17. STM32-I²C EEPROM

上篇针对AT24C256B DataSheet当中的地址以及功能说明，这一篇会使用STM32去对EEPROM做写入与读取。

首先先看一下接线的部分(x :不用接)

照上方的接法地址会变成(1 0 1 0 0 0 0 R/W )，这时就可以知道写入与读取的设备地址拉，分别是0XA0(写入)与0XA1(读取)。

程序

• I2C Start :

void I2C_Start()
{
	HAL_GPIO_WritePin(GPIOB, SCL_Pin, SET);
	HAL_GPIO_WritePin(GPIOB, SDA_Pin, SET);
	HAL_Delay(1);
	HAL_GPIO_WritePin(GPIOB, SDA_Pin, RESET);
	HAL_Delay(1);
	HAL_GPIO_WritePin(GPIOB, SCL_Pin, RESET);
	HAL_Delay(1);
}
}

• I2C Stop :

void I2C_Stop()
{
	HAL_GPIO_WritePin(GPIOB, SDA_Pin, RESET);
	HAL_GPIO_WritePin(GPIOB, SCL_Pin, SET);
	HAL_Delay(1);
	HAL_GPIO_WritePin(GPIOB, SDA_Pin, SET);
}

• I2C_Write

void I2C_WriteByte(unsigned char dat)
{
	unsigned char i = 0;
	for(i=0;i<8;i++)
	{
		//HAL_GPIO_WritePin(GPIOB, SCL_Pin, 0);
		if(dat & 0x80)
			HAL_GPIO_WritePin(GPIOB,SDA_Pin ,1);
		else
			HAL_GPIO_WritePin(GPIOB, SDA_Pin, 0);
		HAL_GPIO_WritePin(GPIOB, SCL_Pin, 1);
		dat<<=1;
		HAL_GPIO_WritePin(GPIOB, SCL_Pin, 0);
	}
	HAL_GPIO_WritePin(GPIOB, SDA_Pin, 0);
	HAL_GPIO_WritePin(GPIOB, SCL_Pin, 0);
	HAL_GPIO_WritePin(GPIOB, SCL_Pin, 1);
	HAL_GPIO_WritePin(GPIOB, SCL_Pin, 0);
}

• I2C_Read

unsigned char I2C_ReadByte(int ACK)
{
	unsigned char dat = 0, i = 0;
	for(i = 0; i < 8; i++)
	{
		HAL_GPIO_WritePin(GPIOB, SCL_Pin, 1);
		dat<<=1;
		if(HAL_GPIO_ReadPin(GPIOC, GPIO_PIN_3)==1)
		{
			dat |= 0x01;
		}
		//HAL_GPIO_WritePin(GPIOB, SCL_Pin, 1);
		HAL_GPIO_WritePin(GPIOB, SCL_Pin, 0);
	}
	if(ACK == 1)
		HAL_GPIO_WritePin(GPIOB, SDA_Pin, 0);
	else
		HAL_GPIO_WritePin(GPIOB, SDA_Pin, 1);
	HAL_GPIO_WritePin(GPIOB, SCL_Pin, SET);
	HAL_GPIO_WritePin(GPIOB, SCL_Pin, RESET);
	HAL_GPIO_WritePin(GPIOB, SDA_Pin, RESET);
	return dat;
}

AT24C256B 函数

• AT24C256_Write

void At24c256_Write(unsigned char Paddr,unsigned char Waddr, unsigned char dat)
{
	I2C_Start();
	I2C_WriteByte(0xA0);
	HAL_Delay(1);
	I2C_WriteByte(Paddr);
	HAL_Delay(1);
	I2C_WriteByte(Waddr);
	HAL_Delay(1);
	I2C_WriteByte(dat);
	HAL_Delay(1);
	I2C_Stop();
}

• AT24C256_Read

unsigned char At24c256_Read(unsigned char Paddr ,unsigned char Addr)
{
	unsigned char dat = 0;
	I2C_Start();
	I2C_WriteByte(0xA0);
	HAL_Delay(1);
	I2C_WriteByte(Paddr);
	HAL_Delay(1);
	I2C_WriteByte(Addr);
	I2C_Start();
	I2C_WriteByte(0xA1);
	HAL_Delay(1);
	dat = I2C_ReadByte(0);
	HAL_Delay(1);
	I2C_Stop();
	return dat;
}

LA分析

手边有LA可以接上去看看I2C是否正确，地址会显示0x50是正常的因为最低位是R/W，实际地址为 1 0 1 0 0 0 0!
可以确定一下在写入每一笔资料时是ACK(也就是SDA = 0)，而读取资料是NACK(也就是SDA = 1)。