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https://github.com/RIOT-OS/RIOT.git
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117 lines
3.4 KiB
C
117 lines
3.4 KiB
C
/*
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* Copyright (C) 2017 HAW Hamburg
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*
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* This file is subject to the terms and conditions of the GNU Lesser
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* General Public License v2.1. See the file LICENSE in the top level
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* directory for more details.
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*/
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/**
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* @ingroup cpu_cc2538
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* @ingroup drivers_periph_adc
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* @{
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*
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* @file
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* @brief Low-level ADC driver implementation
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*
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* @notice based on TI peripheral drivers library
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*
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* @author Sebastian Meiling <s@mlng.net>
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* @}
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*/
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#include "vendor/hw_memmap.h"
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#include "vendor/hw_soc_adc.h"
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#include "board.h"
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#include "cpu.h"
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#include "periph_conf.h"
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#include "periph_cpu.h"
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#include "periph/adc.h"
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#define ENABLE_DEBUG 0
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#include "debug.h"
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static cc2538_soc_adc_t *soc_adc = (cc2538_soc_adc_t *)SOC_ADC_BASE;
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int adc_init(adc_t line)
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{
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if (line >= ADC_NUMOF) {
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DEBUG("adc_init: invalid ADC line (%d)!\n", line);
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return -1;
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}
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/* stop random number generator, and set STSEL = 1 */
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soc_adc->ADCCON1 = (SOC_ADC_ADCCON1_STSEL_M | SOC_ADC_ADCCON1_RCTRL_M);
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/* disable any DMA, continuous ADC settings */
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soc_adc->ADCCON2 = 0x0;
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/* configure ADC GPIO as analog input */
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gpio_init(adc_config[line], GPIO_IN_ANALOG);
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return 0;
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}
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int32_t adc_sample(adc_t line, adc_res_t res)
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{
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/* check if adc line valid */
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if (line >= ADC_NUMOF) {
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DEBUG("adc_sample: invalid ADC line!\n");
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return -1;
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}
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uint8_t rshift;
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/* check if given resolution valid, and set right shift */
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switch(res) {
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case ADC_RES_7BIT:
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rshift = SOCADC_7_BIT_RSHIFT;
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break;
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case ADC_RES_9BIT:
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rshift = SOCADC_9_BIT_RSHIFT;
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break;
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case ADC_RES_10BIT:
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rshift = SOCADC_10_BIT_RSHIFT;
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break;
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case ADC_RES_12BIT:
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rshift = SOCADC_12_BIT_RSHIFT;
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break;
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default:
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DEBUG("adc_sample: invalid resolution!\n");
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return -1;
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}
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/**
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* @attention CC2538 ADC supports differential comparison of two analog
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* GPIO inputs, hence negative values are possible. RIOT currently allows
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* positive ADC output only. Thus, reduce shift by one to compensate and
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* get full value range according to ADC resolution. E.g. 10 Bit resolution
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* with diff ADC would have [-512,511] range but RIOT expects [0,1023].
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*/
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rshift--;
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/* configure adc line with parameters and trigger a single conversion*/
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uint32_t reg = (soc_adc->ADCCON3) & ~(SOC_ADC_ADCCON3_EREF_M |
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SOC_ADC_ADCCON3_EDIV_M |
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SOC_ADC_ADCCON3_ECH_M);
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soc_adc->ADCCON3 = reg | res | SOC_ADC_ADCCON3_EREF |
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(adc_config[line] & GPIO_PIN_MASK);
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DEBUG("ADCCON1: %"PRIu32" ADCCON2: %"PRIu32" ADCCON3: %"PRIu32"\n",
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soc_adc->ADCCON1, soc_adc->ADCCON2, soc_adc->ADCCON3);
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/* Poll/wait until end of conversion */
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while ((soc_adc->ADCCON1 & SOC_ADC_ADCCON1_EOC_M) == 0) {}
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/* Read result after conversion completed,
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* reading SOC_ADC_ADCH last will clear SOC_ADC_ADCCON1.EOC */
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int16_t sample = soc_adc->ADCL & SOC_ADC_ADCL_ADC_M;
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sample |= (soc_adc->ADCH & SOC_ADC_ADCH_ADC_M) << 8;
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/* sample right shifted depending on resolution */
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sample = sample >> rshift;
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DEBUG("adc_sample: raw value %"PRIi16"\n", sample);
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/* FIXME: currently RIOT ADC allows values >0 only */
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if (sample < 0) {
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sample = 0;
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}
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return (int)sample;
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}
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