Atmel Software Framework

adc_example2_gfx.c File Reference

AVR XMEGA Analog to Digital Converter Driver Example 2.

Copyright (c) 2011-2015 Atmel Corporation. All rights reserved.

#include <conf_example.h>
#include <stdio.h>
#include <asf.h>

Data Structures

struct  calibration_data
 ADC calibration data. More...
 

Macros

#define IDEAL_GAIN_RESULT   900
 Ideal ADC result at 0.9 V. More...
 

Functions

static uint16_t get_mean_sample_value (void)
 Get mean sample value. More...
 
 ISR (ADCB_CH0_vect)
 Interrupt Service Routine for channel 0 on ADC B. More...
 
int main (void)
 
static void mdelay (uint16_t ms)
 Delay for ms milliseconds. More...
 
static void wait_for_button (void)
 Wait for button press and release. More...
 

Variables

static struct calibration_data cal_data
 
static volatile uint16_t last_sample
 Offset- and gain-compensated sample value. More...
 

#define IDEAL_GAIN_RESULT   900

Ideal ADC result at 0.9 V.

This factor is given by the following equation:

\[ R_\textnormal{ideal}(U) = 2^{12} \cdot \frac{U_\textnormal{measured}} {U_\textnormal{reference}} \]

For a 1 V reference and 0.9 V input, the expected result from an unsigned, 12-bit conversion is 3686.

Note
To make the example compute the voltage in milliVolts, change this we set the factor to 900.

Referenced by ISR().

static uint16_t get_mean_sample_value ( void  )
static

Get mean sample value.

Performs 2 to the power of OVERSAMPLING_FACTOR successive conversions, and computes the mean value of the resulting sample values.

Returns
Mean sample value.

References ADC_CH0, adc_get_result, adc_start_conversion(), and adc_wait_for_interrupt_flag().

Referenced by main().

ISR ( ADCB_CH0_vect  )

Interrupt Service Routine for channel 0 on ADC B.

Upon completed AD conversion, this ISR computes a calibrated sample from the ADC result, then stores it in a global variable before triggering a new conversion.

References ADC_CH0, adc_get_result, adc_start_conversion(), cal_data, calibration_data::gain, gfx_mono_draw_string(), IDEAL_GAIN_RESULT, last_sample, calibration_data::offset, and sysfont.

static void mdelay ( uint16_t  ms)
static

Delay for ms milliseconds.

Parameters
msnumber of milliseconds to busy wait.

References sysclk_get_cpu_hz().

Referenced by main(), and wait_for_button().

static void wait_for_button ( void  )
static

Wait for button press and release.

Waits for the button connected to BUTTON_PIN to be pressed and released. Debouncing is done with an approximate 20 ms delay after both the press and the release.

References ioport_pin_is_high(), ioport_pin_is_low(), and mdelay().

Referenced by main().

struct calibration_data cal_data
static

Referenced by ISR(), and main().

volatile uint16_t last_sample
static

Offset- and gain-compensated sample value.

Referenced by ISR().