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 <util/delay.h>

#include <avr/interrupt.h>

#include "analog.h"

// Internal Function Prototypes

void set_adc_mux(int which);

/**

 * @defgroup analog Analog

 * Functions for manipulation the ADC on the dragonfly board.

 * All definitions may be found in analog.h.

 *

 * @{

 **/

/**

 * Initializes the ADC.

 * Call analog_init before reading from the analog ports.

 *

 * @see analog8, analog10

 **/

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 4 - ADC interrupt flag, 0

        // 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 = 8,000,000/128

        ADCSRA |= 0xEF;

        // ADC Status Register B

        // Bit 7, 5-3 - Must be cleared

        // Bit 2:0 - Set mode, currently cleared for free running operation

        // Bit 6 - Analog comparator mode - cleared

//        ADCSRB = 0x00;

        // 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, set to ADC7 (the external mux)

        ADMUX = 0x67;

        // Set external mux lines to outputs

        DDRG |= 0x1C;

        set_adc_mux(0x07);

}        

/**

 * Reads an eight bit number from an analog port.

 * analog_init must be called before using this function.

 * 

 * @param which the analog port to read from. One of

 * the constants AN0 - AN7.

 *

 * @return the eight bit input to the specified port

 *

 * @see analog_init, analog10

 **/

unsigned int analog8(int which)

{

        if(which < EXT_MUX)

                ADMUX = 0x60 + which;

        else if(which == EXT_MUX)

                return 0;

        else

        {

                ADMUX = 0x60 + EXT_MUX;

                set_adc_mux(which - 8);

                _delay_ms(1);

        }

        _delay_ms(1); // need at least 130 us between conversions

        return ADCH;

}

/**

 * Reads a ten bit number from the specified port.

 * analog_init must be called before using this function.

 *

 * @param which the analog port to read from. Typically

 * a constant, one of AN0 - AN7.

 *

 * @return the ten bit number input to the specified port

 * 

 * @see analog_init, analog8

 **/

unsigned int analog10(int which)

{

        unsigned int adc_h = 0;

        unsigned int adc_l = 0;

        if(which < EXT_MUX)

                ADMUX = 0x60 + which;

        else if(which == EXT_MUX)

                return 0;

        else

        {

                ADMUX = 0x60 + EXT_MUX;

                set_adc_mux(which - 8);

                _delay_ms(1);

        }

        _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);

}

/**

 * Returns the current position of the wheel, as an integer

 * in the range 0 - 255.

 * analog_init must be called before using this function.

 *

 * @return the orientation of the wheel, as an integer in

 * the range 0 - 255.

 *

 * @see analog_init

 **/

int wheel(void)

{

        return analog8(WHEEL_PORT);

}

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

SIGNAL (SIG_ADC)

{

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

        // No code needs to be in here.

}

void set_adc_mux(int which)

{

  // FIX THIS IN NEXT REVISION

  // ADDR2 ADDR1 ADDR0

  // G2.G4.G3 set mux to port 0-7 via binary selection

  // math would be much cleaner if it was G4.G3.G2

  // mask so only proper bits are possible.  

  PORTG = (PORTG & 0xE3) | ((which & 0x03) << 3) | (which & 0x04);

}