备考蓝桥杯8——EEPROM读写
目录
看手册时间
关于IIC
附录 IIC代码
看手册时间
我们主要是搞编程，所以，我们一般会非常关心我们如何对EEPROM进行编程。特别的，EEPROM要做读写，首先是看它的IIC设备地址。
有趣的是——我们的EEPROM的IIC地址是根据地址进行选择的，高四位是固定地址，对于低地址，我们的A2A1A0则是选择在哪一篇地址写，一般的我们的比赛不会用到超过1K的ROM，所以，我们往往习惯上默认我们的IIC前七位地址是1010 000，最后一位用于通知我们的IIC设备是读还是写的。
关于IIC
对于IIC一个通信协议，一个经典的步骤就是——
-
主机发送信息：开启通信，发送信息，接受应答，发送信息，接受应答......然后结束通信。
-
主机接受信息：开启通信，发送必要的信息，接受应答......接受信息，不予应答，结束通信
基于这个思路，我们使用官方提供的软IIC来完成代码：
#include "eeprom.h"
#include "i2c.h"
#define EEPROM_WRITE_DEV_ADDR (0xA0)
#define EEPROM_READ_DEV_ADDR (0xA1)
void eeprom_write(uint8_t dev_addr, uint8_t data)
{
I2CStart();
I2CSendByte(EEPROM_WRITE_DEV_ADDR);
I2CWaitAck();
I2CSendByte(dev_addr);
I2CWaitAck();
I2CSendByte(data);
I2CWaitAck();
I2CStop();
HAL_Delay(20); // for i2c delay
}
uint8_t eeprom_read(uint8_t dev_addr)
{
I2CStart();
I2CSendByte(EEPROM_WRITE_DEV_ADDR);
I2CWaitAck();
I2CSendByte(dev_addr);
I2CWaitAck();
I2CStop();
I2CStart();
I2CSendByte(EEPROM_READ_DEV_ADDR);
I2CWaitAck();
uint8_t result = I2CReceiveByte();
I2CSendNotAck();
I2CStop();
return result;
}我们测试一下，读写一个字节：
I2CInit();
eeprom_write(0, 10);
char disp[20];
uint8_t result = eeprom_read(0);
snprintf(disp, 20, "read from: %d", result);
lcd_middledisplay(Line0, disp);
附录 IIC代码
这个代码是官方的赛题会随身给的，这里为了不去下那2.3GB的玩意，直接在下面贴出来给大家参考
i2c.h
#ifndef __I2C_H
#define __I2C_H
#include "main.h"
void I2CStart(void);
void I2CStop(void);
unsigned char I2CWaitAck(void);
void I2CSendAck(void);
void I2CSendNotAck(void);
void I2CSendByte(unsigned char cSendByte);
unsigned char I2CReceiveByte(void);
void I2CInit(void);
#endifi2c.c
#include "i2c.h"
#define DELAY_TIME 20
void SDA_Input_Mode()
{
GPIO_InitTypeDef GPIO_InitStructure = {0};
GPIO_InitStructure.Pin = GPIO_PIN_7;
GPIO_InitStructure.Mode = GPIO_MODE_INPUT;
GPIO_InitStructure.Pull = GPIO_PULLUP;
GPIO_InitStructure.Speed = GPIO_SPEED_FREQ_HIGH;
HAL_GPIO_Init(GPIOB, &GPIO_InitStructure);
}
void SDA_Output_Mode()
{
GPIO_InitTypeDef GPIO_InitStructure = {0};
GPIO_InitStructure.Pin = GPIO_PIN_7;
GPIO_InitStructure.Mode = GPIO_MODE_OUTPUT_OD;
GPIO_InitStructure.Pull = GPIO_NOPULL;
GPIO_InitStructure.Speed = GPIO_SPEED_FREQ_HIGH;
HAL_GPIO_Init(GPIOB, &GPIO_InitStructure);
}
void SDA_Output( uint16_t val )
{
if ( val )
{
GPIOB->BSRR |= GPIO_PIN_7;
}
else
{
GPIOB->BRR |= GPIO_PIN_7;
}
}
void SCL_Output( uint16_t val )
{
if ( val )
{
GPIOB->BSRR |= GPIO_PIN_6;
}
else
{
GPIOB->BRR |= GPIO_PIN_6;
}
}
uint8_t SDA_Input(void)
{
if(HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_7) == GPIO_PIN_SET){
return 1;
}else{
return 0;
}
}
static void delay1(unsigned int n)
{
uint32_t i;
for ( i = 0; i < n; ++i);
}
void I2CStart(void)
{
SDA_Output(1);
delay1(DELAY_TIME);
SCL_Output(1);
delay1(DELAY_TIME);
SDA_Output(0);
delay1(DELAY_TIME);
SCL_Output(0);
delay1(DELAY_TIME);
}
void I2CStop(void)
{
SCL_Output(0);
delay1(DELAY_TIME);
SDA_Output(0);
delay1(DELAY_TIME);
SCL_Output(1);
delay1(DELAY_TIME);
SDA_Output(1);
delay1(DELAY_TIME);
}
unsigned char I2CWaitAck(void)
{
unsigned short cErrTime = 5;
SDA_Input_Mode();
delay1(DELAY_TIME);
SCL_Output(1);
delay1(DELAY_TIME);
while(SDA_Input())
{
cErrTime--;
delay1(DELAY_TIME);
if (0 == cErrTime)
{
SDA_Output_Mode();
I2CStop();
return ERROR;
}
}
SDA_Output_Mode();
SCL_Output(0);
delay1(DELAY_TIME);
return SUCCESS;
}
void I2CSendAck(void)
{
SDA_Output(0);
delay1(DELAY_TIME);
delay1(DELAY_TIME);
SCL_Output(1);
delay1(DELAY_TIME);
SCL_Output(0);
delay1(DELAY_TIME);
}
void I2CSendNotAck(void)
{
SDA_Output(1);
delay1(DELAY_TIME);
delay1(DELAY_TIME);
SCL_Output(1);
delay1(DELAY_TIME);
SCL_Output(0);
delay1(DELAY_TIME);
}
void I2CSendByte(unsigned char cSendByte)
{
unsigned char i = 8;
while (i--)
{
SCL_Output(0);
delay1(DELAY_TIME);
SDA_Output(cSendByte & 0x80);
delay1(DELAY_TIME);
cSendByte += cSendByte;
delay1(DELAY_TIME);
SCL_Output(1);
delay1(DELAY_TIME);
}
SCL_Output(0);
delay1(DELAY_TIME);
}
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(DELAY_TIME);
delay1(DELAY_TIME);
SCL_Output(1);
delay1(DELAY_TIME);
cR_Byte |= SDA_Input();
}
SCL_Output(0);
delay1(DELAY_TIME);
SDA_Output_Mode();
return cR_Byte;
}
void I2CInit(void)
{
GPIO_InitTypeDef GPIO_InitStructure = {0};
GPIO_InitStructure.Pin = GPIO_PIN_7 | GPIO_PIN_6;
GPIO_InitStructure.Mode = GPIO_MODE_OUTPUT_PP;
GPIO_InitStructure.Pull = GPIO_PULLUP;
GPIO_InitStructure.Speed = GPIO_SPEED_FREQ_HIGH;
HAL_GPIO_Init(GPIOB, &GPIO_InitStructure);
}