Colony

/*

        analog.c - Contains the function implementations for manipulating the ADC

        on the firefly+ board

        author:  CMU Robotics Club, Colony Project

        code mostly taken from fwr analog file (author: Tom Lauwers)

*/

#include <avr/delay.h>

#include <avr/interrupt.h>

#include <avr/signal.h>

#include "analog.h"

void analog_init(void){

        /*

                ADC Status Register A

                Bit 7 - ADEN is set (enables analog)

                Bit 6 - Start conversion bit is set (must be done once for free-running mode)

                Bit 5 - Enable Auto Trigger (for free running mode)

                Bit 3 - Enable ADC Interrupt (required to run free-running mode)

                Bits 2-0 - Set to create a clock divisor of 128, to make ADC clock = 16,000,000/128

        */

        ADCSRA |= 0xEF;

        /*

                ADMUX register

                Bit 7,6 - Set voltage reference to AVcc (0b01)

                Bit 5 - Set ADLAR bit for left adjust to do simple 8-bit reads

                Bit 4 - X

                Bit 3:0 - Sets the current channel

        */

        ADMUX = 0x67;

}        

unsigned int analog8(int which){

        ADMUX = 0x60 + which;

        _delay_ms(1); // need at least 130 us between conversions (for fwr robot, how much for new avr?)

        return ADCH;

}

unsigned int analog10(int which){

        unsigned int adc_h = 0;

        unsigned int adc_l = 0;

        ADMUX = 0x60 + which;

        _delay_ms(1);

        adc_l = ADCL; /* highest 2 bits of ADCL -> least 2 bits of analog val */

        adc_h = ADCH; /* ADCH -> 8 highest bits of analog val */

        return (adc_h << 2) | (adc_l >> 6);

}

int wheel(void){

        return analog8(WHEEL_PORT);

}

int battery(void){

        return analog8(BATT_PORT) * 500 / 255; /* 5 volts is the max, 255 is the max 8bit number */

}

SIGNAL (SIG_ADC)

{

        // This is just here to catch ADC interrupts because ADC is free running.  

        // No code needs to be in here.

}