root / trunk / code / lib / src / libdragonfly / analog.c @ 241
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/**
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* Copyright (c) 2007 Colony Project
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*
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* Permission is hereby granted, free of charge, to any person
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* obtaining a copy of this software and associated documentation
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* files (the "Software"), to deal in the Software without
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* restriction, including without limitation the rights to use,
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* copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following
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* conditions:
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*
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* The above copyright notice and this permission notice shall be
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* included in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
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* OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
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* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
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* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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* OTHER DEALINGS IN THE SOFTWARE.
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**/
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/**
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* @file analog.c
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* @brief Analog input and output
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*
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* Contains functions for manipulating the ADC on the Dragonfly board.
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*
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* @author Colony Project, CMU Robotics Club
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* code mostly taken from fwr analog file (author: Tom Lauwers)
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**/
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#include <util/delay.h> |
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#include <avr/interrupt.h> |
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#include "analog.h" |
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// Internal Function Prototypes
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void set_adc_mux(int which); |
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/**
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* @defgroup analog Analog
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* Functions for manipulation the ADC on the dragonfly board.
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* All definitions may be found in analog.h.
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*
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* @{
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**/
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/**
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* Initializes the ADC.
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* Call analog_init before reading from the analog ports.
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*
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* @see analog8, analog10
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**/
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void analog_init(void) |
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{ |
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// ADC Status Register A
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// Bit 7 - ADEN is set (enables analog)
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// Bit 6 - Start conversion bit is set (must be done once for free-running mode)
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// Bit 5 - Enable Auto Trigger (for free running mode)
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// Bit 4 - ADC interrupt flag, 0
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// Bit 3 - Enable ADC Interrupt (required to run free-running mode)
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// Bits 2-0 - Set to create a clock divisor of 128, to make ADC clock = 8,000,000/128
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ADCSRA |= 0xEF;
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// ADC Status Register B
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// Bit 7, 5-3 - Must be cleared
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// Bit 2:0 - Set mode, currently cleared for free running operation
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// Bit 6 - Analog comparator mode - cleared
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// ADCSRB = 0x00;
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// ADMUX register
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// Bit 7,6 - Set voltage reference to AVcc (0b01)
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// Bit 5 - Set ADLAR bit for left adjust to do simple 8-bit reads
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// Bit 4 - X
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// Bit 3:0 - Sets the current channel, set to ADC7 (the external mux)
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ADMUX = 0x67;
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// Set external mux lines to outputs
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DDRG |= 0x1C;
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set_adc_mux(0x07);
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} |
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/**
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* Reads an eight bit number from an analog port.
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* analog_init must be called before using this function.
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*
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* @param which the analog port to read from. One of
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* the constants AN0 - AN7.
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*
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* @return the eight bit input to the specified port
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*
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* @see analog_init, analog10
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**/
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unsigned int analog8(int which) |
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{ |
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if(which < EXT_MUX)
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ADMUX = 0x60 + which;
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else if(which == EXT_MUX) |
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return 0; |
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else
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{ |
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ADMUX = 0x60 + EXT_MUX;
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set_adc_mux(which - 8);
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_delay_ms(1);
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} |
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_delay_ms(1); // need at least 130 us between conversions |
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return ADCH;
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} |
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/**
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* Reads a ten bit number from the specified port.
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* analog_init must be called before using this function.
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*
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* @param which the analog port to read from. Typically
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* a constant, one of AN0 - AN7.
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*
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* @return the ten bit number input to the specified port
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*
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* @see analog_init, analog8
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**/
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unsigned int analog10(int which) |
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{ |
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unsigned int adc_h = 0; |
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unsigned int adc_l = 0; |
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if(which < EXT_MUX)
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ADMUX = 0x60 + which;
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else if(which == EXT_MUX) |
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return 0; |
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else
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{ |
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ADMUX = 0x60 + EXT_MUX;
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set_adc_mux(which - 8);
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_delay_ms(1);
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} |
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_delay_ms(1);
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adc_l = ADCL; /* highest 2 bits of ADCL -> least 2 bits of analog val */
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adc_h = ADCH; /* ADCH -> 8 highest bits of analog val */
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return (adc_h << 2) | (adc_l >> 6); |
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} |
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/**
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* Returns the current position of the wheel, as an integer
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* in the range 0 - 255.
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* analog_init must be called before using this function.
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*
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* @return the orientation of the wheel, as an integer in
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* the range 0 - 255.
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*
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* @see analog_init
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**/
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int wheel(void) |
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{ |
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return analog8(WHEEL_PORT);
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} |
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/**@}**/ //end defgroup |
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SIGNAL (SIG_ADC) |
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{ |
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// This is just here to catch ADC interrupts because ADC is free running.
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// No code needs to be in here.
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} |
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void set_adc_mux(int which) |
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{ |
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// FIX THIS IN NEXT REVISION
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// ADDR2 ADDR1 ADDR0
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// G2.G4.G3 set mux to port 0-7 via binary selection
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// math would be much cleaner if it was G4.G3.G2
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// mask so only proper bits are possible.
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PORTG = (PORTG & 0xE3) | ((which & 0x03) << 3) | (which & 0x04); |
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} |
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