#include "stm32l1xx.h"

volatile uint16_t adcConversions[2];
volatile uint32_t avg_value1, avg_value2;
volatile uint8_t samples;


// function prototypes
void InitGPIO();
void InitDMA();
void InitADC();


// main program
int main()
{

	// start system 12 MHz
 	SystemInit();

 	// initialize peripheral
 	InitGPIO();
 	InitDMA();
 	InitADC();

 	while(1)
 	{
 	}
}


// DMA interrupt handler
void DMA1_Channel1_IRQHandler()
{
	DMA_ClearITPendingBit(DMA1_IT_TC1);
	// in this handler isn't much time. just do essential things

	avg_value1 += adcConversions[0];
	avg_value2 += adcConversions[1];

	samples++;
}

void InitGPIO()
{
	RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOB, ENABLE);

	GPIO_InitTypeDef GPIOInitStruct;
	// initialize analog input pin (PB13)
	GPIOInitStruct.GPIO_Pin = GPIO_Pin_12 | GPIO_Pin_13;
	GPIOInitStruct.GPIO_Mode = GPIO_Mode_AN;
	GPIOInitStruct.GPIO_OType = GPIO_OType_PP;
	GPIOInitStruct.GPIO_PuPd = GPIO_PuPd_NOPULL;
	GPIOInitStruct.GPIO_Speed = GPIO_Speed_400KHz;
	GPIO_Init(GPIOB, &GPIOInitStruct);
}


void InitADC()
{
	// turn on clock for ADC1
	RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1, ENABLE);

	// initialize ADC
	ADC_InitTypeDef ADCInitStruct;
	ADCInitStruct.ADC_Resolution = ADC_Resolution_10b;
	ADCInitStruct.ADC_ScanConvMode = ENABLE;
	ADCInitStruct.ADC_ContinuousConvMode = DISABLE;
	ADCInitStruct.ADC_ExternalTrigConvEdge = ADC_ExternalTrigConvEdge_Rising;
	ADCInitStruct.ADC_ExternalTrigConv = ADC_ExternalTrigConv_T6_TRGO; // use hardware trigger: timer TIM6
	ADCInitStruct.ADC_DataAlign = ADC_DataAlign_Right;
	ADCInitStruct.ADC_NbrOfConversion = 2;
	ADC_Init(ADC1, &ADCInitStruct);

	// channel configuration
	ADC_RegularChannelConfig(ADC1, ADC_Channel_18, 1, ADC_SampleTime_4Cycles); // use channel 18 (PB12)
	ADC_RegularChannelConfig(ADC1, ADC_Channel_19, 2, ADC_SampleTime_4Cycles); // use channel 19 (PB13)

	// enable DMA request after last transfer (Single-ADC mode)
	ADC_DMARequestAfterLastTransferCmd(ADC1, ENABLE);

	// turn on clock for timer TIM6
	RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM6, ENABLE);

	// initialize timer
	TIM_TimeBaseInitTypeDef TIMInitStruct;
	TIMInitStruct.TIM_Prescaler = 1;
	TIMInitStruct.TIM_Period = 100;
	TIMInitStruct.TIM_ClockDivision = 1;
	TIM_TimeBaseInit(TIM6, &TIMInitStruct);

	// trigger mode: update
	TIM_SelectOutputTrigger(TIM6, TIM_TRGOSource_Update);

	ADC_DMACmd(ADC1, ENABLE);
	// enable ADC1
	ADC_Cmd(ADC1, ENABLE);
	// enable timer
	TIM_Cmd(TIM6, ENABLE);

 	// turn on HSI (required for ADC)
 	RCC_HSICmd(ENABLE);
 	while(!RCC_GetFlagStatus(RCC_FLAG_HSIRDY));
}


void InitDMA()
{
	// turn on clock for DMA
	RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);

	// configure DMA
	DMA_InitTypeDef DMA_InitStructure;
	DMA_DeInit(DMA1_Channel1);
	DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)&ADC1->DR;
	DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)&adcConversions;
	DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;
	DMA_InitStructure.DMA_BufferSize = 2;
	DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
	DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
	DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord;
	DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord;
	DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;
	DMA_InitStructure.DMA_Priority = DMA_Priority_High;
	DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
	DMA_Init(DMA1_Channel1, &DMA_InitStructure);

	// enable interrupt for DMA
	DMA_ITConfig(DMA1_Channel1, DMA_IT_TC, ENABLE);

	// initialize interrupt for DMA
	NVIC_InitTypeDef INTInitStructDMA;
	INTInitStructDMA.NVIC_IRQChannel = DMA1_Channel1_IRQn;
	INTInitStructDMA.NVIC_IRQChannelCmd = ENABLE;
	INTInitStructDMA.NVIC_IRQChannelPreemptionPriority = 0;
	INTInitStructDMA.NVIC_IRQChannelSubPriority = 0;
	NVIC_Init(&INTInitStructDMA);

	// enable DMA
	DMA_Cmd(DMA1_Channel1, ENABLE);
}