asynch (non-blocking) ultrasonic sensors for adruino due

async_ultrasonic.c

#include <DueTimer.h>

#define trigPin1 13                                    // Pin 12 trigger output
#define trigPin2 11                                    // Pin 12 trigger output
#define trigPin3 9                                    // Pin 12 trigger output

#define echoPin1 12                                    // Pin 2 Echo input
#define echoPin2 10                                    // Pin 2 Echo input
#define echoPin3 8                                    // Pin 2 Echo input

volatile long echo_start1 = 0;                         // Records start of echo pulse 
volatile long echo_end1 = 0;                           // Records end of echo pulse
volatile long echo_duration1 = 0;                      // Duration - difference between end and start
volatile long echo_start2 = 0;                         // Records start of echo pulse 
volatile long echo_end2 = 0;                           // Records end of echo pulse
volatile long echo_duration2 = 0;                      // Duration - difference between end and start
volatile long echo_start3 = 0;                         // Records start of echo pulse 
volatile long echo_end3 = 0;                           // Records end of echo pulse
volatile long echo_duration3 = 0;                      // Duration - difference between end and start

// ----------------------------------
// setup() routine called first.
// A one time routine executed at power up or reset time.
// Used to initialise hardware.
// ----------------------------------
void setup() 
{
  pinMode(trigPin1, OUTPUT);                           // Trigger pin set to output
  pinMode(trigPin2, OUTPUT);
  pinMode(trigPin3, OUTPUT);
  pinMode(echoPin1, INPUT);    
  pinMode(echoPin2, INPUT); 
  pinMode(echoPin3, INPUT); // Echo pin set to input
  Timer6.attachInterrupt(trigger_pulse).start(250000);     //sends a pulse every 250 ms and lasts 50 us
 
  attachInterrupt(echoPin1, echo_interrupt1, CHANGE);  // Attach interrupt to the sensor echo input
  attachInterrupt(echoPin2, echo_interrupt2, CHANGE);  // Attach interrupt to the sensor echo input
  attachInterrupt(echoPin3, echo_interrupt3, CHANGE);  // Attach interrupt to the sensor echo input
  Serial.begin (9600);                                // Initialise the serial monitor output
}

// ----------------------------------
// loop() Runs continuously in a loop.
// This is the background routine where most of the processing usualy takes place.
// Non time critical tasks should be run from here.
// ----------------------------------
void loop()
{
    Serial.print("S1= ");Serial.print(echo_duration1 / 58);               // Print the distance in centimeters
    Serial.print(" S2= ");Serial.print(echo_duration2 / 58);               // Print the distance in centimeters
    Serial.print(" S3= ");Serial.println(echo_duration3 / 58);               // Print the distance in centimeters
    
    delay(10);                                       // every 100 mS
}

void trigger_pulse()
{
     //sets all pins to high or triggers the ultrasonic
     digitalWrite(trigPin1, HIGH);
     digitalWrite(trigPin2, HIGH);
     digitalWrite(trigPin3, HIGH);
     Timer7.attachInterrupt(goLow).start(50);     //sets a  timer that will make the pulse go low after 50 us
     
}

void goLow()
{
  //sets all the pins to low
  //Serial.println("pin goes low");
  digitalWrite(trigPin1, LOW);
  digitalWrite(trigPin2, LOW);
  digitalWrite(trigPin3, LOW);
  Timer7.detachInterrupt();                        //detachs the interupt so that it won't go off again until initialized
  
}

void echo_interrupt1()                          
{
  switch (digitalRead(echoPin1))                     // Test to see if the signal is high or low
  {
    case HIGH:                                      // High so must be the start of the echo pulse
      echo_end1 = 0;                                 // Clear the end time
      echo_start1 = micros();                        // Save the start time
      break;
      
    case LOW:                                       // Low so must be the end of the echo pulse
      echo_end1 = micros();                          // Save the end time
      echo_duration1 = echo_end1 - echo_start1;        // Calculate the pulse duration
      break;
  }
}

void echo_interrupt2()
{
  switch (digitalRead(echoPin2))                     // Test to see if the signal is high or low
  {
    case HIGH:                                      // High so must be the start of the echo pulse
      echo_end2 = 0;                                 // Clear the end time
      echo_start2 = micros();                        // Save the start time
      break;
      
    case LOW:                                       // Low so must be the end of hte echo pulse
      echo_end2 = micros();                          // Save the end time
      echo_duration2 = echo_end2 - echo_start2;        // Calculate the pulse duration
      break;
  }
}

void echo_interrupt3()
{
  switch (digitalRead(echoPin3))                     // Test to see if the signal is high or low
  {
    case HIGH:                                      // High so must be the start of the echo pulse
      echo_end3 = 0;                                 // Clear the end time
      echo_start3 = micros();                        // Save the start time
      break;
      
    case LOW:                                       // Low so must be the end of hte echo pulse
      echo_end3 = micros();                          // Save the end time
      echo_duration3 = echo_end3 - echo_start3;        // Calculate the pulse duration
      break;
  }
}