#include "main.h"

uint16_t vref=0;
uint16_t vref_calibrated = 0;
uint16_t delta_vref = 0;
uint32_t wait=0;

int main(void)
{
	/* Enable peripheral clock */
	RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1, ENABLE);

	/* configure ADC */
	adc_config();

	// Read internal voltage reference calibrated value
	vref_calibrated = (*(uint16_t*)0x1FFFF7BA);

	while(1)
	{
	  // Start conversion for ADC1
		ADC_StartOfConversion(ADC1);
		// Wait until conversion is done
		while(ADC_GetFlagStatus(ADC1, ADC_FLAG_EOC) == RESET);
		// Read Vrefint value
		vref = ADC1->DR;
		// Calculate the difference between Vrefint measured and factory calibrated
		delta_vref = vref - vref_calibrated;
		// Add some delay
		for(wait = 0; wait < 0x0FFFFF; wait++);
	}
}

void adc_config(void)
{
	ADC_DeInit(ADC1); // De-init ADC1 peripheral

  adc_struct.ADC_Resolution = ADC_Resolution_12b; // 12 bit resolution
  adc_struct.ADC_ContinuousConvMode = DISABLE; 		// single conversion mode
  adc_struct.ADC_ExternalTrigConvEdge = ADC_ExternalTrigConvEdge_None;
  adc_struct.ADC_ExternalTrigConv = ADC_ExternalTrigConv_T1_TRGO;
  adc_struct.ADC_DataAlign = ADC_DataAlign_Right;
  adc_struct.ADC_ScanDirection = ADC_ScanDirection_Upward;
  ADC_Init(ADC1, &adc_struct);

  // Convert Vrefint channel
  ADC_ChannelConfig(ADC1, ADC_Channel_Vrefint, ADC_SampleTime_239_5Cycles);

	// Enable internal voltage reference channel
	ADC_VrefintCmd(ENABLE);

	// Enable ADC1 peripheral
	ADC_Cmd(ADC1, ENABLE);

	// wait until ADC1 peripheral is enabled
	while(!ADC_GetFlagStatus(ADC1, ADC_FLAG_ADRDY));
}