00001 /*! \file a2d.c \brief Analog-to-Digital converter function library. */ 00002 //***************************************************************************** 00003 // 00004 // File Name : 'a2d.c' 00005 // Title : Analog-to-digital converter functions 00006 // Author : Pascal Stang - Copyright (C) 2002 00007 // Created : 2002-04-08 00008 // Revised : 2002-09-30 00009 // Version : 1.1 00010 // Target MCU : Atmel AVR series 00011 // Editor Tabs : 4 00012 // 00013 // This code is distributed under the GNU Public License 00014 // which can be found at http://www.gnu.org/licenses/gpl.txt 00015 // 00016 //***************************************************************************** 00017 00018 #include <avr/io.h> 00019 #include <avr/signal.h> 00020 #include <avr/interrupt.h> 00021 00022 #include "global.h" 00023 #include "a2d.h" 00024 00025 // global variables 00026 00027 //! Software flag used to indicate when 00028 /// the a2d conversion is complete. 00029 volatile unsigned char a2dCompleteFlag; 00030 00031 // functions 00032 00033 // initialize a2d converter 00034 void a2dInit(void) 00035 { 00036 sbi(ADCSR, ADEN); // enable ADC (turn on ADC power) 00037 cbi(ADCSR, ADFR); // default to single sample convert mode 00038 a2dSetPrescaler(ADC_PRESCALE); // set default prescaler 00039 a2dSetReference(ADC_REFERENCE); // set default reference 00040 cbi(ADMUX, ADLAR); // set to right-adjusted result 00041 00042 sbi(ADCSR, ADIE); // enable ADC interrupts 00043 00044 a2dCompleteFlag = FALSE; // clear conversion complete flag 00045 sei(); // turn on interrupts (if not already on) 00046 } 00047 00048 // turn off a2d converter 00049 void a2dOff(void) 00050 { 00051 cbi(ADCSR, ADIE); // disable ADC interrupts 00052 cbi(ADCSR, ADEN); // disable ADC (turn off ADC power) 00053 } 00054 00055 // configure A2D converter clock division (prescaling) 00056 void a2dSetPrescaler(unsigned char prescale) 00057 { 00058 outb(ADCSR, ((inb(ADCSR) & ~ADC_PRESCALE_MASK) | prescale)); 00059 } 00060 00061 // configure A2D converter voltage reference 00062 void a2dSetReference(unsigned char ref) 00063 { 00064 outb(ADMUX, ((inb(ADMUX) & ~ADC_REFERENCE_MASK) | (ref<<6))); 00065 } 00066 00067 // sets the a2d input channel 00068 void a2dSetChannel(unsigned char ch) 00069 { 00070 outb(ADMUX, (inb(ADMUX) & ~ADC_MUX_MASK) | (ch & ADC_MUX_MASK)); // set channel 00071 } 00072 00073 // start a conversion on the current a2d input channel 00074 void a2dStartConvert(void) 00075 { 00076 sbi(ADCSR, ADIF); // clear hardware "conversion complete" flag 00077 sbi(ADCSR, ADSC); // start conversion 00078 } 00079 00080 // return TRUE if conversion is complete 00081 u08 a2dIsComplete(void) 00082 { 00083 return bit_is_set(ADCSR, ADSC); 00084 } 00085 00086 // Perform a 10-bit conversion 00087 // starts conversion, waits until conversion is done, and returns result 00088 unsigned short a2dConvert10bit(unsigned char ch) 00089 { 00090 a2dCompleteFlag = FALSE; // clear conversion complete flag 00091 outb(ADMUX, (inb(ADMUX) & ~ADC_MUX_MASK) | (ch & ADC_MUX_MASK)); // set channel 00092 sbi(ADCSR, ADIF); // clear hardware "conversion complete" flag 00093 sbi(ADCSR, ADSC); // start conversion 00094 //while(!a2dCompleteFlag); // wait until conversion complete 00095 //while( bit_is_clear(ADCSR, ADIF) ); // wait until conversion complete 00096 while( bit_is_set(ADCSR, ADSC) ); // wait until conversion complete 00097 00098 // CAUTION: MUST READ ADCL BEFORE ADCH!!! 00099 return (inb(ADCL) | (inb(ADCH)<<8)); // read ADC (full 10 bits); 00100 } 00101 00102 // Perform a 8-bit conversion. 00103 // starts conversion, waits until conversion is done, and returns result 00104 unsigned char a2dConvert8bit(unsigned char ch) 00105 { 00106 // do 10-bit conversion and return highest 8 bits 00107 return a2dConvert10bit(ch)>>2; // return ADC MSB byte 00108 } 00109 00110 //! Interrupt handler for ADC complete interrupt. 00111 SIGNAL(SIG_ADC) 00112 { 00113 // set the a2d conversion flag to indicate "complete" 00114 a2dCompleteFlag = TRUE; 00115 } 00116