#include "gd32_adc.h"
#include "gpio.h"
#include "clock.h"
/* For 12-bits resolution, the total conversion time is 
 *sampling time + 12.5 ADCCLK cycles 
 *all channel is enabled oversample to reach 16bit accurate
*/
void adc_init(void){
	rcu_periph_clock_enable(RCU_GPIOA);
	rcu_periph_clock_enable(RCU_GPIOB);	
	gpio_mode_analog_input(GPIOA, GPIO_PIN_1|GPIO_PIN_4|GPIO_PIN_5|GPIO_PIN_6|GPIO_PIN_7);
	gpio_mode_analog_input(GPIOB, GPIO_PIN_1|GPIO_PIN_0);

    /* config ADC clock */
    rcu_adc_clock_config(RCU_ADCCK_AHB_DIV3); //adc clock:28M 

	rcu_periph_clock_enable(RCU_ADC);
	adc_deinit();
    /* ADC trigger config */
    adc_external_trigger_source_config(ADC_REGULAR_CHANNEL, ADC_EXTTRIG_REGULAR_NONE);
	/* ADC data alignment config */
	adc_data_alignment_config(ADC_DATAALIGN_RIGHT);
	/* ADC channel length config */
	adc_channel_length_config(ADC_REGULAR_CHANNEL, 1);

	adc_resolution_config(ADC_RESOLUTION_12B);
 
	//adc_special_function_config(ADC_SCAN_MODE,ENABLE);

	adc_discontinuous_mode_config(ADC_REGULAR_CHANNEL, 1);

	adc_external_trigger_config(ADC_REGULAR_CHANNEL, ENABLE);

}

int adc_sample(int chan, int calibration){
	int value = -0xFFFFFF;
	int mask = 0xFFFF;
	//hardware oversample to 16bit
	adc_oversample_mode_config(ADC_OVERSAMPLING_ALL_CONVERT, ADC_OVERSAMPLING_SHIFT_4B, ADC_OVERSAMPLING_RATIO_MUL256);
	adc_oversample_mode_enable();

    /* use max convert time to make sure the adc work fine */
    adc_regular_channel_config(0, chan, ADC_SAMPLETIME_239POINT5);//239.5 + 12.5 = 242 cycle, 242/(28*1000000)
	adc_enable();
	delay_us(1000); //MUST delay, for adc work fine
	if (calibration) {
		/* ADC calibration and reset calibration */
    	adc_calibration_enable();
	}
	
	adc_software_trigger_enable(ADC_REGULAR_CHANNEL);
    while(SET != adc_flag_get(ADC_FLAG_EOC));
    value = adc_regular_data_read();
	adc_flag_clear(ADC_FLAG_EOC);
	adc_disable();

	return value & mask;
}