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RIOT/cpu/lm4f120/periph/adc.c 3.37 KB
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  /*
   * Copyright (C) 2016 Marc Poulhiès
   *
   * This file is subject to the terms and conditions of the GNU Lesser General
   * Public License v2.1. See the file LICENSE in the top level directory for more
   * details.
   */
  
  /**
   * @ingroup     cpu_lm4f120
   * @{
   *
   * @file
   * @brief       Low-level ADC driver implementation
   *
   * The current ADC driver implementation only supports ADC0.
   *
   * @author      Marc Poulhiès <dkm@kataplop.net>
   *
   * @}
   */
  
  #include <stdint.h>
  #include <string.h>
  
  #include "cpu.h"
  #include "mutex.h"
  #include "periph/adc.h"
  
  /*
   * @brief   ADC sequence used by this driver and oversampling settings
   * @{
   */
  #define SEQ             (3)
  #define OVERSAMPLE      (64)
  /** @} */
  
  /**
   * @brief   pin configuration parameters
   */
  struct adc_gpio_cfg_s {
      unsigned long gpio_base;
      unsigned long gpio_sysctl;
      unsigned short gpio_pin;
  };
  
  /**
   * @brief   Fixed ADC pin configuration
   */
  static const struct adc_gpio_cfg_s adc0_gpio[ADC_NUMOF] = {
      { GPIO_PORTE_BASE, SYSCTL_PERIPH_GPIOE, GPIO_PIN_3 }, /**< AIN0 */
      { GPIO_PORTE_BASE, SYSCTL_PERIPH_GPIOE, GPIO_PIN_2 }, /**< AIN1 */
      { GPIO_PORTE_BASE, SYSCTL_PERIPH_GPIOE, GPIO_PIN_1 }, /**< AIN2 */
      { GPIO_PORTE_BASE, SYSCTL_PERIPH_GPIOE, GPIO_PIN_0 }, /**< AIN3 */
      { GPIO_PORTD_BASE, SYSCTL_PERIPH_GPIOD, GPIO_PIN_3 }, /**< AIN4 */
      { GPIO_PORTD_BASE, SYSCTL_PERIPH_GPIOD, GPIO_PIN_2 }, /**< AIN5 */
      { GPIO_PORTD_BASE, SYSCTL_PERIPH_GPIOD, GPIO_PIN_1 }, /**< AIN6 */
      { GPIO_PORTD_BASE, SYSCTL_PERIPH_GPIOD, GPIO_PIN_0 }, /**< AIN7 */
      { GPIO_PORTE_BASE, SYSCTL_PERIPH_GPIOE, GPIO_PIN_5 }, /**< AIN8 */
      { GPIO_PORTE_BASE, SYSCTL_PERIPH_GPIOE, GPIO_PIN_4 }, /**< AIN9 */
      { GPIO_PORTB_BASE, SYSCTL_PERIPH_GPIOB, GPIO_PIN_4 }, /**< AIN10 */
      { GPIO_PORTB_BASE, SYSCTL_PERIPH_GPIOB, GPIO_PIN_5 }, /**< AIN11 */
  };
  
  /**
   * @brief   Lock to prevent concurrent access to the ADC
   */
  static mutex_t lock = MUTEX_INIT;
  
  static inline void prep(void)
  {
      mutex_lock(&lock);
      ROM_SysCtlPeripheralEnable(SYSCTL_PERIPH_ADC0);
  }
  
  static inline void done(void)
  {
      ROM_SysCtlPeripheralDisable(SYSCTL_PERIPH_ADC0);
      mutex_unlock(&lock);
  }
  
  int adc_init(adc_t line)
  {
      /* make sure the given ADC line is valid */
      if (line >= ADC_NUMOF) {
          return -1;
      }
  
      prep();
  
      ROM_SysCtlADCSpeedSet(SYSCTL_ADCSPEED_125KSPS);
      ROM_ADCHardwareOversampleConfigure(ADC0_BASE, OVERSAMPLE);
  
      ROM_SysCtlPeripheralEnable(adc0_gpio[line].gpio_sysctl);
      ROM_GPIOPinTypeADC(adc0_gpio[line].gpio_base, adc0_gpio[line].gpio_pin);
  
      done();
  
      return 0;
  }
  
  int adc_sample(adc_t line, adc_res_t res)
  {
      int value[2];
  
      if ((res != ADC_RES_10BIT) && (res != ADC_RES_12BIT)) {
          return -1;
      }
  
      prep();
  
      /* set channel */
      ROM_ADCSequenceConfigure(ADC0_BASE, SEQ, ADC_TRIGGER_PROCESSOR, 0);
      ROM_ADCSequenceStepConfigure(ADC0_BASE, SEQ, 0, line | ADC_CTL_IE | ADC_CTL_END);
      /* set resolution */
      ROM_ADCResolutionSet(ADC0_BASE, (unsigned long)res);
  
      /* start conversion and wait for results */
      ROM_ADCSequenceEnable(ADC0_BASE, SEQ);
      ROM_ADCIntClear(ADC0_BASE, SEQ);
      ROM_ADCProcessorTrigger(ADC0_BASE, SEQ);
      while (!ROM_ADCIntStatus(ADC0_BASE, SEQ, false)) {}
  
      /* get results */
      ROM_ADCSequenceDataGet(ADC0_BASE, SEQ, (unsigned long *) value);
  
      /* disable device again */
      ROM_ADCSequenceDisable(ADC0_BASE, SEQ);
      done();
  
      return value[0];
  }