adc_example2_gfx.c File Reference

AVR XMEGA Analog to Digital Converter Driver Example 2.

Copyright (c) 2011-2018 Microchip Technology Inc. and its subsidiaries.

#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.

int main

(

void

)

References ADC_CH0, adc_enable(), adc_read_configuration(), ADC_REF_BANDGAP, ADC_RES_12, adc_set_clock_rate(), adc_set_conversion_parameters(), adc_set_conversion_trigger(), ADC_SIGN_OFF, adc_start_conversion(), ADC_TRIG_MANUAL, adc_wait_for_interrupt_flag(), adc_write_configuration(), adcch_disable_interrupt(), adcch_enable_interrupt(), ADCCH_MODE_COMPLETE, ADCCH_NEG_NONE, adcch_read_configuration(), adcch_set_input(), adcch_set_interrupt_mode(), adcch_write_configuration(), board_init(), cal_data, cpu_irq_enable, calibration_data::gain, get_mean_sample_value(), gfx_mono_init, ioport_set_pin_high(), ioport_set_pin_low(), calibration_data::offset, sleepmgr_enter_sleep(), sleepmgr_init(), sysclk_init, and wait_for_button().

static void mdelay ( uint16_t  ms )

static

Delay for ms milliseconds.

Parameters

ms	number 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().