Pour GreenRbot, j'ai renoncé à fabriquer tous mes capteurs à partir de composant récupérés. Mon premier achat a été 2 capteurs Sharp IR.

Vous trouverez ci-dessous le petit bout de logiciel qui m'a servi à valider le principe. Le logiciel est écrit pour le compilateur CCS.

J'ai fait le test en intérieur, reste à valider à l'extérieur si des variations d'ensoleillement n'influent pas trop sur les mesures.

*                               Pour affichage GP2YOA02 en cm
 
 ****************************************************************************/

#include <16f877.h>

#fuses HS,NOPROTECT,NOWDT,BROWNOUT,PUT,NOLVP

#ORG 0x1F00,0x1FFF {} /* Reserve memory for bootloader for the 8k 16F876/7 */

#device PIC16F877 *=16 /* Allow RAM to expand beyond 256 bytes */

#device adc=10 /* Make sure that we are sampling on 10 bits. This directive
                  is required for compiler version 2.7. */

/* Set the clock speed */
#use delay(clock=20000000)

/* Directive for RS-232 interface */
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7)

/* Definitions */

/* Analog channel definitions */
#define ADC_DELAY          20 /* Delay in microseconds */

#define DISTANCE_ANCH      4 /* Port A5/AN4 */

/* IR calibration data */
#define IR_DISTANCE_BASE   10
#define IR_DISTANCE_STEP   2
#define NUM_IR_CALIB_DATA  31

/* Type definitions */

typedef int uint8_t;

typedef long uint16_t;

/* Public interface */
void main(void);

void init_pins(void);
void init(void);

void display_ir_distance(void);

/* IR sensor interface */
uint8_t get_ir_distance(uint8_t ir_reading);
void monitor_ir_distance_sensor(void);

/* Variable definitions */
static const uint8_t ir_calib_data[NUM_IR_CALIB_DATA] = {
  124, 107, 93, 83, 75, 67, 62, 57, 53, 49, 47, 44, 42, 39, 38, 36,
   34,  33, 32, 30, 29, 28, 27, 26, 25, 25, 24, 23, 23, 22, 21
};

uint8_t distance = 0xff;

/*****************************************************************************
 * Init hardware pins: Set up the TRIS, set up analog ports, set the
 * pins to their default values.
 ****************************************************************************/
void
init_pins(void) {
  /* Set up the various pins in/out */
  set_tris_a(0b00100000); /* Pin A5 is input. Rest is not used. */
  set_tris_b(0b00000000); /* Port B is not used. */
  set_tris_c(0b10000000); /* C6 is output. C7 is input. Rest is not used. */
  set_tris_d(0b00000000); /* Port D is not used. */
  set_tris_e(0b00000000); /* Port E is not used. */
} /* init_pins */

/*****************************************************************************
 * Board initialization. Initialize pins.
 ****************************************************************************/
void
init(void) {
  init_pins();
} /* init */

/*****************************************************************************
 * This is the main control loop.
 ****************************************************************************/
void
main(void) {
  char c;

  init();

  printf("ADC Demornrn");

  for ( ; ; ) {
    printf("press key to get ADC value: ");
    for ( ; ; ) {
      if (kbhit())
        break;

      c = getc();

      printf("rn");

      monitor_ir_distance_sensor();
      display_ir_distance();
    }
  }
} /* main */

void
display_ir_distance(void) {
  printf("distance = %3u cm n", distance);
} /* display_status */

/* IR sensor implementation */

/*
 * get_ir_distance
 *
 * Determine distance in cm based in the A/D value and the calibration table.
 *
 * Parameters:
 * ir_reading (IN) - A/D value for the IR sensor
 */
uint8_t
get_ir_distance(uint8_t ir_reading) {
  int i;

  for (i = 0; i < NUM_IR_CALIB_DATA; i++) {
    if (ir_calib_data[i] < ir_reading) {
      return IR_DISTANCE_BASE + i * IR_DISTANCE_STEP;
    }
  }

  return IR_DISTANCE_BASE + (i - 1) * IR_DISTANCE_STEP;
} /* get_ir_distance */

/*****************************************************************************
 * This function monitors the IR distance sensor.
 * This function updates the distance global variable.
 ****************************************************************************/
void
monitor_ir_distance_sensor(void) {
  uint16_t value;

  /* Read ADC for left sensor */
  setup_adc_ports(A_ANALOG);
  setup_adc(ADC_CLOCK_DIV_8);

  set_adc_channel(DISTANCE_ANCH); /* Read Port A5/AN4 */

  delay_us(ADC_DELAY);
  value = Read_ADC();
  setup_adc(ADC_OFF);

  value >>= 2;

  distance = get_ir_distance(value);
} /* monitor_ir_distance_sensor */