Allows for separate angles with Intake and Exhaust plus removed the print statements from the interrupt callback.

ArduinoHallEffect/ArduinoHallEffect.ino

@@ -0,0 +1,70 @@
+// An Arduino program for controlling valve timing on a 6.5ph Predator engine from Harbor Freight.
+//
+// Wesley Kagan, 2020
+// Ric Allinson, 2020
+
+// Control variables.
+const int DEG_PER_MAGNET = 6;       // Number of degrees for each magnet.
+const int FREEVALVE_OFFSET_TOP = 0; // The amount of off set from TDC (needs to be multiples of DEG_PER_MAGNET).
+const int FREEVALVE_OFFSET_BOTTOM = 180 + FREEVALVE_OFFSET_TOP; 
+
+// Pins assignment.
+const int HALL_MAGNET = 2;
+const int EXHAUST_V = 12;
+const int INTAKE_V = 13;
+
+int cad;                   // Crank Angle Degrees (CAD).
+int hallCounter;           // The number of magnets after the last TDC.
+bool cycle;                // "true" for Intake, "false" for Exhaust.
+bool printLog;             // Used to trigger a print in the loop.
+unsigned long timeGap;     // Function level time between interrupts.
+unsigned long lastTimeGap; // Global level time between interrupts.
+
+void setup() {
+  Serial.begin(115200);
+  pinMode(HALL_MAGNET, INPUT);
+  attachInterrupt(0, magnetDetect, RISING);
+  pinMode(INTAKE_V, OUTPUT);
+  pinMode(EXHAUST_V, OUTPUT);
+}
+
+void loop() {
+  if(printLog){
+    Serial.print(lastTimeGap);
+    Serial.print(cycle);
+    Serial.print(cad);
+    printLog = false;
+  }
+}
+
+// This function will be called about every 15.79ms at the maximum RPM of 3800.
+void magnetDetect() {
+  // Increment the counter to keep track of the position.
+  hallCounter++;
+  // Get the time gap between this interrupt and the last.
+  timeGap = millis() - lastTimeGap;
+
+  // Find missing tooth for Top Dead Center (TDC).
+  if (timeGap >= lastTimeGap * 3 / 2) {
+    // Reset the hall counter.
+    hallCounter = 1;
+    // Flip the cycle phase.
+    cycle = !cycle;
+  }
+
+  // Store the last time difference so we can use it in the next interrupt.
+  lastTimeGap = timeGap;
+
+  // Store the current crank angle for logging.
+  cad = hallCounter * DEG_PER_MAGNET;
+
+  // Every rotation of the crank alternates between Intake and Exhaust.
+  if (cycle) {
+    // If the crank angle degree is in the intake range open it, otherwise close it.
+    digitalWrite(INTAKE_V, cad > FREEVALVE_OFFSET_TOP && cad <= FREEVALVE_OFFSET_BOTTOM);
+  } else {
+    // If the crank angle degree is in the exhaust range open it, otherwise close it.
+    digitalWrite(EXHAUST_V, cad >= FREEVALVE_OFFSET_BOTTOM || cad < FREEVALVE_OFFSET_TOP);
+  }
+  printLog = true;
+}