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_11, ADC0_0, 0x02},
00032     {P0_12, ADC0_1, 0x02},
00033     {P0_13, ADC0_2, 0x02},
00034     {P0_14, ADC0_3, 0x02},
00035     {P0_15, ADC0_4, 0x02},
00036     {P0_16, ADC0_5, 0x01},
00037     {P0_22, ADC0_6, 0x01},
00038     {P0_23, ADC0_7, 0x01},
00039     {NC   , NC    , 0   }
00040 };
00041 
00042 #define LPC_IOCON0_BASE (LPC_IOCON_BASE)
00043 #define LPC_IOCON1_BASE (LPC_IOCON_BASE + 0x60)
00044 
00045 #define ADC_RANGE    ADC_10BIT_RANGE
00046 
00047 void analogin_init(analogin_t *obj, PinName pin) {
00048     obj->adc = (ADCName)pinmap_peripheral(pin, PinMap_ADC);
00049     if (obj->adc == (uint32_t)NC) {
00050         error("ADC pin mapping failed");
00051     }
00052     
00053     // Power up ADC
00054     LPC_SYSCON->PDRUNCFG &= ~ (1 << 4);
00055     LPC_SYSCON->SYSAHBCLKCTRL |= ((uint32_t)1 << 13);
00056 
00057     uint32_t pin_number = (uint32_t)pin;
00058     __IO uint32_t *reg = (pin_number < 32) ? (__IO uint32_t*)(LPC_IOCON0_BASE + 4 * pin_number) : (__IO uint32_t*)(LPC_IOCON1_BASE + 4 * (pin_number - 32));
00059 
00060     // set pin to ADC mode
00061     *reg &= ~(1 << 7); // set ADMODE = 0 (analog mode)
00062 
00063     uint32_t PCLK = SystemCoreClock;
00064     uint32_t MAX_ADC_CLK = 4500000;
00065     uint32_t clkdiv = div_round_up(PCLK, MAX_ADC_CLK) - 1;
00066 
00067     LPC_ADC->CR = (0 << 0)      // no channels selected
00068                 | (clkdiv << 8) // max of 4.5MHz
00069                 | (0 << 16)     // BURST = 0, software controlled
00070                 | ( 0 << 17 );  // CLKS = 0, not applicable
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 >> 6) & ADC_RANGE; // 10 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 << 6) | ((value >> 4) & 0x003F); // 10 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 }