Photoresist for learning of Blue Bridge Cup embedded expansion board

Hardware circuit

LM393 The voltage comparator pins are as follows


Photosensitive resistor

The acquisition of analog quantity uses stm32 Of ADC Of 12 Precision acquisition channel to collect , According to the resource distribution of the expansion board ：

Program

//ADC -AO
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_4;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_2MHz;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AIN;   
GPIO_Init(GPIOA, &GPIO_InitStructure);	

//ADC -DO
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_3;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IPU;
GPIO_Init(GPIOA, &GPIO_InitStructure);

void ADC_Configuration(void)
{
    
	ADC_InitTypeDef ADC_InitStructure;
	// ADC1  Working mode configuration 
	ADC_InitStructure.ADC_Mode = ADC_Mode_Independent;  
	ADC_InitStructure.ADC_ScanConvMode = DISABLE;
	ADC_InitStructure.ADC_ContinuousConvMode = DISABLE;  // Single conversion   The difference between the two is that continuous conversion does not stop until all data conversion is completed , A single conversion stops when the data is converted only once , The conversion must be triggered again 
	ADC_InitStructure.ADC_ExternalTrigConv = ADC_ExternalTrigConv_None;
	ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right;
	ADC_InitStructure.ADC_NbrOfChannel = 1;
	ADC_Init(ADC1, &ADC_InitStructure);	
	
	ADC_Cmd(ADC1, ENABLE);   
	ADC_ResetCalibration(ADC1);
	/* Check the end of ADC1 reset calibration register */
	while(ADC_GetResetCalibrationStatus(ADC1));
	ADC_StartCalibration(ADC1);
	/* Check the end of ADC1 calibration */
	while(ADC_GetCalibrationStatus(ADC1));	

}

u16 Read_ADC(void)
{
    
	u16 temp;
	ADC_RegularChannelConfig(ADC1, ADC_Channel_4, 1, ADC_SampleTime_1Cycles5);  //ADC_AO Corresponding to the channel 4
	ADC_SoftwareStartConvCmd(ADC1,ENABLE);
    while(ADC_GetFlagStatus(ADC1, ADC_FLAG_EOC) == RESET);
	temp = ADC_GetConversionValue(ADC1);
    ADC_SoftwareStartConvCmd(ADC1,DISABLE);	
	return temp;
}

The main function
1. Digital output port DO: The switching value signal output is the high and low level value output through the comparator after the partial voltage of photosensitive resistance and potentiometer .
2. Analog output port AO: The analog output is the partial voltage value of photosensitive resistance and fixed value resistance

while(1)
{
    		
    temp_AO = Read_ADC();
	sprintf((char *)str,  " R-P:%.1fK ", temp_AO/(4096.-temp_AO)*10);
	LCD_DisplayStringLine(Line6, str);
	if(GPIO_ReadInputDataBit(GPIOA, GPIO_Pin_3) == 1)
	{
    
		LCD_DisplayStringLine(Line7, (u8*)" DO:High ");
	}
	else
	{
    
		LCD_DisplayStringLine(Line7, (u8*)" DO:Low ");
	}

Be careful ：
because RP7 The resistance and of the potentiometer R45 Resistance difference of 500 times , And bright resistance and R46 The resistance of may differ by 1-50 Within times , So we can get the following phenomenon ：
1. When adjusting the potentiometer RP7 bring DO Output hign When ： Let the photoresist encounter strong light , The resistance of Photoforming photoresist decreases ,DO So as to output low （ This jump value is best adjusted RP7 It can just output when the photoresist is normal hign that will do , If the value of the potentiometer is too small , It may be illuminated into a photoresist. After encountering strong light, its resistance value is still greater than that of the potentiometer ）

2. When adjusting the potentiometer RP7 bring DO Output low When : Because the same direction input and reverse input voltage values are relatively large , At this time, the photosensitive resistance may be no matter how large , The voltage of the same direction input terminal is still lower than that of the reverse input terminal , thus DO Output all the time low