Colony

/*

Authors: James Kong and Greg Tress

Last Modified: 4/30/06 by James

-Started log_distance conversion function !!!NOT COMPLETE!!!

-Cleaning up comments

-----------------

rangefinder.c

Using Sharp GP2D02 IR Rangefinder

Vin is the input to the rangefinder, designated RANGE_CTRL.

Vout is the output from the rangefinder, designated RANGE_IN# where # is the rangefinder you are reading from

Expected Initial Conditions:

Vin is high and Vout should read high.

Usage:

1.) Set Vin low. Vout should read low.

2.) Wait for high on Vout.

3.) Begin clocking Vin and reading 8 bits from Vout (MSB first).

4.) Set Vin high for 2ms or more to turn off rangefinder

*/

#include "dragonfly_lib.h"

#include "rangefinder.h"

/*

read_distance returns the 8-bit reading from the rangefinder

parameters:

range_id - dio pin set as the rangefinder Vout [i.e. RANGE_IN0]

NOTE:

The Sharp GD2D02 returns values on a decreasing logrithmic scale.

So higher values correspond to closer distances.  Use linearize_distance to convert to normal centimeter scale.

Also, when reading distances closer than 8cm, the Sharp GD2D02 will return lower values than the values at 8cm.

At this point, we are only reading from one rangefinder [RANGE_IN0].

*/

// constants

/* Nasty IR approximation table

  I'm using this for the heck of it.  We can do whatever.

  Note the minimum value is .4V (20), and the maximum is 2.6V (133).

  Gives distance in mm.

  excel formula(valid for inputs 20-133):  ROUND(2353.6*(E2^(-1.1146))*10,0)

  This is only valid for the GP2D12, with objects directly ahead and more than

  10cm from the detector.  See the datasheet for more information.

*/

#define MIN_IR_ADC8 20

#define MAX_IR_ADC8 133

static int IR_dist_conversion[114] = {

800,791,751,714,681,651,623,597,574,552,531,512,494,478,462,447

,434,421,408,397,386,375,365,356,347,338,330,322,315,307,301,294

,288,282,276,270,265,260,255,250,245,241,237,232,228,224,221,217

,213,210,207,203,200,197,194,191,189,186,183,181,178,176,173,171

,169,166,164,162,160,158,156,154,152,151,149,147,145,144,142,140

,139,137,136,134,133,131,130,129,127,126,125,124,122,121,120,119

,118,117,115,114,113,112,111,110,109,108,107,106,105,105,104,103

,102,101

};

int linearize_distance(int value);

/**

 * @defgroup rangefinder Rangefinder

 * @brief Functions for using the IR rangefinders

 * 

 * Functions for using the IR rangefinders.

 *

 * @{

 **/

/**

 * Initializes the rangefinders. This must be called before

 * range_read_distance.

 *

 * @see range_read_distance

 **/

void range_init(void){

  digital_output(_PIN_B4,0);

}

/**

 * Reads the distance measured by one of the rangefinders.

 * This distance is in arbitrary units.

 *

 * @param range_id the rangefinder to use. This should be one

 * of the constants IR1 - IR5.

 *

 * @return the distance measured by the rangefinder

 *

 * @see range_init

 **/

int range_read_distance (int range_id) {  

  return linearize_distance(analog8(range_id));

}

/** @} **/ //end defgroup

int linearize_distance(int value)

{

  if(value < MIN_IR_ADC8)

  {

    return -1;

  }

  else if(value > MAX_IR_ADC8)

  {

    return -1;

  }

  else

  {

    return IR_dist_conversion[value - MIN_IR_ADC8];

  }

}