Fast PWM mode

HVTestFastPWM/HVTestFastPWM.ino

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+//**********************************************************************************
+//**********************************************************************************
+//*  Fire up HV generator for testing                                              *
+//*  Uses a feedback loop via the analogue in to make sure that we produce more or *
+//*  less constantly 200V, regardless of the input voltage.                        *
+//*  We achieve this by turning off the HV generator if the voltage we measure     *
+//*  is above the required voltage, otherwise we turn it on.                       *
+//**********************************************************************************
+//**********************************************************************************
+
+#include <avr/io.h>
+
+//**********************************************************************************
+//**********************************************************************************
+//*                                     Variables                                  *
+//**********************************************************************************
+//**********************************************************************************
+const int PWM_TOP_DEFAULT = 1000;
+const int PWM_TOP_MIN = 200;
+const int PWM_TOP_MAX = 10000;
+int pwmTop = PWM_TOP_DEFAULT;
+
+// pin used to drive the DC-DC converter
+int hvDriverPin = 9;
+int tickLed = 13;
+int sensorPin = A0;    // select the input pin for the potentiometer
+
+// precalculated values for turning on and off the HV generator
+// Put these in TCCR1B to turn off and on
+int tccrOff;
+int tccrOn;
+
+
+//**********************************************************************************
+//**********************************************************************************
+//*                                                          Setup                                                                *
+//**********************************************************************************
+//**********************************************************************************
+void setup() 
+{
+  pinMode(tickLed, OUTPUT);
+
+  // Set the driver pin to output
+  pinMode(9, OUTPUT);
+
+  TCCR1A = 0;    // disable all PWM on Timer1 whilst we set it up
+  TCCR1B = 0;    // disable all PWM on Timer1 whilst we set it up
+  ICR1 = pwmTop; // Our starting point for the period	
+
+  // Configure timer 1 for Fast PWM mode via ICR1, with prescaling=1
+  TCCR1A = (1 << WGM11);
+  TCCR1B = (1 << WGM13) | (1<<WGM12) | (1 << CS10);
+
+  tccrOff = TCCR1A;
+
+  TCCR1A |= (1 <<  COM1A1);  // enable PWM on port PD4 in non-inverted compare mode 2
+
+  tccrOn = TCCR1A;
+
+  OCR1A = 150;  // Pulse width of the on time
+}
+
+//**********************************************************************************
+//**********************************************************************************
+//*                                                       Main loop                                                             *
+//**********************************************************************************
+//**********************************************************************************
+void loop()     
+{
+  int rawSensorVal = analogRead(sensorPin);  
+  double sensorVoltage = rawSensorVal * 5.0  / 1024.0;
+  double externalVoltage = sensorVoltage * 394.7 / 4.7;
+  //Serial.println(externalVoltage);
+
+  if (externalVoltage > 180) {
+    pwmTop++;
+    if (pwmTop > PWM_TOP_MAX) {
+      pwmTop = PWM_TOP_MAX;
+    }
+    ICR1 = pwmTop; // Our starting point for the period	
+    digitalWrite(tickLed,0);
+  } 
+  else {
+    pwmTop--;
+    if (pwmTop < PWM_TOP_MIN) {
+      pwmTop = PWM_TOP_MIN;
+    }
+    ICR1 = pwmTop; // Our starting point for the period	
+    digitalWrite(tickLed,1);
+  }
+}
+
+
+
+