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Topic: Non blocking PWM measurement issues. (Read 276 times) previous topic - next topic

vip1

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/*  rcTiming.ino -- JW, 30 November 2015 --
 * Uses pin-change interrupts on A0-A4 to time RC pulses
 *
 * Ref: http://arduino.stackexchange.com/questions/18183/read-rc-receiver-channels-using-interrupt-instead-of-pulsein
 *
 */
#include <Streaming.h>
static   byte rcOld;        // Prev. states of inputs
volatile unsigned long rcRises[4]; // times of prev. rising edges
volatile unsigned long rcTimes[4]; // recent pulse lengths
volatile unsigned int  rcChange=0; // Change-counter

// Be sure to call setup_rcTiming() from setup()
void setup_rcTiming() {
  rcOld = 0;
  pinMode(A0, INPUT);  // pin 14, A0, PC0, for pin-change interrupt
  pinMode(A1, INPUT);  // pin 15, A1, PC1, for pin-change interrupt
  pinMode(A2, INPUT);
  pinMode(A3, INPUT);
  PCMSK1 |= 0x0F;       // Four-bit mask for four channels
  PCIFR  |= 0x02;       // clear pin-change interrupts if any
  PCICR  |= 0x02;       // enable pin-change interrupts
}
// Define the service routine for PCI vector 1
ISR(PCINT1_vect) {
  byte rcNew = PINC & 15;   // Get low 4 bits, A0-A3
  byte changes = rcNew^rcOld;   // Notice changed bits
  byte channel = 0;
  unsigned long now = micros(); // micros() is ok in int routine
  while (changes) {
    if ((changes & 1)) {  // Did current channel change?
      if ((rcNew & (1<<channel))) { // Check rising edge
        rcRises[channel] = now;     // Is rising edge
      } else {              // Is falling edge
        rcTimes[channel] = now-rcRises[channel];
      }
    }
    changes >>= 1;      // shift out the done bit
    ++channel;
    ++rcChange;
  }
  rcOld = rcNew;        // Save new state
}

void setup() {
  Serial.begin(115200);
  Serial.println("Starting RC Timing Test");
  setup_rcTiming();
}

void loop() {
  unsigned long rcT[4]; // copy of recent pulse lengths
  unsigned int rcN;
  if (rcChange) {

    // Data is subject to races if interrupted, so off interrupts
    cli();          // Disable interrupts
    rcN = rcChange;
    rcChange = 0;       // Zero the change counter
    rcT[0] = rcTimes[0];
    rcT[1] = rcTimes[1];
    rcT[2] = rcTimes[2];
    rcT[3] = rcTimes[3];
    sei();          // reenable interrupts

    Serial << "t=" << millis() << " " << rcT[0] << " " << rcT[1]
       << " " << rcT[2] << " " << rcT[3] << " " << rcN << endl;
  }
  sei();            // reenable interrupts
}




source: https://arduino.stackexchange.com/questions/18183/read-rc-receiver-channels-using-interrupt-instead-of-pulsein/18221#18221

Arduino UNO R3 atmega328p

i am using this code in my project read pwm signal.Only one channel is needed so only pin A0 is used and rest are unused (A1-A3).The problem is that when there is no pwm signal it stores the previous value of pwm signal, while in project it needs to be go to zero when signal is not present.

secondly can i use pin 3 to read pwm.To do that what would be to change in above code?

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