RPM/Speed display w Hall Effect Sensor & Throttle ramping fix

README.md

@@ -42,7 +42,6 @@ The next iteration of Kilobyte introduces many structural and user interface imp
     - [x] Create new Arduino shield for power and all IO
   - [ ] Upgrade & enhance firmware
     - [ ] Show battery voltage and percentage on screen
-	- [ ] Implement master software shutoff switch
     - [x] Make UI more user friendly
     - [x] Add safeguards for when communication to control unit is lost
     - [x] Implement UI LEDs
@@ -53,8 +52,8 @@ The next iteration of Kilobyte introduces many structural and user interface imp
   - [x] Finalize mounting of all electronics and batteries
     - [x] Test mounting for strength and neatness
   - [x] Ensure all electronics are properly fused
-  - [ ] Neatly route power+communication wiring to display unit
-    - [ ] Design custom cable harness/mounting atachments
+  - [x] Neatly route power+communication wiring to display unit
+    - [x] Design custom cable harness/mounting atachments
   - [x] Cut a wooden board to mount electronics on
     - [x] Design battery mounting solution
 - Cosmetics
@@ -70,7 +69,7 @@ The next iteration of Kilobyte introduces many structural and user interface imp
 - Safety
   - [ ] Detect human presence on chariot, do not allow operation if not detector
   - [ ] Add configurable speed limiter
-  - [ ] Add a hardware battery disconnect
+  - [x] Add a hardware battery disconnect
   - [ ] Grip tape / bed liner for chariot
 - Cosmetics
   - [ ] clean and clear coat aluminum 

firmware/control.ino

@@ -3,6 +3,7 @@
 // -------------------- Pin Definitions --------------------
 #define PWM   9
 #define PWM2  10
+#define HALL_SENSOR A0
 
 // -------------------- I2C Variables --------------------
 byte receivedThrottle = 180; 
@@ -19,6 +20,20 @@ const float accelStep = 4.0;     // how much each button press adds
 const float decayStep = 1.5;     // how fast it returns to neutral
 const float minThrottle = 180;
 
+// -------------------- Hall Effect Sensor --------------------
+const int hallEffectLow = 500;     // baseline should stay below this
+const int hallEffectHigh = 650;    // magnet pass should be above this
+const float wheelDiameter = 24.13;   // wheel diameter in centimeters (9.5inch = 24.13cm)
+const uint8_t magnetsPerRevolution = 1;
+const unsigned long rpmTimeout = 2000; // threshold in ms to consider rpm 0
+
+volatile uint16_t rpmToSend = 0;
+
+bool pulseArmed = true;
+unsigned long lastPulseMicros = 0;
+unsigned long lastPulseMillis = 0;
+float currentRpm = 0.0;
+
 // -------------------- I2C Receive ----------------------
 void receiveEvent(int numBytes) {
   if (numBytes >= 3) {
@@ -30,6 +45,12 @@ void receiveEvent(int numBytes) {
   }
 }
 
+// -------------------- I2C Request --------------------
+void requestEvent() {
+  uint16_t rpm = rpmToSend;
+  Wire.write((uint8_t)(rpm & 0xFF));
+  Wire.write((uint8_t)(rpm >> 8));
+}
 
 // -------------------- Accelerate With Button Press --------------------
 void updateThrottle() {
@@ -56,14 +77,49 @@ void updateThrottle() {
   }
 }
 
+// -------------------- Hall Sensor RPM --------------------
+void updateRpm() {
+  int hallEffectRaw = analogRead(HALL_SENSOR);
+  unsigned long nowMicros = micros();
+  unsigned long nowMillis = millis();
+
+  if (pulseArmed && hallEffectRaw >= hallEffectHigh) {
+    if (lastPulseMicros != 0) {
+      unsigned long periodMicros = nowMicros - lastPulseMicros;
+      if (periodMicros > 0) {
+        currentRpm = 60000000.0 /* 1 minute in microseconds */ / (periodMicros * magnetsPerRevolution);
+      }
+    }
+
+    lastPulseMicros = nowMicros;
+    lastPulseMillis = nowMillis;
+    pulseArmed = false;
+  } else if (!pulseArmed && hallEffectRaw <= hallEffectLow) {
+    pulseArmed = true;
+  }
+
+  if (lastPulseMillis == 0 || (nowMillis - lastPulseMillis) > rpmTimeout) {
+    currentRpm = 0.0;
+  }
+
+  if (currentRpm < 0) currentRpm = 0; // prevent negative RPM
+  if (currentRpm > 65535) currentRpm = 65535; // prevent overflow
+
+  noInterrupts(); // ensure variable doesn't change in the middle of setting it
+  rpmToSend = (uint16_t)(currentRpm + 0.5); // round to nearest integer
+  interrupts();
+}
+
 // -------------------- Setup --------------------
 void setup() {
   Serial.begin(9600);
   Wire.begin(8);  
   Wire.onReceive(receiveEvent);
+  Wire.onRequest(requestEvent);
 
   pinMode(PWM, OUTPUT);
   pinMode(PWM2, OUTPUT);
+  pinMode(HALL_SENSOR, INPUT);
 }
 
 // -------------------- Main Loop --------------------
@@ -81,18 +137,31 @@ void loop() {
 
   // Update throttle based on buttons
   updateThrottle();
+  updateRpm();
+
+  uint8_t pwmRight = (uint8_t)constrain((int)(rightThrottle + 0.5f), 0, 255);
+  uint8_t pwmLeft  = (uint8_t)constrain((int)(leftThrottle  + 0.5f), 0, 255);
+
+  analogWrite(PWM,  pwmRight);
+  analogWrite(PWM2, pwmLeft);
+
+  // Speed (km/h) derived from wheel diameter and current RPM, kept here for tuning.
+  float wheelCircumference = (wheelDiameter / 100.0) * 3.14159265; // in meters
+  float speed = (currentRpm * wheelCircumference * 60.0) / 1000.0; // in km/h
 
-  // Apply throttle to both motors unless one button disables it
-  analogWrite(PWM,  (receivedRight == 0 ? receivedThrottle : 180));
-  analogWrite(PWM2, (receivedLeft  == 0 ? receivedThrottle : 180));
+// Debugging output
 
+//   Serial.print("Left: ");
+//   Serial.print(receivedThrottle);
+//   Serial.print(receivedLeft);
+//   Serial.print("  Right: ");
+//   Serial.println(receivedThrottle);
+//   Serial.print(receivedRight);
 
-  Serial.print("Left: ");
-  Serial.print(receivedThrottle);
-  Serial.print(receivedLeft);
-  Serial.print("  Right: ");
-  Serial.println(receivedThrottle);
-  Serial.print(receivedRight);
+//   Serial.print("RPM: ");
+//   Serial.print((uint16_t)currentRpm);
+//   Serial.print("  Speed(km/h): ");
+//   Serial.println(speed, 2);
 
   delay(10);
 }

firmware/display.ino

@@ -11,12 +11,18 @@
 #define LEFT 6
 #define RIGHT 7
 
+const uint8_t CONTROL_I2C_ADDRESS = 0x08;
+
 // -------------------- LCD --------------------
 LiquidCrystal_I2C lcd(0x27, 20, 4);
 
 unsigned long lastLcdUpdate = 0;
 const unsigned long lcdUpdateInterval = 100;
 
+unsigned long lastRpmPoll = 0;
+const unsigned long rpmPollInterval = 100;
+uint16_t currentRpm = 0;
+
 // -------------------- Reverse Beeper --------------------
 unsigned long lastBeepTime = 0;
 const unsigned long beepInterval = 1600;
@@ -28,6 +34,8 @@ const unsigned long beepDuration = 800;
 const float smoothFactor = 0.10;
 float smoothedThrottle = 0;
 
+const float wheelDiameter = 24.13;   // wheel diameter in centimeters (9.5inch = 24.13cm)
+
 float smooth(float previous, float current) {
   return previous + smoothFactor * (current - previous);
 }
@@ -60,6 +68,15 @@ void drawThrottleBar(int throttlePercent, int totalBlocks) {
   lcd.print("]");
 }
 
+void requestRpm() {
+  Wire.requestFrom((int)CONTROL_I2C_ADDRESS, 2);
+  if (Wire.available() >= 2) {
+    uint8_t low = Wire.read();
+    uint8_t high = Wire.read();
+    currentRpm = (uint16_t)(low | ((uint16_t)high << 8));
+  }
+}
+
 void update_lcd(bool reverseActive) {
   int throttlePercent = map(smoothedThrottle, 1023, 0, 0, 100);
 
@@ -70,15 +87,21 @@ void update_lcd(bool reverseActive) {
     lcd.print("FWD ");
     drawThrottleBar(throttlePercent, 10);  // high-res bar
     lcd.print(" ");                        // padding
+    lcd.print(throttlePercent);
+    lcd.print("%");
   }
 
-  lcd.print(throttlePercent);
-  lcd.print("%");
+  float wheelCircumference = (wheelDiameter / 100.0) * 3.14159265;
+  float speedKmh = (currentRpm * wheelCircumference * 60.0) / 1000.0;
 
   // placeholder, will be speedometer
   lcd.setCursor(0, 3);
-  drawThrottleBar(throttlePercent, 18);
-
+  lcd.print("RPM:");
+  lcd.print(currentRpm);
+  lcd.print(" SPD:");
+  lcd.print(speedKmh, 1);
+  lcd.print("km/h ");
+}
 
   // -------------------- Reverse Beep --------------------
 void handleReverseBeep(bool reverseActive) {
@@ -100,6 +123,7 @@ void handleReverseBeep(bool reverseActive) {
   }
 }
 
+// -------------------- Startup Song --------------------
 void play_startup_song() {
   // Imperial March melody
   int melody[] = {
@@ -138,13 +162,21 @@ void play_startup_song() {
   delay(70);
 }
 
+// -------------------- I2C Packet --------------------
+bool sendPacket(byte throttle, byte leftBtn, byte rightBtn) {
+  Wire.beginTransmission(CONTROL_I2C_ADDRESS);
+  Wire.write(throttle);
+  Wire.write(leftBtn);
+  Wire.write(rightBtn);
+  byte status = Wire.endTransmission();
+  return (status == 0);
+}
 
   // -------------------- Setup --------------------
 void setup() {
   Wire.begin();
-
   lcd.init();
-  lcd.createChar(0, block0);
+
   lcd.createChar(1, block1);
   lcd.createChar(2, block2);
   lcd.createChar(3, block3);
@@ -158,8 +190,6 @@ void setup() {
 
   pinMode(LED, OUTPUT);
   pinMode(LED2, OUTPUT);
-  pinMode(PWM, OUTPUT);
-  pinMode(PWM2, OUTPUT);
   pinMode(BUZZER, OUTPUT);
 
   digitalWrite(LED, HIGH);
@@ -174,43 +204,33 @@ void setup() {
   Serial.begin(9600);
 }
 
-  // -------------------- I2C Packet --------------------
-  bool sendPacket(byte throttle, byte leftBtn, byte rightBtn) {
-    Wire.beginTransmission(8);
-    Wire.write(throttle);
-    Wire.write(leftBtn);
-    Wire.write(rightBtn);
-
-    byte status = Wire.endTransmission();
-    return (status == 0);
-  }
-
   // -------------------- Main Loop --------------------
 void loop() {
   unsigned long now = millis();
 
   smoothedThrottle = smooth(smoothedThrottle, analogRead(THROTTLE));
   bool reverseActive = !digitalRead(REVERSE);
-  int leftPressed = digitalRead(LEFT);
-  int rightPressed = digitalRead(RIGHT);
+  byte leftPressed = digitalRead(LEFT);
+  byte rightPressed = digitalRead(RIGHT);
 
   // Throttle mapping
   //  180 = zero throttle
   //  255 = full
-  //  0 = full rever
-  int driveThrottle = map(smoothedThrottle, 1023, 0, 180, 255);
+  //  0 = full reverse
+  int driveThrottle = map((int)smoothedThrottle, 1023, 0, 180, 255);
 
   if (reverseActive) {
     driveThrottle = 255 - driveThrottle;
   }
 
-  // Send packet to control unit
-  while (!sendPacket(driveThrottle, leftPressed, rightPressed)) {
-    left = 0;
-    right = 0;  // disable input
-    lcd.clear();
-    lcd.print("COMMUNICATION LOST");
-    delay(1000);
+  if (!sendPacket((byte)driveThrottle, leftPressed, rightPressed)) {
+    lcd.setCursor(0, 1);
+    lcd.print("COMMUNICATION LOST   ");
+  } else {
+    if (now - lastRpmPoll >= rpmPollInterval) {
+      requestRpm();
+      lastRpmPoll = now;
+    }
   }
 
   handleReverseBeep(reverseActive);