bumper.c

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/*
 * control module for Bumper sensors
 * (c) 2007 by Matthias Arndt <matthias.arndt@tu-clausthal.de>
 *
 */
#include "t89c51cc02.h"
#include "datatypes.h"
#include "bumper.h"
#include "adc.h"

void Bumper_init()
{
        P2=(P2 & 0xFC); /* clear msb of bumper control bus */
        P1_5=0; /* clear lsb of bumper control bus */

        Bumper_deactivate();    /* make sure bumper sensors are not active */

        ADCF |= 0x08;   /* enable analogue input on P1.3 for bumpers */
}

void Bumper_select(BYTE sensorid)
{

        sensorid=(sensorid & 0x07); /* mask sensors which are not allowed */

        P2=(P2 & 0xFC)|(sensorid & 0x03); /* set lower bus bits */      
        P1_5=(bit) (sensorid & 0x04); /* set lsb of decoder bus */

        /* trade in some time to latch the new address properly */
        _asm
        nop
        nop
        nop
        _endasm;
}

WORD Bumper_read(BYTE bumpernr)
{
        WORD result;

        /* the subsystem assumes that the bumpers are turned on and off only when required */
        Bumper_select(bumpernr);
        Bumper_activate();
        result=ADC(3);  /* read bumper value from P1.3 (bumper analogue input) */
        Bumper_deactivate();
        return(result);
}

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