蓝桥杯嵌入式比赛中,官方在资源数据包给出了I2C的的驱动程序,我们只需要在此基础上应用即可(建议最好搞懂I2C的底层原理)。对于I2C知识点的考察集中在EEPROM部分,这里贴出代码。
1.官方例程I2C.c
/*
程序说明: CT117E嵌入式竞赛板GPIO模拟I2C总线驱动程序
软件环境: Keil uVision 4.10
硬件环境: CT117E嵌入式竞赛板
日 期: 2011-8-9
*/
#include "stm32f10x.h"
/** I2C 总线接口 */
#define I2C_PORT GPIOB
#define SDA_Pin GPIO_Pin_7
#define SCL_Pin GPIO_Pin_6
#define FAILURE 0
#define SUCCESS 1
//配置SDA信号线为输入模式
void SDA_Input_Mode()
{
GPIO_InitTypeDef GPIO_InitStructure;
GPIO_InitStructure.GPIO_Pin = SDA_Pin;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_2MHz;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IPD;
GPIO_Init(I2C_PORT, &GPIO_InitStructure);
}
//配置SDA信号线为输出模式
void SDA_Output_Mode()
{
GPIO_InitTypeDef GPIO_InitStructure;
GPIO_InitStructure.GPIO_Pin = SDA_Pin;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_2MHz;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
GPIO_Init(I2C_PORT, &GPIO_InitStructure);
}
//
void SDA_Output( uint16_t val )
{
if ( val ) {
GPIO_SetBits(I2C_PORT,SDA_Pin);
} else {
GPIO_ResetBits(I2C_PORT,SDA_Pin);
}
}
//
void SCL_Output( uint16_t val )
{
if ( val ) {
GPIO_SetBits(I2C_PORT,SCL_Pin);
} else {
GPIO_ResetBits(I2C_PORT,SCL_Pin);
}
}
//
uint8_t SDA_Input()
{
return GPIO_ReadInputDataBit( I2C_PORT, SDA_Pin);
}
//延时程序
void delay1(unsigned int n)
{
unsigned int i;
for ( i=0;i<n;++i);
}
//I2C总线启动
void I2CStart(void)
{
SDA_Output(1);delay1(500);
SCL_Output(1);delay1(500);
SDA_Output(0);delay1(500);
SCL_Output(0);delay1(500);
}
//I2C总线停止
void I2CStop(void)
{
SCL_Output(0); delay1(500);
SDA_Output(0); delay1(500);
SCL_Output(1); delay1(500);
SDA_Output(1); delay1(500);
}
//等待应答
unsigned char I2CWaitAck(void)
{
unsigned short cErrTime = 5;
SDA_Input_Mode();
delay1(500);
SCL_Output(1);delay1(500);
while(SDA_Input())
{
cErrTime--;
delay1(500);
if (0 == cErrTime)
{
SDA_Output_Mode();
I2CStop();
return FAILURE;
}
}
SDA_Output_Mode();
SCL_Output(0);delay1(500);
return SUCCESS;
}
//发送应答位
void I2CSendAck(void)
{
SDA_Output(0);delay1(500);
delay1(500);
SCL_Output(1); delay1(500);
SCL_Output(0); delay1(500);
}
//
void I2CSendNotAck(void)
{
SDA_Output(1);
delay1(500);
SCL_Output(1); delay1(500);
SCL_Output(0); delay1(500);
}
//通过I2C总线发送一个字节数据
void I2CSendByte(unsigned char cSendByte)
{
unsigned char i = 8;
while (i--)
{
SCL_Output(0);delay1(500);
SDA_Output(cSendByte & 0x80); delay1(500);
cSendByte += cSendByte;
delay1(500);
SCL_Output(1);delay1(500);
}
SCL_Output(0);delay1(500);
}
//从I2C总线接收一个字节数据
unsigned char I2CReceiveByte(void)
{
unsigned char i = 8;
unsigned char cR_Byte = 0;
SDA_Input_Mode();
while (i--)
{
cR_Byte += cR_Byte;
SCL_Output(0);delay1(500);
delay1(500);
SCL_Output(1);delay1(500);
cR_Byte |= SDA_Input();
}
SCL_Output(0);delay1(500);
SDA_Output_Mode();
return cR_Byte;
}
//I2C总线初始化
void i2c_init()
{
GPIO_InitTypeDef GPIO_InitStructure;
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE);
GPIO_InitStructure.GPIO_Pin = SDA_Pin | SCL_Pin;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_2MHz;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP; // **
GPIO_Init(I2C_PORT, &GPIO_InitStructure);
}
2.用户编写程序–读写AT24C02
//需读写AT24C02
void Write_AT24c02(unsigned char add,unsigned char data1)
{
I2CStart();
I2CSendByte(0xa0);
I2CWaitAck();
I2CSendByte(add);
I2CWaitAck();
I2CSendByte(data1);
I2CWaitAck();
I2CStop();
}
unsigned char Read_AT24c02(unsigned char add)
{
unsigned char temp;
I2CStart();
I2CSendByte(0xa0);
I2CWaitAck();
I2CSendByte(add);
I2CWaitAck();
I2CStart();
I2CSendByte(0xa1);
I2CWaitAck();
temp=I2CReceiveByte();
I2CWaitAck();
I2CStop();
return temp;
}
以上就是蓝桥杯省赛考察EEPROM部分。