Xmega Application Note


adc_driver.c File Reference


Detailed Description

XMEGA ADC driver source file.

This file contains the function implementations the XMEGA ADC driver.

The driver is not intended for size and/or speed critical code, since most functions are just a few lines of code, and the function call overhead would decrease code performance. The driver is intended for rapid prototyping and documentation purposes for getting started with the XMEGA ADC module.

For size and/or speed critical code, it is recommended to copy the function contents directly into your application instead of making a function call.

Several functions use the following construct: "some_register = ... | (some_parameter ? SOME_BIT_bm : 0) | ..." Although the use of the ternary operator ( if ? then : else ) is discouraged, in some occasions the operator makes it possible to write pretty clean and neat code. In this driver, the construct is used to set or not set a configuration bit based on a boolean input parameter, such as the "some_parameter" in the example above.

Application note:
AVR1300: Using the XMEGA ADC
Documentation
For comprehensive code documentation, supported compilers, compiler settings and supported devices see readme.html
Author:
Atmel Corporation: http://www.atmel.com
Support email: avr@atmel.com
Revision
Date

Copyright (c) 2008, Atmel Corporation All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

3. The name of ATMEL may not be used to endorse or promote products derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY ATMEL "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE EXPRESSLY AND SPECIFICALLY DISCLAIMED. IN NO EVENT SHALL ATMEL BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Definition in file adc_driver.c.

#include "adc_driver.h"

Include dependency graph for adc_driver.c:

Go to the source code of this file.

Functions

void ADC_CalibrationValues_Load (ADC_t *adc)
 This function get the calibration data from the production calibration.
int8_t ADC_Offset_Get_Signed (ADC_t *adc, ADC_CH_t *ch, bool oversampling)
 This function gets the offset of the ADC when it is configured in signed mode.
uint8_t ADC_Offset_Get_Unsigned (ADC_t *adc, ADC_CH_t *ch, bool oversampling)
 This function gets the offset of the ADC when it is configured in unsigned mode.
uint8_t ADC_ResultCh_GetHighByte (ADC_CH_t *adc_ch)
 This function clears the interrupt flag and returns the high byte of the coversion result.
uint8_t ADC_ResultCh_GetLowByte (ADC_CH_t *adc_ch)
 This function clears the interrupt flag and returns the low byte of the coversion result.
uint16_t ADC_ResultCh_GetWord (ADC_CH_t *adc_ch)
 This function clears the interrupt flag and returns the coversion result without compensating for offset.
int16_t ADC_ResultCh_GetWord_Signed (ADC_CH_t *adc_ch, int8_t signedOffset)
 This function clears the interrupt flag and returns the signed coversion result.
uint16_t ADC_ResultCh_GetWord_Unsigned (ADC_CH_t *adc_ch, uint8_t offset)
 This function clears the interrupt flag and returns the unsigned coversion result.
void ADC_Wait_32MHz (ADC_t *adc)
 This function waits until the adc common mode is settled.
void ADC_Wait_8MHz (ADC_t *adc)
 This function waits until the adc common mode is settled.


Function Documentation

void ADC_CalibrationValues_Load ( ADC_t *  adc  ) 

This function get the calibration data from the production calibration.

The calibration data is loaded from flash and stored in the calibration register. The calibration data reduces the non-linearity error in the adc.

Parameters:
adc Pointer to ADC module register section.

Definition at line 77 of file adc_driver.c.

Referenced by main().

00078 {
00079         if(&ADCA == adc){
00080                  /* Get ADCACAL0 from production signature . */
00081                 adc->CALL = SP_ReadCalibrationByte( PROD_SIGNATURES_START + ADCACAL0_offset );
00082                 adc->CALH = SP_ReadCalibrationByte( PROD_SIGNATURES_START + ADCACAL1_offset );
00083         }else {
00084                 /* Get ADCBCAL0 from production signature  */
00085                 adc->CALL = SP_ReadCalibrationByte( PROD_SIGNATURES_START + ADCBCAL0_offset );
00086                 adc->CALH = SP_ReadCalibrationByte( PROD_SIGNATURES_START + ADCACAL1_offset );
00087         }
00088 }

int8_t ADC_Offset_Get_Signed ( ADC_t *  adc,
ADC_CH_t *  ch,
bool  oversampling 
)

This function gets the offset of the ADC when it is configured in signed mode.

This function does one or several measurements to determine the offset of the ADC.

Note:
The ADC must be configured and enabled before this function is run.

This function only return the low byte of the 12-bit convertion, because the offset should never be more than +-8 LSB off.

Parameters:
adc Pointer to the ADC to calculate offset from.
ch Pointer to the ADC channel to measure on.
oversampling false for one measurement. true for averaging several measurements.
Returns:
Offset on the selected ADC

Definition at line 318 of file adc_driver.c.

Referenced by main().

00319 {
00320     if (oversampling)
00321     {
00322       int16_t offset=0;
00323       for (int i=0; i<4; i++)
00324       {
00325         /* Do one conversion to find offset. */
00326         ADC_Ch_Conversion_Start(ch);
00327     
00328         do{
00329         }while(!ADC_Ch_Conversion_Complete(ch));
00330         offset += ADC_ResultCh_GetWord_Signed(ch, 0x00);
00331       }
00332       return ((int8_t)(offset/4));
00333     }
00334     else
00335     {        
00336       int8_t offset=0;
00337       
00338       /* Do one conversion to find offset. */
00339       ADC_Ch_Conversion_Start(ch);
00340   
00341       do{
00342       }while(!ADC_Ch_Conversion_Complete(ch));
00343       offset = (uint8_t)ADC_ResultCh_GetWord_Signed(ch, 0x00);
00344       
00345       return offset;
00346     }
00347 }

uint8_t ADC_Offset_Get_Unsigned ( ADC_t *  adc,
ADC_CH_t *  ch,
bool  oversampling 
)

This function gets the offset of the ADC when it is configured in unsigned mode.

This function does one or several measurements to determine the offset of the ADC.

Note:
The ADC must be configured and enabled before this function is run.

This function only return the low byte of the 12-bit convertion, because the offset should never be more than +-8 LSB off.

Parameters:
adc Pointer to the ADC to calculate offset from.
ch Pointer to the ADC channel to measure on.
oversampling false for one measurement. true for averaging several measurements.
Returns:
Offset on the selected ADC

Definition at line 271 of file adc_driver.c.

00272 {
00273     if (oversampling)
00274     {
00275       uint16_t offset=0;
00276       for (int i=0; i<4; i++)
00277       {
00278         /* Do one conversion to find offset. */
00279         ADC_Ch_Conversion_Start(ch);
00280     
00281         do{
00282         }while(!ADC_Ch_Conversion_Complete(ch));
00283         offset += ADC_ResultCh_GetWord_Unsigned(ch, 0x00);
00284       }
00285       return ((uint8_t)(offset>>2));
00286     }
00287     else
00288     {        
00289       uint8_t offset=0;
00290       
00291       /* Do one conversion to find offset. */
00292       ADC_Ch_Conversion_Start(ch);
00293   
00294       do{
00295       }while(!ADC_Ch_Conversion_Complete(ch));
00296       offset = (uint8_t)ADC_ResultCh_GetWord(ch);
00297       
00298       return offset;
00299     }
00300 }

uint8_t ADC_ResultCh_GetHighByte ( ADC_CH_t *  adc_ch  ) 

This function clears the interrupt flag and returns the high byte of the coversion result.

This funtion should be used together with the ADC_ResultCh_ConversionComplete. When the conversion result is ready this function reads out the result.

Note:
If this function is used with 12-bit right adjusted results, it returns the 8 LSB only. Offset is not compensated.
Parameters:
adc_ch Pointer to ADC channel register section.
Returns:
High byte of conversion result.

Definition at line 186 of file adc_driver.c.

00187 {
00188         /* Clear interrupt flag.*/
00189         adc_ch->INTFLAGS = ADC_CH_CHIF_bm;
00190 
00191         /* Return low byte result register contents.*/
00192         return adc_ch->RESH;
00193 }

uint8_t ADC_ResultCh_GetLowByte ( ADC_CH_t *  adc_ch  ) 

This function clears the interrupt flag and returns the low byte of the coversion result.

This funtion should be used together with the ADC_Ch_Conversion_Complete. When the conversion result is ready this funciton reads out the result.

Note:
If this function is used with 12-bit right adjusted results, it returns the 8 LSB only. Offset is not compensated.
Parameters:
adc_ch Pointer to ADC channel register section.
Returns:
Low byte of conversion result.

Definition at line 166 of file adc_driver.c.

00167 {
00168         /* Clear interrupt flag.*/
00169         adc_ch->INTFLAGS = ADC_CH_CHIF_bm;
00170         /* Return result register contents*/
00171         return adc_ch->RESL;
00172 }

uint16_t ADC_ResultCh_GetWord ( ADC_CH_t *  adc_ch  ) 

This function clears the interrupt flag and returns the coversion result without compensating for offset.

This function should be used together with the ADC_Ch_Conversion_Complete. When the conversion result is ready this funciton reads out the result.

Parameters:
adc_ch Pointer to ADC channel register section.
Returns:
Signed conversion result.

Definition at line 144 of file adc_driver.c.

Referenced by ADC_Offset_Get_Unsigned().

00145 {
00146         /* Clear interrupt flag.*/
00147         adc_ch->INTFLAGS = ADC_CH_CHIF_bm;
00148 
00149         /* Return result register contents*/
00150         return adc_ch->RES;;
00151 }

int16_t ADC_ResultCh_GetWord_Signed ( ADC_CH_t *  adc_ch,
int8_t  signedOffset 
)

This function clears the interrupt flag and returns the signed coversion result.

This function should be used together with the ADC_Ch_Conversion_Complete. When the conversion result is ready this funciton reads out the result.

Parameters:
adc_ch Pointer to ADC channel register section.
signedOffset Offset value to subtract.
Returns:
The signed Conversion result with the offset substracted.

Definition at line 123 of file adc_driver.c.

Referenced by ADC_Offset_Get_Signed(), ISR(), and main().

00124 {
00125         int16_t answer;
00126 
00127         /* Clear interrupt flag.*/
00128         adc_ch->INTFLAGS = ADC_CH_CHIF_bm;
00129 
00130         /* Return result register contents*/
00131         answer = adc_ch->RES - signedOffset;
00132 
00133         return answer;
00134 }

uint16_t ADC_ResultCh_GetWord_Unsigned ( ADC_CH_t *  adc_ch,
uint8_t  offset 
)

This function clears the interrupt flag and returns the unsigned coversion result.

This function should be used together with the ADC_Ch_Conversion_Complete. When the conversion result is ready this funciton reads out the result.

Parameters:
adc_ch Pointer to ADC channel register section.
offset Unsigned offset value to subtract.
Returns:
The unsigned Conversion result with the offset substracted.

Definition at line 100 of file adc_driver.c.

Referenced by ADC_Offset_Get_Unsigned().

00101 {
00102         uint16_t answer;
00103 
00104         /* Clear interrupt flag.*/
00105         adc_ch->INTFLAGS = ADC_CH_CHIF_bm;
00106 
00107         /* Return result register contents*/
00108         answer = adc_ch->RES - offset;
00109 
00110         return answer;
00111 }

void ADC_Wait_32MHz ( ADC_t *  adc  ) 

This function waits until the adc common mode is settled.

After the ADC clock has been turned on, the common mode voltage in the ADC need some time to settle. The time it takes equals one dummy conversion. Instead of doing a dummy conversion this function waits until the common mode is settled.

Note:
The function sets the prescaler to the minimum value possible when the clock speed is larger than 8 MHz to minimize the time it takes the common mode to settle.

The ADC clock is turned off every time the ADC i disabled or the device goes into sleep (not Idle sleep mode).

Parameters:
adc Pointer to ADC module register section.

Definition at line 240 of file adc_driver.c.

00241 {
00242         /* Store old prescaler value. */
00243         uint8_t prescaler_val = adc->PRESCALER;
00244 
00245         /* Set prescaler value to minimum value. */
00246         adc->PRESCALER = ADC_PRESCALER_DIV8_gc;
00247 
00248         /* wait 8*COMMON_MODE_CYCLES for common mode to settle*/
00249         delay_us(8*COMMON_MODE_CYCLES);
00250 
00251         /* Set prescaler to old value*/
00252         adc->PRESCALER = prescaler_val;
00253 }

void ADC_Wait_8MHz ( ADC_t *  adc  ) 

This function waits until the adc common mode is settled.

After the ADC clock has been turned on, the common mode voltage in the ADC need some time to settle. The time it takes equals one dummy conversion. Instead of doing a dummy conversion this function waits until the common mode is settled.

Note:
The function sets the prescaler to the minimum value to minimize the time it takes the common mode to settle. If the clock speed is higher than 8 MHz use the ADC_wait_32MHz function.
Parameters:
adc Pointer to ADC module register section.

Definition at line 208 of file adc_driver.c.

Referenced by main().

00209 {
00210         /* Store old prescaler value. */
00211         uint8_t prescaler_val = adc->PRESCALER;
00212 
00213         /* Set prescaler value to minimum value. */
00214         adc->PRESCALER = ADC_PRESCALER_DIV4_gc;
00215 
00216         /* Wait 4*COMMON_MODE_CYCLES for common mode to settle. */
00217         delay_us(4*COMMON_MODE_CYCLES);
00218 
00219         /* Set prescaler to old value*/
00220         adc->PRESCALER = prescaler_val;
00221 }

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