tool/mbed/mbed-sdk/libraries/mbed/targets/hal/TARGET_NORDIC/TARGET_MCU_NRF51822/analogin_api.c

   1 /* mbed Microcontroller Library
   2  * Copyright (c) 2006-2013 ARM Limited
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at
   7  *
   8  *     http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16 #include "mbed_assert.h"
  17 #include "analogin_api.h"
  18 #include "cmsis.h"
  19 #include "pinmap.h"
  20
  21 #define ANALOGIN_MEDIAN_FILTER      1
  22 #define ADC_10BIT_RANGE             0x3FF
  23 #define ADC_RANGE    ADC_10BIT_RANGE
  24
  25 static const PinMap PinMap_ADC[] = {
  26     {p1, ADC0_0, 4},
  27     {p2, ADC0_0, 8},
  28     {p3, ADC0_0, 16},
  29     {p4, ADC0_0, 32},
  30     {p5, ADC0_0, 64},
  31     {p6, ADC0_0, 128},
  32     {NC, NC, 0}
  33 };
  34
  35 void analogin_init(analogin_t *obj, PinName pin)
  36 {
  37     int analogInputPin = 0;
  38     const PinMap *map  = PinMap_ADC;
  39
  40     obj->adc = (ADCName)pinmap_peripheral(pin, PinMap_ADC); //(NRF_ADC_Type *)
  41     MBED_ASSERT(obj->adc != (ADCName)NC);
  42
  43     while (map->pin != NC) {
  44         if (map->pin == pin) {
  45             analogInputPin = map->function;
  46             break;
  47         }
  48         map++;
  49     }
  50     obj->adc_pin = (uint8_t)analogInputPin;
  51
  52     NRF_ADC->ENABLE = ADC_ENABLE_ENABLE_Enabled;
  53     NRF_ADC->CONFIG = (ADC_CONFIG_RES_10bit << ADC_CONFIG_RES_Pos) |
  54                       (ADC_CONFIG_INPSEL_AnalogInputOneThirdPrescaling << ADC_CONFIG_INPSEL_Pos) |
  55                       (ADC_CONFIG_REFSEL_SupplyOneThirdPrescaling << ADC_CONFIG_REFSEL_Pos) |
  56                       (analogInputPin << ADC_CONFIG_PSEL_Pos) |
  57                       (ADC_CONFIG_EXTREFSEL_None << ADC_CONFIG_EXTREFSEL_Pos);
  58 }
  59
  60 uint16_t analogin_read_u16(analogin_t *obj)
  61 {
  62     NRF_ADC->CONFIG     &= ~ADC_CONFIG_PSEL_Msk;
  63     NRF_ADC->CONFIG     |= obj->adc_pin << ADC_CONFIG_PSEL_Pos;
  64     NRF_ADC->TASKS_START = 1;
  65     while (((NRF_ADC->BUSY & ADC_BUSY_BUSY_Msk) >> ADC_BUSY_BUSY_Pos) == ADC_BUSY_BUSY_Busy) {
  66     }
  67
  68     return (uint16_t)NRF_ADC->RESULT; // 10 bit
  69 }
  70
  71 float analogin_read(analogin_t *obj)
  72 {
  73     uint16_t value = analogin_read_u16(obj);
  74     return (float)value * (1.0f / (float)ADC_RANGE);
  75 }