Programming implementation of I2C communication protocol

  Code implementation at24c02 Between master device and slave device I2C data communication

（at24c02 Equipment schematic information is being shared stm32 In the data ）

The idea of code editing is to realize the start signal , End signal , Send slave address and write signal , Send the on-chip address , Send written data , Encapsulate these steps into code functions , Call .

#include <stm32f4xx.h>
#include <iic.h>
#include <delay.h>
#include <stdio.h>



void ic_init(void)
{	
    // Clock initialization structure 
    GPIO_InitTypeDef GPIO_InitStruct;
	
	//1. Turn on GPIOB The clock of 
	RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB,ENABLE);
	
	//2.GPIO initialization  PB8 PB9 Pin 
	GPIO_InitStruct.GPIO_Mode = GPIO_Mode_OUT; // The output mode 
	GPIO_InitStruct.GPIO_OType = GPIO_OType_PP;// Push pull output 
	GPIO_InitStruct.GPIO_Speed = GPIO_Speed_50MHz;// High speed 
	GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_NOPULL;// No up and down 
	GPIO_InitStruct.GPIO_Pin = GPIO_Pin_8|GPIO_Pin_9;// Pin for 9 and 10
	GPIO_Init(GPIOB,&GPIO_InitStruct);
}	

// Set the serial data line SDA Transmission direction （ Two-way communication ）, Mode of incoming pin 
void set_sda_io(GPIOMode_TypeDef IO)
{
	
    GPIO_InitTypeDef GPIO_InitStruct;
	
	//2.GPIO initialization  PB9
	GPIO_InitStruct.GPIO_Mode = IO;
	GPIO_InitStruct.GPIO_OType = GPIO_OType_PP;// Push pull output 
	GPIO_InitStruct.GPIO_Speed = GPIO_Speed_50MHz;// High speed 
	GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_NOPULL;// No up and down 
	GPIO_InitStruct.GPIO_Pin = GPIO_Pin_9;// Pin for 9 Pin No 
	GPIO_Init(GPIOB,&GPIO_InitStruct);
}



// Start signal 
void iic_start(void)
{
	// Set the serial data bus SDA The output mode 
	set_sda_io(GPIO_Mode_OUT);
	
	// Both buses are idle , The default is high 
	SCL = 1;      // Clock bus high 
	SDA_OUT = 1;  // Data bus low level 
	delay_us(5);
	
	// Serial data bus SDA Pull it down 
	SDA_OUT = 0;
	delay_us(5);
	
	//SDA After pulling down , Lower the clock bus SCL, Clamp the bus 
	SCL = 0;
}



// Stop signal 
void iic_stop(void)
{
	// Serial data bus SDA The output mode 
	set_sda_io(GPIO_Mode_OUT);
	
	
    // Serial data bus and clock bus are low level 
    SCL = 0;
	SDA_OUT = 0;
	delay_us(5);
	
	// Serial clock bus SCL pull up 
	SCL = 1;
	delay_us(5);
	
	// Pull up the serial data bus SDA, here SCL and SDA All of them are high , The bus is idle 
	SDA_OUT = 1;
}



// Wait for the slave device to answer , return 0 Indicates a valid response , return 1 Indicates an invalid response 
u8 iic_wait_ack(void)
{
	u8 ack = 0;
	
	// Serial data bus SDA The input mode , Receive response 
	set_sda_io(GPIO_Mode_IN);
	
	// Pull up the serial clock bus SCL, Allow operation from the device SDA
	SCL = 1;
	delay_us(5);
	
	// Read serial data bus SDA level 
	if(SDA_IN){
		ack = 1;// Invalid response 
		iic_stop();// Invalid response received , Stop communication immediately 
	}
	else{
		ack = 0;
	}
	
	SCL = 0;
	delay_us(5);
	
	return ack;
}


// Generate a response signal , The ginseng ack=0 Effective response ,ack=1 Invalid response 
void iic_ack(u8 ack)
{
	// Set the serial data bus SDA The output mode 
	set_sda_io(GPIO_Mode_OUT);
	
	// Pull down the clock line , Prepare to modify the data line level 
	SCL = 0;
	delay_us(5);
	
	// Set the serial data bus SDA level 
	if(ack){
		SDA_OUT = 1;
	}
	else{
		SDA_OUT = 0;// Effective response 
	}
	
	delay_us(5);
	
	// After the data is stable, pull up the clock line to let the slave device receive ack
	SCL = 1;
	delay_us(5);
	
	SCL = 0;
}

// send out 1 Bytes of data  ---------  High and low 
void iic_send_byte(u8 txd)
{
	u8 i;
	
	// Set the data serial bus SDA The output mode 
	set_sda_io(GPIO_Mode_OUT);
	
	SCL = 0;
	delay_us(5);
	
	// Send each bit at a time from high to low 
    // Judge txd Is it high or low , It only needs &（ And operation ） On  1<<(7-i) You can judge 
    //1<<（7-i）  It's actually  1 Move left 7 position , Students who are not clear should review bit operations well 
	for(i=0;i<8;i++){
		if(txd&1<<(7-i)){
			SDA_OUT = 1;
		}
		else{
			SDA_OUT = 0;
		}
		delay_us(5);
		
		// Pull up the clock line bus , Let's read this bit from the device 
		SCL = 1;
		delay_us(5);
		// Pull down the clock line , Ready to send next 
		SCL = 0;
	}
}

// receive 1 Bytes of data 
u8 iic_recv_byte(void)
{
	u8 rxd = 0,i;
	
	// Set the serial clock bus SDA The input mode 
	set_sda_io(GPIO_Mode_IN);
	
	SCL = 0;
	
	// Receive each bit from high to low 
	for(i=0;i<8;i++){
		
     // Wait for the other party to set the level 
		delay_us(5);

	// Read during high level 1 Bit data 
		SCL = 1;
		if(SDA_IN)
			rxd |= 1<<(7-i);
		
		// Ready to receive the next 
		delay_us(5);
		SCL = 0;
	}
	
	return rxd;
}

//at24c02 Write 1 Bytes of data 
void at24c02_write_byte(u8 addr,u8 data)
{
	u8 ack;
	
	// Start signal 
	iic_start();
	
	// Send slave address + Write the signal   0x50<<1 | 0 = 0xa0
    // Slave device address （0x50） Move left 1 position   Or operations  0
	iic_send_byte(0xa0);

	// wait for ACK
	ack = iic_wait_ack();
	if(ack){
		printf("ack failed 1\r\n");
		return ;
	}
	
	// Send the written on-chip address 
	iic_send_byte(addr);
	// wait for ACK
	ack = iic_wait_ack();
	if(ack){
		printf("ack failed 2\r\n");
		return ;
	}
	
	// Send written data 
	iic_send_byte(data);
	// wait for ACK
	ack = iic_wait_ack();
	if(ack){
		printf("ack failed 3\r\n");
		return ;
	}
	
	// Stop signal 
	iic_stop();
}

//at24c02 Write 1 Page data 
void at24c02_write_page(u8 addr,u8 *data,u8 len)
{
	u8 ack;
	
	// Start signal 
	iic_start();
	
	// Send slave address + Write the signal   0x50<<1 | 0 = 0xa0
	iic_send_byte(0xa0);
	// wait for ACK
	ack = iic_wait_ack();
	if(ack){
		printf("ack failed 1\r\n");
		return ;
	}
	
	// Send the written on-chip address 
	iic_send_byte(addr);
	// wait for ACK
	ack = iic_wait_ack();
	if(ack){
		printf("ack failed 2\r\n");
		return ;
	}
	
	// Send written data 
	while(len--){
		iic_send_byte(*data++);
		// wait for ACK
		ack = iic_wait_ack();
		if(ack){
			printf("ack failed 3\r\n");
			return ;
		}
	}
	
	// Stop signal 
	iic_stop();
}

//at24c02 read 1 byte 
u8 at24c02_read_byte(u8 addr)
{
	u8 ack,data;
	
	// Start signal 
	iic_start();
	
	// Send slave address + Write the signal   0x50<<1 | 0 = 0xa0
	iic_send_byte(0xa0);
	// wait for ACK
	ack = iic_wait_ack();
	if(ack){
		printf("ack failed 1\r\n");
		return 0;
	}
	
	// Send read on-chip address 
	iic_send_byte(addr);
	// wait for ACK
	ack = iic_wait_ack();
	if(ack){
		printf("ack failed 2\r\n");
		return 0;
	}
	
	// Start signal 
	iic_start();
	
	// Send slave address + Read the signal   0x50<<1 | 1 = 0xa1
	iic_send_byte(0xa1);
	// wait for ACK
	ack = iic_wait_ack();
	if(ack){
		printf("ack failed 3\r\n");
		return 0;
	}
	
	// Receive read 1 Bytes of data 
	data = iic_recv_byte();
	// Invalid response 
	iic_ack(1);
	
	// Stop signal 
	iic_stop();
	
	return data;
}

//at24c02 Read continuously 
void at24c02_seq_read(u8 addr,u8 *data,u8 len)
{
	u8 ack;
	
	// Start signal 
	iic_start();
	
	// Send slave address + Write the signal   0x50<<1 | 0 = 0xa0
	iic_send_byte(0xa0);
	// wait for ACK
	ack = iic_wait_ack();
	if(ack){
		printf("ack failed 1\r\n");
		return;
	}
	
	// Send read on-chip address 
	iic_send_byte(addr);
	// wait for ACK
	ack = iic_wait_ack();
	if(ack){
		printf("ack failed 2\r\n");
		return;
	}
	
	// Start signal 
	iic_start();
	
	// Send slave address + Read the signal   0x50<<1 | 1 = 0xa1
	iic_send_byte(0xa1);
	// wait for ACK
	ack = iic_wait_ack();
	if(ack){
		printf("ack failed 3\r\n");
		return;
	}
	
	// Reading data 
	while(len--){
		// Receive read data 
		*data++ = iic_recv_byte();
		
		if(len>0){
			// Effective response 
			iic_ack(0);
		}
		else{
			iic_ack(1);
		}
		
	}
	
	// Stop signal 
	iic_stop();
}