tool/mbed/mbed-sdk/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC408X/TARGET_LPC4088/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 #include "mbed_error.h"
  21
  22 #define ANALOGIN_MEDIAN_FILTER      1
  23
  24 #define ADC_10BIT_RANGE             0x3FF
  25 #define ADC_12BIT_RANGE             0xFFF
  26
  27 static inline int div_round_up(int x, int y) {
  28   return (x + (y - 1)) / y;
  29 }
  30
  31 static const PinMap PinMap_ADC[] = {
  32     {P0_23, ADC0_0, 0x01},
  33     {P0_24, ADC0_1, 0x01},
  34     {P0_25, ADC0_2, 0x01},
  35     {P0_26, ADC0_3, 0x01},
  36     {P1_30, ADC0_4, 0x03},
  37     {P1_31, ADC0_5, 0x03},
  38     {P0_12, ADC0_6, 0x03},
  39     {P0_13, ADC0_7, 0x03},
  40     {NC   , NC    , 0   }
  41 };
  42
  43 #define ADC_RANGE    ADC_12BIT_RANGE
  44
  45 void analogin_init(analogin_t *obj, PinName pin) {
  46     obj->adc = (ADCName)pinmap_peripheral(pin, PinMap_ADC);
  47     MBED_ASSERT(obj->adc != (ADCName)NC);
  48
  49     // ensure power is turned on
  50     LPC_SC->PCONP |= (1 << 12);
  51
  52     uint32_t PCLK = PeripheralClock;
  53
  54     // calculate minimum clock divider
  55     //  clkdiv = divider - 1
  56     uint32_t MAX_ADC_CLK = 12400000;
  57     uint32_t clkdiv = div_round_up(PCLK, MAX_ADC_CLK) - 1;
  58
  59     // Set the generic software-controlled ADC settings
  60     LPC_ADC->CR = (0 << 0)      // SEL: 0 = no channels selected
  61                   | (clkdiv << 8) // CLKDIV:
  62                   | (0 << 16)     // BURST: 0 = software control
  63                   | (1 << 21)     // PDN: 1 = operational
  64                   | (0 << 24)     // START: 0 = no start
  65                   | (0 << 27);    // EDGE: not applicable
  66
  67     // must enable analog mode (ADMODE = 0)
  68     __IO uint32_t *reg = (__IO uint32_t*) (LPC_IOCON_BASE + 4 * pin);
  69     *reg &= ~(1 << 7);
  70
  71     pinmap_pinout(pin, PinMap_ADC);
  72 }
  73
  74 static inline uint32_t adc_read(analogin_t *obj) {
  75     // Select the appropriate channel and start conversion
  76     LPC_ADC->CR &= ~0xFF;
  77     LPC_ADC->CR |= 1 << (int)obj->adc;
  78     LPC_ADC->CR |= 1 << 24;
  79
  80     // Repeatedly get the sample data until DONE bit
  81     unsigned int data;
  82     do {
  83         data = LPC_ADC->GDR;
  84     } while ((data & ((unsigned int)1 << 31)) == 0);
  85
  86     // Stop conversion
  87     LPC_ADC->CR &= ~(1 << 24);
  88
  89     return (data >> 4) & ADC_RANGE; // 12 bit
  90 }
  91
  92 static inline void order(uint32_t *a, uint32_t *b) {
  93     if (*a > *b) {
  94         uint32_t t = *a;
  95         *a = *b;
  96         *b = t;
  97     }
  98 }
  99
 100 static inline uint32_t adc_read_u32(analogin_t *obj) {
 101     uint32_t value;
 102 #if ANALOGIN_MEDIAN_FILTER
 103     uint32_t v1 = adc_read(obj);
 104     uint32_t v2 = adc_read(obj);
 105     uint32_t v3 = adc_read(obj);
 106     order(&v1, &v2);
 107     order(&v2, &v3);
 108     order(&v1, &v2);
 109     value = v2;
 110 #else
 111     value = adc_read(obj);
 112 #endif
 113     return value;
 114 }
 115
 116 uint16_t analogin_read_u16(analogin_t *obj) {
 117     uint32_t value = adc_read_u32(obj);
 118
 119     return (value << 4) | ((value >> 8) & 0x000F); // 12 bit
 120 }
 121
 122 float analogin_read(analogin_t *obj) {
 123     uint32_t value = adc_read_u32(obj);
 124     return (float)value * (1.0f / (float)ADC_RANGE);
 125 }