Arduino core pulsein() issues and attach interrupt questions

Development Boards Artemis
1

I am using the pulsein() function in a sketch to read the distance from a Maxbotix ultrasonic sensor pulse width output (<100ms). I have never had an issue with any of the Arduino boards I have used but on the RedBoard Artemis the pulsein() often, but not always, times out yielding a 0 output. Can you suggest why this is happening and how to work around the problem?

Also, I have tried another approach to reading that output based on interrupts but have not been able to figure out how to attach an interrupt to any of the PWM pins as silkscreen labeled on the RedBoard.

2

Hi, I am not familiar with pulseIn() so I will be of little use there, unfortunately. However I can help with the interrupts. You should be able to attach an interrupt to any pin by simply using the pin number (which is in silkscreen - the extra symbols like A, ~, etc… don’t matter) in code like this:

/* Author: Owen Lyke
 Created: June 19 2019
 License: MIT. See SparkFun Arduino Apollo3 Project for more information

 This example demonstrates usage of Arduino interrupts.
 All interrupt modes are enabled, however HIGH and LOW are software controlled because the Apollo3 does not
 support HIGH or LOW interrupt states in hardware. 

When HIGH or LOW is selected as an interrupt mode the pad value is read during each ISR call and if the value
no longer matches the mode the ISR flag is cleared. Keep in mind that as long as the interrupt condition
remains true only registered ISRs will execute (in order of first attachment for each pin)

The edge-based interrupts will clear the flag automatically.

*/

#define INT_PIN 16
static uint32_t count = 0;
bool interruptsEnabled = false;

void setup()
{
  // put your setup code here, to run once:

  Serial.begin(9600);
  Serial.println("Interrupt testing");

  pinMode(INT_PIN, INPUT_PULLUP);

  attachInterrupt(digitalPinToInterrupt(INT_PIN), myISR, RISING);
  //  attachInterrupt(digitalPinToInterrupt(INT_PIN), myISR, FALLING);
  //  attachInterrupt(digitalPinToInterrupt(INT_PIN), myISR, LOW);
  //  attachInterrupt(digitalPinToInterrupt(INT_PIN), myISR, HIGH);
  //  attachInterrupt(digitalPinToInterrupt(INT_PIN), myISR, CHANGE);

  //  // attaching a different interrupt to the same pin overwrites the existing ISR
  //  attachInterruptArg(digitalPinToInterrupt(INT_PIN), myISRArg, &count, RISING);

  interruptsEnabled = true;
}

void loop()
{
  count++;
  if (count > 5)
  {
    if (interruptsEnabled)
    {
      detachInterrupt(digitalPinToInterrupt(INT_PIN));
      interruptsEnabled = false;
    }
  }
  delay(1000);
}

void myISR(void)
{
  Serial.println("Hi i am an ISR!");
}

void myISRArg(void *arg)
{
  uint32_t *local_count = (uint32_t *)arg;
  Serial.printf("The time is %d seconds\n", *(local_count));
}

P.s. this example is under Sketch->Examples->Artemis Examples->Example_attachInterrupts