analogin_api.c

00001 /* mbed Microcontroller Library
00002  * Copyright (c) 2006-2013 ARM Limited
00003  *
00004  * Licensed under the Apache License, Version 2.0 (the "License");
00005  * you may not use this file except in compliance with the License.
00006  * You may obtain a copy of the License at
00007  *
00008  *     http://www.apache.org/licenses/LICENSE-2.0
00009  *
00010  * Unless required by applicable law or agreed to in writing, software
00011  * distributed under the License is distributed on an "AS IS" BASIS,
00012  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00013  * See the License for the specific language governing permissions and
00014  * limitations under the License.
00015  */
00016 #include "analogin_api.h"
00017 #include "cmsis.h"
00018 #include "pinmap.h"
00019 #include "error.h"
00020 
00021 #define ANALOGIN_MEDIAN_FILTER      1
00022 
00023 #define ADC_10BIT_RANGE             0x3FF
00024 #define ADC_12BIT_RANGE             0xFFF
00025 
00026 static inline int div_round_up(int x, int y) {
00027   return (x + (y - 1)) / y;
00028 }
00029 
00030 static const PinMap PinMap_ADC[] = {
00031     {P0_23, ADC0_0, 0x01},
00032     {P0_24, ADC0_1, 0x01},
00033     {P0_25, ADC0_2, 0x01},
00034     {P0_26, ADC0_3, 0x01},
00035     {P1_30, ADC0_4, 0x03},
00036     {P1_31, ADC0_5, 0x03},
00037     {P0_12, ADC0_6, 0x03},
00038     {P0_13, ADC0_7, 0x03},
00039     {NC   , NC    , 0   }
00040 };
00041 
00042 #define ADC_RANGE    ADC_12BIT_RANGE
00043 
00044 void analogin_init(analogin_t *obj, PinName pin) {
00045     obj->adc = (ADCName)pinmap_peripheral(pin, PinMap_ADC);
00046     if (obj->adc == (uint32_t)NC) {
00047         error("ADC pin mapping failed");
00048     }
00049     
00050     // ensure power is turned on
00051     LPC_SC->PCONP |= (1 << 12);
00052     
00053     uint32_t PCLK = PeripheralClock ;
00054     
00055     // calculate minimum clock divider
00056     //  clkdiv = divider - 1
00057     uint32_t MAX_ADC_CLK = 12400000;
00058     uint32_t clkdiv = div_round_up(PCLK, MAX_ADC_CLK) - 1;
00059     
00060     // Set the generic software-controlled ADC settings
00061     LPC_ADC->CR = (0 << 0)      // SEL: 0 = no channels selected
00062                   | (clkdiv << 8) // CLKDIV:
00063                   | (0 << 16)     // BURST: 0 = software control
00064                   | (1 << 21)     // PDN: 1 = operational
00065                   | (0 << 24)     // START: 0 = no start
00066                   | (0 << 27);    // EDGE: not applicable
00067     
00068     // must enable analog mode (ADMODE = 0)
00069     __IO uint32_t *reg = (__IO uint32_t*) (LPC_IOCON_BASE + 4 * pin);
00070     *reg &= ~(1 << 7);
00071     
00072     pinmap_pinout(pin, PinMap_ADC);
00073 }
00074 
00075 static inline uint32_t adc_read(analogin_t *obj) {
00076     // Select the appropriate channel and start conversion
00077     LPC_ADC->CR &= ~0xFF;
00078     LPC_ADC->CR |= 1 << (int)obj->adc;
00079     LPC_ADC->CR |= 1 << 24;
00080 
00081     // Repeatedly get the sample data until DONE bit
00082     unsigned int data;
00083     do {
00084         data = LPC_ADC->GDR;
00085     } while ((data & ((unsigned int)1 << 31)) == 0);
00086 
00087     // Stop conversion
00088     LPC_ADC->CR &= ~(1 << 24);
00089     
00090     return (data >> 4) & ADC_RANGE; // 12 bit
00091 }
00092 
00093 static inline void order(uint32_t *a, uint32_t *b) {
00094     if (*a > *b) {
00095         uint32_t t = *a;
00096         *a = *b;
00097         *b = t;
00098     }
00099 }
00100 
00101 static inline uint32_t adc_read_u32(analogin_t *obj) {
00102     uint32_t value;
00103 #if ANALOGIN_MEDIAN_FILTER
00104     uint32_t v1 = adc_read(obj);
00105     uint32_t v2 = adc_read(obj);
00106     uint32_t v3 = adc_read(obj);
00107     order(&v1, &v2);
00108     order(&v2, &v3);
00109     order(&v1, &v2);
00110     value = v2;
00111 #else
00112     value = adc_read(obj);
00113 #endif
00114     return value;
00115 }
00116 
00117 uint16_t analogin_read_u16(analogin_t *obj) {
00118     uint32_t value = adc_read_u32(obj);
00119     
00120     return (value << 4) | ((value >> 8) & 0x000F); // 12 bit
00121 }
00122 
00123 float analogin_read(analogin_t *obj) {
00124     uint32_t value = adc_read_u32(obj);
00125     return (float)value * (1.0f / (float)ADC_RANGE);
00126 }