@@ -107,9 +108,6 @@ Key getPressedKey() {
   return (rowPressed * 4) + colPressed;
 }
 
-/**
- * Returns pressed digit or KEY_NONE if the key is not a digit
- */
 uint8_t getPressedDigit(Key key) {
   if (key == KEY_NONE) return KEY_NONE;
   return digits[key];

firmware/src/keyboard.h

@@ -1,4 +1,26 @@
 #pragma once
 
+/*
+  Keys, in order:
+  123A 456B 789C *0#D
+ */
+typedef uint8_t Key;
+#define KEY_NONE 255
+
+extern const char *allKeys;
+
 bool setupKeyboard();
-void demoKeyboard();
+
+/**
+ * Returns pressed key once upon its release
+ * or KEY_NONE if no key is pressed
+ *
+ * NOTE: Only one key can be pressed at a time;
+ * if multiple keys are pressed, the behavior is undefined
+ */
+Key handleKeyboard();
+
+/**
+ * Returns pressed digit or KEY_NONE if the key is not a digit
+ */
+uint8_t getPressedDigit(Key key);

firmware/src/main.cpp

@@ -26,7 +26,23 @@ void loop() {
 
   // debugScanI2C();
   // demoScreen();
-  // demoKeyboard();
+
+  auto key = handleKeyboard();
+  if (key != KEY_NONE) {
+    tick();
+    Serial.print("Key pressed: ");
+    Serial.print(allKeys[key]);
+
+    auto digit = getPressedDigit(key);
+    if (digit != KEY_NONE) {
+      Serial.print(", digit: ");
+      Serial.print(digit);
+    } else {
+      Serial.print(" (Not a digit)");
+    }
+
+    Serial.println();
+  }
 
   if (auto event = handleSwitch()) {
     tick();