Stm32-dac Experiment & high frequency DAC output test

1.DAC Basics

majority STM32 The chip will come with it DAC output module （12 Digital input , Voltage output type DAC）

For example, commonly used STM32F103RCT6 （ RAM48K  FLASH 256K）, Chip DAC There are two output channels

This experiment uses a single DAC passageway 1, use 12 Bit right aligned format output .

 STM32F103 Reference manual P185：

DAC The process , Briefly summarized as ： to DAC_DORx Register assignment , then DAC Module processing , after t_setting after , Analog output pin changes   . from STM32F103RCT6 The data book of t_setting The biggest problem is 4us. therefore DAC The fastest conversion speed is ： 1/4μs=250KHz about . meanwhile , This frequency is also far less than the main frequency of the chip 72MHz, Meet the square wave duty cycle modulation -DAC Output requirements .

2. Enable DAC The general steps of

Turn on PORTA The clock .  STM32F103RCT6 Of DAC passageway 1 stay PA4 . So open the pin first A Series clock , The pin mode is set to analog input （ Because it enables DAC After the passage , Corresponding GPIO The pin will automatically contact DAC Connected to the analog output of , Set as input to avoid additional interference - Then you can test whether it is feasible to set the output mode ）

Code：

RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE ); // Can make  PORTA The clock 
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AIN; // Pin configuration   Analog input  

step2： Can make DAC1 The clock of . Check the data book , find DAC Module clock , Call the function in the firmware library to start ：

RCC_APB1PeriphClockCmd(RCC_APB1Periph_DAC, ENABLE );  // Can make  DAC  Channel clock 

step3： Initialize the working mode ：

This time use single channel enable , passageway 1 Output cache off , Trigger response off , Waveform generator （ Triangle 、 square wave ） close . Just the most basic DAC Output , The function called is dac In the firmware library ：

void DAC_Init(uint32_t DAC_Channel, DAC_InitTypeDef* DAC_InitStruct)

The parameters of the function are in the structure DAC_InitType In the definition of ：

typedef struct

{

  uint32_t DAC_Trigger;    // The value here is  DAC_Trigger_None.

  uint32_t DAC_WaveGeneration;     // Whether to use waveform generation   None

  uint32_t DAC_LFSRUnmask_TriangleAmplitude;  // shielding / Amplitude selector , It only takes effect when the waveform occurs 

  uint32_t DAC_OutputBuffer;          // Disable  DAC1  Output cache off 

}DAC_InitTypeDef;

/* Whether trigger function is enabled ： Sometimes you need to press the key to adjust the output voltage . One way is to use external interrupts EXTI9, Another way is to use software trigger . If you will DAC_InitTypeDef.DAC_Trigger Set to DAC_Trigger_None, that , No other trigger source is required , Use it directly DAC_SetChannelxData(), The output voltage can be set . If a software trigger is used , that , Every time I use DAC_SetChannelxData() After modifying the output voltage , You also need to call DAC_SoftwareTriggerCmd(), The purpose is to enable the software to trigger */

step4： passageway 1 Output enable

DAC_Cmd(DAC_Channel_1, ENABLE); // Can make  DAC1

step5： Set up DAC value ：

void DAC_SetChannel1Data(uint32_t DAC_Align, uint16_t Data)

It is also a function in firmware , Source code ：

/**
  * @brief  Set the specified data holding register value for DAC channel1.
  * @param  DAC_Align: Specifies the data alignment for DAC channel1.
  *   This parameter can be one of the following values:
  *     @arg DAC_Align_8b_R: 8bit right data alignment selected
  *     @arg DAC_Align_12b_L: 12bit left data alignment selected
  *     @arg DAC_Align_12b_R: 12bit right data alignment selected
  * @param  Data : Data to be loaded in the selected data holding register.
  * @retval None
  */
void DAC_SetChannel1Data(uint32_t DAC_Align, uint16_t Data)
{  
  __IO uint32_t tmp = 0;
  
  /* Check the parameters */
  assert_param(IS_DAC_ALIGN(DAC_Align));
  assert_param(IS_DAC_DATA(Data));
  
  tmp = (uint32_t)DAC_BASE; 
  tmp += DHR12R1_OFFSET + DAC_Align;

  /* Set the DAC channel1 selected data holding register */
  *(__IO uint32_t *) tmp = Data;
}

First, the first parameter is 12 position D Input or 8 position D（Right or Left） Input

The second parameter is the output value . Note the second parameter value 12 Bit is in 0~4095（2^12-1） 8 Bit in 0~255

Besides , You can also read the channel output value in the software ：DAC_GetDataOutputValue(DAC_Channel_1);

3.DAC initial

#include "dac.h"

//	 
// This procedure originates from ：   
// The punctual atoms @ALIENTEK
//Copyright(C)  Guangzhou Xingyi Electronic Technology Co., Ltd  2009-2019									  
//
//DAC passageway 1 Output initialization 
void Dac1_Init(void)
{
  
	GPIO_InitTypeDef GPIO_InitStructure;
	DAC_InitTypeDef DAC_InitType;

	RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE );	  // Can make PORTA Channel clock 
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_DAC, ENABLE );	  // Can make DAC Channel clock  

	GPIO_InitStructure.GPIO_Pin = GPIO_Pin_4;				 //  port configuration 
 	GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AIN; 		 // Analog input 
 	GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
 	GPIO_Init(GPIOA, &GPIO_InitStructure);
	GPIO_SetBits(GPIOA,GPIO_Pin_4)	;//PA.4  High output 
					
	DAC_InitType.DAC_Trigger=DAC_Trigger_None;	// Don't use the trigger function  TEN1=0
	DAC_InitType.DAC_WaveGeneration=DAC_WaveGeneration_None;// No waveform generation 
	DAC_InitType.DAC_LFSRUnmask_TriangleAmplitude=DAC_LFSRUnmask_Bit0;// shielding 、 Amplitude setting 
	DAC_InitType.DAC_OutputBuffer=DAC_OutputBuffer_Disable ;	//DAC1 Output cache off  BOFF1=1
  DAC_Init(DAC_Channel_1,&DAC_InitType);	 // initialization DAC passageway 1

	DAC_Cmd(DAC_Channel_1, ENABLE);  // Can make DAC1
  
  DAC_SetChannel1Data(DAC_Align_12b_R, 0);  //12 Bit right alignment data format setting DAC value 

}

// Set up channels 1 Output voltage 
//vol:0~3300, representative 0~3.3V
void Dac1_Set_Vol(u16 vol)
{
	float temp=vol;
	temp/=1000;
	temp=temp*4096/3.3;
	DAC_SetChannel1Data(DAC_Align_12b_R,temp);//12 Bit right alignment data format setting DAC value 
}

initial Function is to encapsulate the above steps .

void Dac1_Set_Vol(u16 vol) Function support float Voltage conversion , Otherwise, every time you call DAC_SetChannel1Data() Time has to be converted .

4.DAC High frequency experiment

Measure in the main function DAC The highest frequency of , And then in LCD On reality . First, use one up-down loop , Give Way DAC The output keeps changing , Then change every time Fre++ . Clear the timer once per second Fre, And then record the highest Fre, That is to say DAC Highest frequency .

#include "led.h"
#include "delay.h"
#include "sys.h"
#include "usart.h"
#include "lcd.h"
#include "adc.h"
#include "dac.h"
#include "timer.h"



u32 Fre=0; //extern  Variables are defined as global variables 
u16 adcx;
float temp;
u8 dvup=1;	

u32 HighestFre=0;
u16 dacval=0;
	
   	
 int main(void)
 { 

	 
	 
	NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);//  Set interrupt priority group 2
	delay_init();	    	 // Delay function initialization 	  
	uart_init(9600);	 	// The serial port is initialized to 9600
	LED_Init();		  		// Initialization and LED Connected hardware interface 
 	LCD_Init();			   	// initialization LCD 				 	
 	Adc_Init();		  		//ADC initialization 
	Dac1_Init();		 	//DAC passageway 1 initialization 	
	TIM3_Int_Init(9999,7199);//10Khz The counting frequency of , Count to 10000 by 1000ms  
	 
 
	POINT_COLOR=RED;// Set the font to red  
	LCD_ShowString(60,50,200,16,16,"Mini STM32");	
	LCD_ShowString(60,70,200,16,16,"DAC TEST");	
	LCD_ShowString(60,90,200,16,16,"2020/6/30");	
	LCD_ShowString(60,120,200,16,16,"HF:");	
	// Display prompt message 											      
	POINT_COLOR=BLUE;// Set the font to blue 
	LCD_ShowString(60,150,200,16,16,"DAC VAL:");	      
	LCD_ShowString(60,170,200,16,16,"DAC VOL:0.000V");	      
	LCD_ShowString(60,190,200,16,16,"ADC VOL:0.000V");	   
	
	DAC_SetChannel1Data(DAC_Align_12b_R, 0);// Set up DAC1 passageway  12 position R For its , Output 0    
	
	while(1)
	{
		
		if(dvup){
			if(dacval<4000)  dacval+=20;
			else dvup=0;
		}
		else{
			if(dacval>200)  dacval-=20;
			else dvup=1;
		}
		
		DAC_SetChannel1Data(DAC_Align_12b_R, dacval);//DAC Output 
		Fre++;


	}										    
}	

Set refresh in timer interrupt LCD,main Update the program as soon as possible DAC frequency .

Timer timer.c Medium IRQHandler:

extern u32 Fre;
extern u16 adcx;
extern float temp;
extern u8 dvup;	
extern u32 HighestFre;
extern u16 dacval;
u32 tempu32;


void TIM3_IRQHandler(void)   //TIM3 interrupt 
{
	if (TIM_GetITStatus(TIM3, TIM_IT_Update) != RESET) // Check the specified TIM Whether the interruption occurs or not :TIM  Interrupt source  
		{
		TIM_ClearITPendingBit(TIM3, TIM_IT_Update  );  // eliminate TIMx Interrupt pending bit of :TIM  Interrupt source 
		
		if(Fre>HighestFre) HighestFre=Fre;
		tempu32=HighestFre;	
		LCD_ShowxNum(100,120,tempu32,8,16,0); // Show highest frequency

		
		adcx=DAC_GetDataOutputValue(DAC_Channel_1);//DAC
		LCD_ShowxNum(124,150,adcx,4,16,0);     	// Show DAC Register values 
		temp=(float)adcx*(3.3/4096);			// obtain DAC Voltage value 
		adcx=temp;
		LCD_ShowxNum(124,170,temp,1,16,0);     	// Display the integral part of the voltage value 
		temp-=adcx;
		temp*=1000;
		LCD_ShowxNum(140,170,temp,3,16,0X80); 	// Display the decimal part of the voltage value 
		adcx=Get_Adc_Average(ADC_Channel_1,10);		// obtain ADC Conversion value 	  
		temp=(float)adcx*(3.3/4096);			// obtain ADC Voltage value 
		adcx=temp;
		LCD_ShowxNum(124,190,temp,1,16,0);     	// Display the integral part of the voltage value 
		temp-=adcx;
		temp*=1000;
		LCD_ShowxNum(140,190,temp,3,16,0X80); 	// Display the decimal part of the voltage value 
		
		LED0=!LED0;	   
			
		Fre=0;
		}
}

4. experimental result

CPU It's basically going on DAC operation . And estimated 250kHz In an order of magnitude , But it will be higher , Maybe the timer is not accurate enough , as well as Tsetting It will be shorter than the mark .

When the main program circulates , The main time consuming is DAC link ：

    while(1)
    {
        if(dvup){
            if(dacval<4000)  dacval+=20;
            else dvup=0;
        }
        else{
            if(dacval>200)  dacval-=20;
            else dvup=1;
        }
        DAC_SetChannel1Data(DAC_Align_12b_R, dacval);//DAC Output
        Fre++;
    }

  Try to modify the source code ：

/**
  * @brief  Set the specified data holding register value for DAC channel1.
  * @param  DAC_Align: Specifies the data alignment for DAC channel1.
  *   This parameter can be one of the following values:
  *     @arg DAC_Align_8b_R: 8bit right data alignment selected
  *     @arg DAC_Align_12b_L: 12bit left data alignment selected
  *     @arg DAC_Align_12b_R: 12bit right data alignment selected
  * @param  Data : Data to be loaded in the selected data holding register.
  * @retval None
  */
void DAC_SetChannel1Data(uint32_t DAC_Align, uint16_t Data)
{  
  __IO uint32_t tmp = 0;
  
  /* Check the parameters */
  //assert_param(IS_DAC_ALIGN(DAC_Align));
  //assert_param(IS_DAC_DATA(Data));
  
  tmp = (uint32_t)DAC_BASE; 
  tmp += DHR12R1_OFFSET + DAC_Align;

  /* Set the DAC channel1 selected data holding register */
  *(__IO uint32_t *) tmp = Data;
}

When modifying, put two lines assert_param The comments , Skipped the parameter check . The highest frequency has hardly increased . explain CPU Computation is not a major time-consuming project .

Put... In the main program DAC_SetChannel1Data The comments , Measured without DAC The highest frequency of other parts of the link ：

1111kHz, It shows that other calculation steps in the cycle take about 0.9us.

Join in DAC It takes about 1/630kHz=1.6us.

  So do it once DAC It takes about 0.7us. This value is higher than that given in the reference manual Tsetting Many small , But here's the thing DAC_SetChannel1Data There seems to be no ACK link , That is, no detection DAC Has it been completed . So further DAC High frequency limit test can be used DAC Square wave output + Test with oscilloscope .