The Arduino is coded up and it seems to be working!

Here's the Arduino code - pretty simple.

(sorry, I don't know how to display code all fancy-like at the moment!)

#include "LedControl.h"
#include "NewPing.h"

/* ---------------> Sonar Stuff <--------------- */
#define triggerPin  12
#define echoPin     10
#define maxDistance 400
NewPing sonar(triggerPin,echoPin,maxDistance);

/* ---------------> LED Stuff <--------------- */
#define Din         7
#define CLK         8
#define CS          9
LedControl lc = LedControl(Din,CLK,CS,1);

/* ---------------> speaker Stuff <--------------- */
#define speakerPin  11

#define triggerDistance 100 // cm
int i = 0;

void setup() 
{
  Serial.begin(115200);

  // LEDs
  lc.shutdown(false,0);
  lc.setIntensity(0,8);
  lc.clearDisplay(0);
  for (i=0;i<=3;i++)
  {
    lc.setChar(0,i,i,false);
    delay(100);
    lc.setChar(0,i,' ',false);
  }
  for (i=3;i>=0;i--)
  {
    lc.setChar(0,i,i,false);
    delay(100);
    lc.setChar(0,i,' ',false);
  }

pinMode(speakerPin, OUTPUT);

}

void loop() 
{
  delay(50);
  int uS = sonar.ping();
  int distance = 0;
  int toneDelay = 0;
  
  distance = uS / US_ROUNDTRIP_CM;
  printDistanceOnLED(distance);
  toneDelay = distance * 4;


  if (triggerDistance > distance)
  {
    playTone(toneDelay,500);
    delay(toneDelay);
    playTone(toneDelay,500);
    delay(toneDelay);
  }
}

void printDistanceOnLED(int distance)
{
  int metres = 0;
  int cms = 0;
  int cms_tens = 0;
  int cms_ones = 0;

  metres = distance / 100;
  distance = distance - metres * 100;
  cms_tens = distance / 10;
  cms_ones = distance % 10;

  // only display digits if non-zero
  if (0 != metres)
  {lc.setDigit(0,1,(byte)metres,false);}
  else
  {lc.setDigit(0,1,' ',false);}
  
  if ((0 != cms_tens) || (0 != metres))
  {lc.setDigit(0,2,(byte)cms_tens,false);}
  else
  {lc.setDigit(0,2,' ',false);}
  
  if ((0 != cms_ones) || ((0 != cms_tens) || (0 != metres)))
  {lc.setDigit(0,3,(byte)cms_ones,false);}
  else
  {lc.setDigit(0,3,' ',false);}
  
  lc.setDigit(0,0,' ',true);
  
  Serial.print(metres); Serial.print("."); Serial.print(cms_tens); Serial.print(cms_ones); Serial.println("m");
}

// duration in mSecs, frequency in hertz
// http://michael.thegrebs.com/2009/03/23/playing-a-tone-through-an-arduino-connected-piezo/
void playTone(long duration, int freq) {
    duration *= 1000;
    int period = (1.0 / freq) * 1000000;
    long elapsed_time = 0;
    while (elapsed_time < duration) {
        digitalWrite(speakerPin,HIGH);
        delayMicroseconds(period / 2);
        digitalWrite(speakerPin, LOW);
        delayMicroseconds(period / 2);
        elapsed_time += (period);
    }
}

Tags: arduino, sonar, bicyle