Linearizing Code for Sharp GP2D120 Infrared Ranger

This program takes input from a Sharp GP2D120 infrared ranging sensor and outputs the result in ASCII. The ranging formula comes from an excellent article on Acroname’s site, tweaked a bit to work with my circuit.

Written in Wiring syntax, tested on an Arduino board:

/*
 GP2D120 sensor example
 by Tom Igoe 
 
  Reads a changing voltage from a GP2D120 IR ranging sensor
  on analog input 0 and sends the result out in ASCII-encoded
  decimal numbers.
   
 Arduino/ATMega8 hardware connections:
 A0/PC5: potentiometer on analog in 1
 D0/PD0/RX0: Serial input from the PC via MAX232 or hex inverter
 D1/PD1/TX0: Serial output to PC via MAX232 or hex inverter
 
 Distance ranging formula comes from Acroname, http://www.acroname.com:
 http://www.acroname.com/robotics/info/articles/irlinear/irlinear.html
 
 Created 6 Oct. 2005 
 Updated 25 Oct. 2005
 */

int val;             // outgoing ADC value
int distance = 0;

//function prototype:
void blink(int howManyTimes);

void setup()
{
  // start serial port at 9600 bps:
  beginSerial(9600);
  blink(3);
}

void loop()
{
  // read analog input:
  val = analogRead(0); 
  // send analog value out:
  printString("Analog Value =\t");
  // Calculate linear slope of reading (thanks, Acroname!):
  distance = (2914 / (val + 5)) - 1;
  printInteger(distance);
  printString("\n\r");
  // wait 10ms for ADC to reset before next reading:
  delay(10);                 
}


// Blink the reset LED:
void blink(int howManyTimes) {
  int i;
  for (i=0; i< howManyTimes; i++) {
    digitalWrite(13, HIGH);
    delay(200);
    digitalWrite(13, LOW);
    delay(200);  
  }
}

Written for the BX-24:


 'GP2D120 sensor example
 'by Tom Igoe 
 
 ' Reads a changing voltage from a GP2D120 IR ranging sensor
 ' on analog input 0 and sends the result out in ASCII-encoded
 ' decimal numbers.

 ' Analog in is on pin 15 of the BX-24
   
' Distance ranging formula comes from Acroname, http://www.acroname.com:
' http://www.acroname.com/robotics/info/articles/irlinear/irlinear.html

 
' created 6 Oct 2005
' Updated 25 Oct. 2005
 

dim val as integer             '  outgoing ADC value
dim distance as integer

sub main ()
    call blink(3)
do
'  read analog input:
  val = getADC(15)
   '  Calculate linear slope of reading (thanks, Acroname!):
  distance = (2914 / (val + 5)) - 1
 '  send analog value out:
  debug.print "Distance = "; cStr(distance)
  '  wait 10ms for ADC to reset before next reading:
  call delay(0.01)                 
loop
end sub


'  Blink the reset LED:
sub blink(byVal howManyTimes as integer) 
  dim i as integer
  for i=0 to howManyTimes 
    call putPin(26, 1)
    call delay(0.2)
    call putPin(26,0)
    call delay(0.2)  
  next
end sub

Written in PicBasic Pro, tested on a PIC18F252:


' GP2D120 sensor example
' by Tom Igoe 
 
'  Reads a changing voltage from a GP2D120 IR ranging sensor
'  on analog input 0 and sends the result out in ASCII-encoded
'  decimal numbers.
   
' Distance ranging formula comes from Acroname, http://www.acroname.com:
' http://www.acroname.com/robotics/info/articles/irlinear/irlinear.html
' I had to change the final constant to match my sensor's readings.
 
' Created 6 Oct. 2005 
' Updated 25 Oct. 2005
 
 ' Define ADCIN parameters
DEFINE  ADC_BITS        10     ' Set number of bits in result
DEFINE  ADC_CLOCK       3         ' Set clock source (3=rc)
DEFINE  ADC_SAMPLEUS    50        ' Set sampling time in uS

' pins: 
tx var portc.6          ' serial TX
rx var portc.7          ' serial RX
resetLED var portb.7    ' blinking LED
' analog in is on porta.0

' constant to set the baud rate:
inv9600 con 16468

' define variables:
adcVar var word
distance var word

' subroutine variables:
i var byte

TRISA = %11111111       ' Set PORTA to all input
ADCON1 = %10000010      ' Set PORTA analog and right justify result

setup:
  gosub blink

main:
  '  read analog input:
  adcin 0, adcVar
  '  Calculate linear slope of reading (thanks, Acroname!):
  distance = (2914 / (adcVar + 5)) - 1
  ' send the distance out:
  serout2 tx, inv9600, ["Distance = ", 9, distance, 10, 13]
  '  wait 10ms for ADC to reset before next reading:
  pause 10                 
goto main


'  Blink the reset LED:
blink:
  for i=0 to 3 
   high resetLED
   pause 200
   low resetLED
   pause 200
  next
return

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