51 single chip microcomputer learning record (VI) IIC, ADC part

51 SCM is almost like this , The relevant code can be seen in my gitee, It can reduce the pain of making your own wheels ：51 SCM learning records

1、iic part

About IIC Principle , It helps to understand , Yes. iic What is not clear can be seen ：

stm32 Configuration summary -iic Use
Summary of the communication protocol frequently asked in the interview

Here, the development board is also connected with one AT24C02 To be used as IIC experiment , This chip is used to do iic Learning is still very classic

This was written before stm32 Related articles ：stm32 Configuration summary -iic Use , You can check it if you need it .

here 51 MCU has no hardware iic, We need to write our own software iic, Here we directly refer to the routine of Puzhong technology ：

#include "iic.h"



void iic_start(void)
{
    
    IIC_SDA = 1; 
    delay_10us(1);
    IIC_SCL = 1;
    delay_10us(1);
    IIC_SDA = 0; // When SCL For high voltage ,SDA From high to low 
    delay_10us(1);
    IIC_SCL = 0; // Hold on I2C Bus , Ready to send or receive data 
    delay_10us(1);
}

void iic_stop(void)
{
    
    IIC_SDA = 0; 
    delay_10us(1);
    IIC_SCL = 1;
    delay_10us(1);
    IIC_SDA = 1; // When SCL For high voltage ,SDA From low to high 
    delay_10us(1);
}

void iic_ack(void)
{
    
    IIC_SCL = 0;
    IIC_SDA = 0; // SDA Low level 
    delay_10us(1);
    IIC_SCL = 1;
    delay_10us(1);
    IIC_SCL = 0;
}

void iic_nack(void)
{
    
    IIC_SCL = 0;
    IIC_SDA = 1; // SDA High level 
    delay_10us(1);
    IIC_SCL = 1;
    delay_10us(1);
    IIC_SCL = 0;
}

u8 iic_wait_ack(void)
{
    
    u8 time_temp = 0;

    IIC_SCL = 1;
    delay_10us(1);
    while (IIC_SDA) // wait for SDA Low level 
    {
    
        time_temp++;
        if (time_temp > 100) // If the timeout occurs, it will be forced to end IIC signal communication 
        {
    
            iic_stop();
            return 1;
        }
    }
    IIC_SCL = 0;
    return 0;
}

void iic_write_byte(u8 dat)
{
    
    u8 i = 0;

    IIC_SCL = 0;
    for (i = 0; i < 8; i++) // loop 8 One byte at a time , Pass high and then low 
    {
    
        if ((dat & 0x80) > 0)
            IIC_SDA = 1;
        else
            IIC_SDA = 0;
        dat <<= 1;
        delay_10us(1);
        IIC_SCL = 1;
        delay_10us(1);
        IIC_SCL = 0;
        delay_10us(1);
    }
}

u8 iic_read_byte(u8 ack)
{
    
    u8 i = 0, receive = 0;

    for (i = 0; i < 8; i++) // loop 8 Read one byte at a time , Read high and then pass low 
    {
    
        IIC_SCL = 0;
        delay_10us(1);
        IIC_SCL = 1;
        receive <<= 1;
        if (IIC_SDA)
            receive++;
        delay_10us(1);
    }
    if (!ack)
        iic_nack();
    else
        iic_ack();

    return receive;
}

Reading and writing at24c02 Part of it is also ：

#include "at24c02.h"

void at24c02_write_one_byte(u8 addr,u8 dat)
{
    				   	  	    																 
    iic_start();  
	iic_write_byte(0XA0);	// Send write command  
	iic_wait_ack();	   
    iic_write_byte(addr);	// Send write address  
	iic_wait_ack(); 	 										  		   
	iic_write_byte(dat);	// Send byte  
	iic_wait_ack();  		    	   
    iic_stop();				// Create a stop condition 
	delay_ms(10);	 
}

u8 at24c02_read_one_byte(u8 addr)
{
    				  
	u8 temp=0;		  	    																 
    iic_start();  
	iic_write_byte(0XA0);	// Send write command  
	iic_wait_ack(); 
    iic_write_byte(addr); 	// Send write address  
	iic_wait_ack();	    
	iic_start();  	 	   
	iic_write_byte(0XA1); 	// Enter receive mode  
	iic_wait_ack();	 
    temp=iic_read_byte(0);	// Read byte  
    iic_stop();				// Create a stop condition  
	return temp;			// Return the read data 
}

In this way, you can read and write in the main function .

2、ADC part

here 51 There seems to be no SCM ADC On chip peripherals , So we need something else AD Module to realize the corresponding functions , It's used here XPT2046 This chip is used to realize , Let's take a look at how this chip realizes its corresponding functions ：

It can be seen that this chip was originally used as a touch screen chip , It's a 12 Bit AD, Monitoring range 0 To 6V. The following is a description of the relevant pins ：

The operating mode is described as follows ：

Selection of single ended mode and differential mode ：（ADC Just direct single ended mode ）

Use IIC And so on , The sequence diagram is as follows ：

The explanation is as follows ：

The command description of the control word is as follows ：

The final code is as follows ：

#include "adc.h"
#include "intrins.h"

void xpt2046_wirte_data(u8 dat)
{
    
    u8 i;

    CLK = 0;
    _nop_();
    for (i = 0; i < 8; i++) // loop 8 Time , Transmit one bit at a time , One byte in total 
    {
    
        DIN = dat >> 7; // Pass high and then low 
        dat <<= 1;      // Move low to high 
        CLK = 0;        // CLK From low to high produces a rising edge , To write data 
        _nop_();
        CLK = 1;
        _nop_();
    }
}

u16 xpt2046_read_data(void)
{
    
    u8 i;
    u16 dat = 0;

    CLK = 0;
    _nop_();
    for (i = 0; i < 12; i++) // loop 12 Time , Read one bit at a time , Greater than one byte , So the return value type is u16
    {
    
        dat <<= 1;
        CLK = 1;
        _nop_();
        CLK = 0; // CLK A falling edge is produced from high to low , To read the data 
        _nop_();
        dat |= DOUT; // Read the high bit first , Reread low order .
    }
    return dat;
}

u16 xpt2046_read_adc_value(u8 cmd)
{
    
    u8 i;
    u16 adc_value = 0;

    CLK = 0;                 // Turn down the clock first 
    CS = 0;                  // Can make XPT2046
    xpt2046_wirte_data(cmd); // Send command word 
    for (i = 6; i > 0; i--)
        ; // Delay waiting for conversion results 
    CLK = 1;
    _nop_();
    CLK = 0; // Send a clock , eliminate BUSY
    _nop_();
    adc_value = xpt2046_read_data();
    CS = 1; // close XPT2046
    return adc_value;
}

3、DAC part

here DAC It's through PWM Combined with the circuit , I've already introduced ADC Related content , I won't repeat it here ,ADC The working principle of is as follows

The circuits used are as follows , Here we want to realize ADC The function of , As long as the output corresponds to PWM that will do .