light_sensor.c

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//////////////////////////////////////////////////////////////////////////////////
/// \file heivs/light_sensor.c
/// \brief ARMEBS4 light sensor access functions
/// \author Pascal Sartoretti / Marc Pignat
//////////////////////////////////////////////////////////////////////////////////
#include "heivs/light_sensor.h"
#include "stm32/stm32f4xx_rcc.h"
#include "heivs/stm32_gpio.h"
#include "stm32/stm32f4xx_adc.h"

//////////////////////////////////////////////////////////////////////////////////
/// \brief Initialise ADC to measure light sensor
//////////////////////////////////////////////////////////////////////////////////
void light_sensor_init(void)
{
    ADC_InitTypeDef ADC_init_structure;
    GPIO_InitTypeDef GPIO_initStructre; //Structure for analog input pin
    //Clock configuration
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC2,ENABLE);//The ADC1 is connected the APB2 peripheral bus thus we will use its clock source
    RCC_AHB1PeriphClockCmd(RCC_AHB1ENR_GPIOCEN,ENABLE);//Clock for the ADC port!! Do not forget about this one ;)
    //Analog pin configuration
    GPIO_initStructre.GPIO_Pin = GPIO_Pin_3;//The pin PC3 is connected to the potentiometer
    GPIO_initStructre.GPIO_Mode = GPIO_Mode_AN; //Set it as analog
    GPIO_initStructre.GPIO_PuPd = GPIO_PuPd_NOPULL; //We don't need any pull up or pull down
    GPIO_Init(GPIOC,&GPIO_initStructre);//Affecting the port with the initialization structure configuration
    //ADC structure configuration
    ADC_DeInit();
    ADC_init_structure.ADC_DataAlign = ADC_DataAlign_Right;//data converted will be shifted to right
    ADC_init_structure.ADC_Resolution = ADC_Resolution_12b;//Input voltage is converted into a 12bit number giving a maximum value of 4096
    ADC_init_structure.ADC_ContinuousConvMode = ENABLE; //the conversion is continuous, the input data is converted more than once
    ADC_init_structure.ADC_ExternalTrigConv = ADC_ExternalTrigConv_T1_CC1;// conversion is synchronous with TIM1 and CC1 (actually I'm not sure about this one :/)
    ADC_init_structure.ADC_ExternalTrigConvEdge = ADC_ExternalTrigConvEdge_None;//no trigger for conversion
    ADC_init_structure.ADC_NbrOfConversion = 1;//I think this one is clear :p
    ADC_init_structure.ADC_ScanConvMode = DISABLE;//The scan is configured in one channel
    ADC_Init(ADC2,&ADC_init_structure);//Initialize ADC with the previous configuration
    //Enable ADC conversion
    ADC_Cmd(ADC2,ENABLE);
    //Select the channel to be read from
    ADC_RegularChannelConfig(ADC2,ADC_Channel_13,1,ADC_SampleTime_144Cycles);
}

//////////////////////////////////////////////////////////////////////////////////
/// \brief Measure the light_sensor value
/// \return Measured value between 0 to 4095
/// Higher is the value when lower is the light
//////////////////////////////////////////////////////////////////////////////////
uint32_t light_sensor_value(void)
{
#define NB_SAMPLE   16
    uint32_t result=0;
    uint8_t i;
    // just an average because ADC is very poor
    for(i=0;i<NB_SAMPLE;i++)
    {
        ADC_SoftwareStartConv(ADC2);
        while(!ADC_GetFlagStatus(ADC2, ADC_FLAG_EOC));
        result += ADC_GetConversionValue(ADC2);
    }
    return result / NB_SAMPLE;
}