Raspberry Pi / Digispark distance measurement 1.

I used the following sketch to be able to receive the distance measurement from an HC-SR04 ultrasound sensor connected to the Digispark on the Pi using the digispark example 'receive.py' script.

#include <DigiUSB.h>

//

// AJR - 17/4/13.  USing HC-SR04 to measure distance

// and output on the USB so it can be read on an RPi.

// Use with the receive python progs 

// from the Digispark examples.

// DigisparkExamplePrograms-master.

//

#define trigPin 0

#define echoPin 2

char data[] = "The quick brown fog jumped over the lazy dogx";

long distance = 42;

long duration;

void setup() {

  DigiUSB.begin();

  pinMode(1,OUTPUT); //give us some idea it's workng by flashing led

  pinMode(trigPin, OUTPUT);

  pinMode(echoPin, INPUT);

}

void measure() {

  int lastRead;

  while (true) { // loop forever

    digitalWrite(1,HIGH);

    DigiUSB.delay(100);

    // Try measure, and send response.

    digitalWrite(trigPin, LOW);  // Trig needs to go high on 10us pulse

    delayMicroseconds(2); // wait....

    digitalWrite(trigPin, HIGH);

    delayMicroseconds(10); // Trig pin pulse time.

    digitalWrite(trigPin, LOW);  // Now, we time to echo.

    duration = pulseIn(echoPin, HIGH);

    distance = (duration/2) / 29.1;

    ltoa(distance, data, 10);

    strcat(data, " cm");

    DigiUSB.println(data);

    digitalWrite(1,LOW);

    delay(500); //sleep for 0.5 seconds before sending again.

  }

}

void loop() {

  // print output

  DigiUSB.println("Waiting for input...");

  digitalWrite(1, LOW); 

  // Measure....

  measure();

}