128 lines
3.9 KiB
C++
128 lines
3.9 KiB
C++
/*
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* File: varDutyT1.ino
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* Purpose: Varying the duty-cycle of the PWM on output pins 9 and 10 via the analog A0 input. Update rate: 15.625kHz, resolution: 10-bits.
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*
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* Version: 1.0.0
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*
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* By: M. Stokroos
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*
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* Date: 02-12-2019
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*
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*/
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// Library to be included for fast digital I/O when observing the timing with an oscilloscope.
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//#include <digitalWriteFast.h> // library for high performance digital reads and writes by jrraines
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// see http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1267553811/0
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// and http://code.google.com/p/digitalwritefast/
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#define LPERIOD 500000 // the main loop period time in us. In this case 500ms.
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#define PIN_LED 13 // PLL locking status indicator LED
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#define PIN_PWMA 9 // Timer1 OCR1A 10-bit PWM
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#define PIN_PWMB 10 // Timer1 OCR1B 10-bit PWM
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#define PIN_DEBUG 4 // test output pin
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// global vars
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volatile int adcVal;
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unsigned long nextLoop;
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// ******************************************************************
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// Setup
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// ******************************************************************
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void setup(){
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cli(); // disable interrupts
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pinMode(PIN_LED, OUTPUT);
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pinMode(PIN_PWMA, OUTPUT);
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pinMode(PIN_PWMB, OUTPUT);
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pinMode(PIN_DEBUG, OUTPUT);
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// initialize ADC for continuous sampling mode
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DIDR0 = 0x3F; // digital inputs disabled for ADC0D to ADC5D
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bitSet(ADMUX, REFS0); // Select Vcc=5V as the ADC reference voltage
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bitClear(ADMUX, REFS1);
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bitClear(ADMUX, MUX0); // selecting ADC CH# 0
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bitClear(ADMUX, MUX1);
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bitClear(ADMUX, MUX2);
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bitClear(ADMUX, MUX3);
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bitSet(ADCSRA, ADEN); // AD-converter enabled
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bitSet(ADCSRA, ADATE); // auto-trigger enabled
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bitSet(ADCSRA, ADIE); // ADC interrupt enabled
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bitSet(ADCSRA, ADPS0); // ADC clock prescaler set to 128
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bitSet(ADCSRA, ADPS1);
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bitSet(ADCSRA, ADPS2);
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bitClear(ADCSRB, ACME); // Analog Comparator (ADC)Multiplexer enable OFF
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bitClear(ADCSRB, ADTS0); // triggered by Timer/Counter1 Overflow
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bitSet(ADCSRB, ADTS1);
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bitSet(ADCSRB, ADTS2);
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bitSet(ADCSRA, ADSC); // start conversion
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/* configuring TIMER1 for PWM-mode 7 */
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// prescaler = 1:
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bitSet(TCCR1B, CS10);
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bitClear(TCCR1B, CS11);
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bitClear(TCCR1B, CS12);
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// mode 7:
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bitSet(TCCR1A, WGM10);
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bitSet(TCCR1A, WGM11);
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bitSet(TCCR1B, WGM12);
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bitClear(TCCR1B, WGM13);
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//set output compare
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bitClear(TCCR1A, COM1A0); // Compare Match PWM 9
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bitSet(TCCR1A, COM1A1);
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bitSet(TCCR1A, COM1B0); // Compare Match PWM 10 - inverted channel
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bitSet(TCCR1A, COM1B1);
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// enable TIMER1 compare interrupt
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bitSet(TIMSK1, TOIE1); // enable Timer1 Interrupt
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sei(); // global enable interrupts
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nextLoop = micros() + LPERIOD; // Set the loop timer variable for the next loop interval.
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}
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// ******************************************************************
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// Main loop
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// ******************************************************************
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void loop(){
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// do nothing here except for flashing the LED...
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digitalWrite(PIN_LED, !digitalRead(PIN_LED));
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while(nextLoop > micros()); // wait until the end of the time interval
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nextLoop += LPERIOD; // set next loop time at current time + LOOP_PERIOD
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}
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/* ******************************************************************
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* ADC ISR. The ADC is triggered by Timer1.
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* *******************************************************************/
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ISR(ADC_vect){
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//digitalWriteFast(PIN_DEBUG, HIGH); //for checking the interrupt frequency
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// read the current ADC input channel
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adcVal=ADCL; // store low byte
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adcVal+=ADCH<<8; // store high byte
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// write out 10bit PWM output registers A&B (pin9 and pin10).
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OCR1AH = adcVal>>8; //MSB
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OCR1AL = adcVal; //LSB
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//(inverted) output:
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OCR1BH = OCR1AH; //MSB
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OCR1BL = OCR1AL; //LSB
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//digitalWriteFast(PIN_DEBUG, LOW);
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}
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/* ******************************************************************
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* Timer1 ISR
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*********************************************************************/
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ISR(TIMER1_OVF_vect) {
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//empty ISR. Only used to trigger the ADC.
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}
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