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134 lines
3.3 KiB
C
134 lines
3.3 KiB
C
/*
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* Copyright (C) 2014 Freie Universität Berlin
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* Copyright (C) 2015 Ludwig Knüpfer
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*
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* This file is subject to the terms and conditions of the GNU Lesser General
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* Public License v2.1. See the file LICENSE in the top level directory for more
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* details.
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*/
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/**
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* @ingroup cpu_nrf51822
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* @{
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*
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* @file
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* @brief Low-level UART driver implementation
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*
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* @author Hauke Petersen <hauke.petersen@fu-berlin.de>
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* @author Ludwig Knüpfer <ludwig.knuepfer@fu-berlin.de>
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*
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* @}
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*/
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#include "cpu.h"
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#include "periph/adc.h"
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#include "periph_conf.h"
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/* guard file in case no ADC device is defined */
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#if ADC_NUMOF
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/* save the maximum value configured for the ADC */
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int adc_max_value;
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int adc_init(adc_t dev, adc_precision_t precision)
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{
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/* the NRF51822 only supports one ADC... */
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if (dev != ADC_0) {
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return -2;
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}
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/* power on ADC */
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NRF_ADC->POWER = 1;
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/* disable ADC interrupts */
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NRF_ADC->INTENSET = (ADC_INTENSET_END_Disabled << ADC_INTENSET_END_Pos);
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/* configure ADC, set precision, internal reference to VBG */
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switch (precision) {
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case ADC_RES_8BIT:
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adc_max_value = 255;
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NRF_ADC->CONFIG = (ADC_CONFIG_RES_8bit << ADC_CONFIG_RES_Pos);
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break;
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case ADC_RES_10BIT:
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adc_max_value = 1023;
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NRF_ADC->CONFIG = (ADC_CONFIG_RES_10bit << ADC_CONFIG_RES_Pos);
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break;
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default:
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NRF_ADC->POWER = 0;
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return -1;
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}
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/* select the reference voltage / prescaler */
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NRF_ADC->CONFIG |= (ADC_CONFIG_EXTREFSEL_None << ADC_CONFIG_EXTREFSEL_Pos);
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NRF_ADC->CONFIG |= (ADC_CONFIG_REFSEL_VBG << ADC_CONFIG_REFSEL_Pos);
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NRF_ADC->CONFIG |= (ADC_CONFIG_INPSEL_AnalogInputOneThirdPrescaling << ADC_CONFIG_INPSEL_Pos);
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/* enable the ADC */
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NRF_ADC->ENABLE = (ADC_ENABLE_ENABLE_Enabled << ADC_ENABLE_ENABLE_Pos);
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return 0;
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}
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int adc_sample(adc_t dev, int channel)
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{
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if (dev != ADC_0) {
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return -2;
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}
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/* set channel */
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NRF_ADC->CONFIG &= ~(ADC_CONFIG_PSEL_Msk);
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NRF_ADC->CONFIG |= (ADC_CONFIG_PSEL_Disabled << ADC_CONFIG_PSEL_Pos);
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switch (channel) {
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case 0:
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NRF_ADC->CONFIG |= (ADC_0_CH0 << ADC_CONFIG_PSEL_Pos);
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break;
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case 1:
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NRF_ADC->CONFIG |= (ADC_0_CH1 << ADC_CONFIG_PSEL_Pos);
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break;
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case 2:
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NRF_ADC->CONFIG |= (ADC_0_CH2 << ADC_CONFIG_PSEL_Pos);
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break;
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case 3:
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NRF_ADC->CONFIG |= (ADC_0_CH3 << ADC_CONFIG_PSEL_Pos);
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break;
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default:
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return -1;
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}
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/* start conversion */
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NRF_ADC->TASKS_START = 1;
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/* wait for conversion to be complete */
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while (((NRF_ADC->BUSY & ADC_BUSY_BUSY_Msk) >> ADC_BUSY_BUSY_Pos) == ADC_BUSY_BUSY_Busy);
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NRF_ADC->EVENTS_END = 1;
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/* return result */
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return (int)NRF_ADC->RESULT;
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}
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void adc_poweron(adc_t dev)
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{
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if (dev == ADC_0) {
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NRF_ADC->POWER = 1;
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}
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}
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void adc_poweroff(adc_t dev)
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{
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if (dev == ADC_0) {
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NRF_ADC->POWER = 0;
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}
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}
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int adc_map(adc_t dev, int value, int min, int max)
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{
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return (int)adc_mapf(dev, value, (float)min, (float)max);
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}
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float adc_mapf(adc_t dev, int value, float min, float max)
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{
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return ((max - min) / ((float)adc_max_value)) * value;
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}
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#endif /* ADC_NUMOF */
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