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/*
* The MIT License (MIT)
*
* Copyright (c) 2016 Matthias P. Braendli, Maximilien Cuony
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
#include "analog_input.h"
#include "stm32f4xx_adc.h"
#include <math.h>
void analog_init(void)
{
// Enable ADC and GPIOA clocks
RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1, ENABLE);
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);
// Set Pin PA5 to analog input
GPIO_InitTypeDef GPIO_InitStructure;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AN;
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_5;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_Init(GPIOA, &GPIO_InitStructure);
// Init ADC1 for supply measurement
ADC_CommonInitTypeDef ADC_CommonInitStruct;
ADC_CommonInitStruct.ADC_Mode = ADC_Mode_Independent;
ADC_CommonInitStruct.ADC_Prescaler = ADC_Prescaler_Div8;
ADC_CommonInitStruct.ADC_DMAAccessMode = ADC_DMAAccessMode_Disabled;
ADC_CommonInitStruct.ADC_TwoSamplingDelay = ADC_TwoSamplingDelay_5Cycles;
ADC_CommonInit(&ADC_CommonInitStruct);
ADC_InitTypeDef ADC_InitStruct;
ADC_InitStruct.ADC_Resolution = ADC_Resolution_12b;
ADC_InitStruct.ADC_ScanConvMode = DISABLE;
ADC_InitStruct.ADC_ContinuousConvMode = ENABLE;
ADC_InitStruct.ADC_ExternalTrigConvEdge = ADC_ExternalTrigConvEdge_None;
ADC_InitStruct.ADC_ExternalTrigConv = ADC_ExternalTrigConv_T1_CC1;
ADC_InitStruct.ADC_DataAlign = ADC_DataAlign_Right;
ADC_InitStruct.ADC_NbrOfConversion = 1;
ADC_Init(ADC1, &ADC_InitStruct);
// Configure ADC1 to use the converted 12V signal (see schematics)
const uint8_t rank = 1;
ADC_RegularChannelConfig(ADC1,
ADC_Channel_5,
rank,
ADC_SampleTime_480Cycles);
// Enable ADC
ADC_Cmd(ADC1, ENABLE);
}
float analog_measure_12v(void)
{
ADC_SoftwareStartConv(ADC1); //Start the conversion
// TODO add timeout
while (ADC_GetFlagStatus(ADC1, ADC_FLAG_EOC) == RESET);
const uint16_t raw_value = ADC_GetConversionValue(ADC1);
const float adc_max_value = (1 << 12);
const float v_ref = 2.965f;
// Convert ADC measurement to voltage
float voltage = ((float)raw_value*v_ref/adc_max_value);
// Compensate resistor divider on board (see schematic)
return voltage * 202.0f / 22.0f;
}
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