（嵌入式）I2C温湿度采集
目录
- 一、硬件I2C和软件I2C
- 二、使用AHT20采集温湿度
-
- 1、实验工具
- 2、实验步骤
-
- （1）、编写代码
- （2）、硬件连接
- （3）、往核心板内烧入程序
- （4）、运行结果
- 三、参考链接
一、硬件I2C和软件I2C
所谓硬件I2C对应芯片上的I2C外设，有相应I2C驱动电路，其所使用的I2C管脚也是专用的；软件baiI2C一般是用GPIO管脚，用软件控制管脚状态以模拟I2C通信波形。
硬件I2C的效率要远高于软件的，而软件I2C由于不受管脚限制，接口比较灵活。
模拟I2C 是通过GPIO，软件模拟寄存器的工作方式，而硬件（固件）I2C是直接调用内部寄存器进行配置。如果要从具体硬件上来看，可以去看下芯片手册。因为固件I2C的端口是固定的，所以会有所区别。
至于如何区分它们
可以看底层配置，比如IO口配置，如果配置了IO口的功能（IIC功能）那就是固件IIC，否则就是模拟
可以看IIC写函数，看里面有木有调用现成的函数或者给某个寄存器赋值，如果有，则肯定是固件IIC功能，没有的话肯定是数据一个bit一个bit模拟发生送的，肯定用到了循环，则为模拟。
根据代码量判断，模拟的代码量肯定比固件的要大。
- 硬件IIC用法比较复杂，模拟IIC的流程更清楚一些。
- 硬件IIC速度比模拟快，并且可以用DMA
- 模拟IIC可以在任何管脚上，而硬件只能在固定管脚上。
软件i2c是程序员使用程序控制SCL,SDA线输出高低电平，模拟i2c协议的时序。一般较硬件i2c稳定，但是程序较为繁琐，但不难。
硬件i2c程序员只要调用i2c的控制函数即可，不用直接的去控制SCL,SDA高低电平的输出。但是有些单片机的硬件i2c不太稳定，调试问题较多。
二、使用AHT20采集温湿度
1、实验工具
（1）、Stm32F10X核心板
（2）、AHT20温湿度传感器
（3）、ST-LINK、USB转TTL
（4）、Keil 5
2、实验步骤
（1）、编写代码
在keil5中打开一个野火的串口通讯例程，然后创建文件写入以下代码
例程：
代码：
delay.h
#ifndef __DELAY_H
#define __DELAY_H
#include "sys.h"
void delay_init(void);
void delay_ms(u16 nms);
void delay_us(u32 nus);
#endif
delay.c
#include "delay.h"
#include "sys.h"
#if SYSTEM_SUPPORT_UCOS
#include "includes.h"
#endif
static u8 fac_us=0;
static u16 fac_ms=0;
#ifdef OS_CRITICAL_METHOD
void SysTick_Handler(void)
{
OSIntEnter();
OSTimeTick();
OSIntExit();
#endif
void delay_init()
{
#ifdef OS_CRITICAL_METHOD
u32 reload;
#endif
SysTick_CLKSourceConfig(SysTick_CLKSource_HCLK_Div8);
fac_us=SystemCoreClock/8000000;
#ifdef OS_CRITICAL_METHOD
reload=SystemCoreClock/8000000;
reload*=1000000/OS_TICKS_PER_SEC;
fac_ms=1000/OS_TICKS_PER_SEC;
SysTick->CTRL|=SysTick_CTRL_TICKINT_Msk;
SysTick->LOAD=reload;
SysTick->CTRL|=SysTick_CTRL_ENABLE_Msk;
#else
fac_ms=(u16)fac_us*1000;
#endif
}
#ifdef OS_CRITICAL_METHOD
void delay_us(u32 nus)
{
u32 ticks;
u32 told,tnow,tcnt=0;
u32 reload=SysTick->LOAD;
ticks=nus*fac_us;
tcnt=0;
told=SysTick->VAL;
while(1)
{
tnow=SysTick->VAL;
if(tnow!=told)
{
if(tnow<told)tcnt+=told-tnow;
else tcnt+=reload-tnow+told;
told=tnow;
if(tcnt>=ticks)break;
}
};
}
void delay_ms(u16 nms)
{
if(OSRunning==TRUE)
{
if(nms>=fac_ms)
{
OSTimeDly(nms/fac_ms);
}
nms%=fac_ms;
}
delay_us((u32)(nms*1000));
}
#else
void delay_us(u32 nus)
{
u32 temp;
SysTick->LOAD=nus*fac_us;
SysTick->VAL=0x00;
SysTick->CTRL|=SysTick_CTRL_ENABLE_Msk ;
do
{
temp=SysTick->CTRL;
}
while(temp&0x01&&!(temp&(1<<16)));
SysTick->CTRL&=~SysTick_CTRL_ENABLE_Msk;
SysTick->VAL =0X00;
}
void delay_ms(u16 nms)
{
u32 temp;
SysTick->LOAD=(u32)nms*fac_ms;
SysTick->VAL =0x00;
SysTick->CTRL|=SysTick_CTRL_ENABLE_Msk ;
do
{
temp=SysTick->CTRL;
}
while(temp&0x01&&!(temp&(1<<16)));
SysTick->CTRL&=~SysTick_CTRL_ENABLE_Msk;
SysTick->VAL =0X00;
}
#endif
sys.h
#ifndef __SYS_H
#define __SYS_H
#include "stm32f10x.h"
//
//STM32F103o?D?°?ày3ì
//?aoˉêy°?±?ày3ì
/********** mcudev.taobao.com 3??· ********/
//
//0,2??§3?ucos
//1,?§3?ucos
#define SYSTEM_SUPPORT_UCOS 0 //?¨ò??μí3???t?Dê?·??§3?UCOS
//??′?2ù×÷,êμ??51àà??μ?GPIO????1|?ü
//??ì?êμ??????,2???<>μú????(87ò3~92ò3).
//IO?ú2ù×÷oê?¨ò?
#define BITBAND(addr, bitnum) ((addr & 0xF0000000)+0x2000000+((addr &0xFFFFF)<<5)+(bitnum<<2))
#define MEM_ADDR(addr) *((volatile unsigned long *)(addr))
#define BIT_ADDR(addr, bitnum) MEM_ADDR(BITBAND(addr, bitnum))
//IO?úμ??·ó3é?
#define GPIOA_ODR_Addr (GPIOA_BASE+12) //0x4001080C
#define GPIOB_ODR_Addr (GPIOB_BASE+12) //0x40010C0C
#define GPIOC_ODR_Addr (GPIOC_BASE+12) //0x4001100C
#define GPIOD_ODR_Addr (GPIOD_BASE+12) //0x4001140C
#define GPIOE_ODR_Addr (GPIOE_BASE+12) //0x4001180C
#define GPIOF_ODR_Addr (GPIOF_BASE+12) //0x40011A0C
#define GPIOG_ODR_Addr (GPIOG_BASE+12) //0x40011E0C
#define GPIOA_IDR_Addr (GPIOA_BASE+8) //0x40010808
#define GPIOB_IDR_Addr (GPIOB_BASE+8) //0x40010C08
#define GPIOC_IDR_Addr (GPIOC_BASE+8) //0x40011008
#define GPIOD_IDR_Addr (GPIOD_BASE+8) //0x40011408
#define GPIOE_IDR_Addr (GPIOE_BASE+8) //0x40011808
#define GPIOF_IDR_Addr (GPIOF_BASE+8) //0x40011A08
#define GPIOG_IDR_Addr (GPIOG_BASE+8) //0x40011E08
//IO?ú2ù×÷,????μ￥ò?μ?IO?ú!
//è·±￡nμ??μD?óú16!
#define PAout(n) BIT_ADDR(GPIOA_ODR_Addr,n) //ê?3?
#define PAin(n) BIT_ADDR(GPIOA_IDR_Addr,n) //ê?è?
#define PBout(n) BIT_ADDR(GPIOB_ODR_Addr,n) //ê?3?
#define PBin(n) BIT_ADDR(GPIOB_IDR_Addr,n) //ê?è?
#define PCout(n) BIT_ADDR(GPIOC_ODR_Addr,n) //ê?3?
#define PCin(n) BIT_ADDR(GPIOC_IDR_Addr,n) //ê?è?
#define PDout(n) BIT_ADDR(GPIOD_ODR_Addr,n) //ê?3?
#define PDin(n) BIT_ADDR(GPIOD_IDR_Addr,n) //ê?è?
#define PEout(n) BIT_ADDR(GPIOE_ODR_Addr,n) //ê?3?
#define PEin(n) BIT_ADDR(GPIOE_IDR_Addr,n) //ê?è?
#define PFout(n) BIT_ADDR(GPIOF_ODR_Addr,n) //ê?3?
#define PFin(n) BIT_ADDR(GPIOF_IDR_Addr,n) //ê?è?
#define PGout(n) BIT_ADDR(GPIOG_ODR_Addr,n) //ê?3?
#define PGin(n) BIT_ADDR(GPIOG_IDR_Addr,n) //ê?è?
void NVIC_Configuration(void);
#endif
sys.c
#include "sys.h"
void NVIC_Configuration(void)
{
NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);
}
usart.h
#ifndef __USART_H
#define __USART_H
#include "stdio.h"
#include "sys.h"
//STM32F103o?D?°?ày3ì
//?aoˉêy°?±?ày3ì
/********** mcudev.taobao.com 3??· ********/
//
//STM32?a·￠°?
//′??ú13?ê??ˉ
#define USART_REC_LEN 200 //?¨ò?×?′ó?óê?×??úêy 200
#define EN_USART1_RX 1 //ê1?ü￡¨1￡?/???1￡¨0￡?′??ú1?óê?
extern u8 USART_RX_BUF[USART_REC_LEN]; //?óê??o3?,×?′óUSART_REC_LEN??×??ú.??×??ú?a??DD·?
extern u16 USART_RX_STA; //?óê?×′ì?±ê??
//è?1???′??ú?D???óê?￡???2?òa×￠êíò???oê?¨ò?
void uart_init(u32 bound);
#endif
usart.c
#include "sys.h"
#include "usart.h"
#if SYSTEM_SUPPORT_UCOS
#include "includes.h"
#endif
#if 1
#pragma import(__use_no_semihosting)
struct __FILE
{
int handle;
};
FILE __stdout;
void _sys_exit(int x)
{
x = x;
}
int fputc2(int ch, FILE *f)
{
while((USART1->SR&0X40)==0){};//?-?··￠?í,?±μ?·￠?ííê±?
USART1->DR = (u8) ch;
return ch;
}
#endif
#if EN_USART1_RX
u8 USART_RX_BUF[USART_REC_LEN];
u16 USART_RX_STA=0;
void uart_init(u32 bound){
GPIO_InitTypeDef GPIO_InitStructure;
USART_InitTypeDef USART_InitStructure;
NVIC_InitTypeDef NVIC_InitStructure;
RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1|RCC_APB2Periph_GPIOA, ENABLE);
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
GPIO_Init(GPIOA, &GPIO_InitStructure);
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
GPIO_Init(GPIOA, &GPIO_InitStructure);
NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority=3 ;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 3;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);
USART_InitStructure.USART_BaudRate = bound;
USART_InitStructure.USART_WordLength = USART_WordLength_8b;
USART_InitStructure.USART_StopBits = USART_StopBits_1;
USART_InitStructure.USART_Parity = USART_Parity_No;
USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;
USART_Init(USART1, &USART_InitStructure);
USART_ITConfig(USART1, USART_IT_RXNE, ENABLE);
USART_Cmd(USART1, ENABLE);
}
void USART1_IRQHandler2(void)
{
u8 Res;
#ifdef OS_TICKS_PER_SEC
OSIntEnter();
#endif
if(USART_GetITStatus(USART1, USART_IT_RXNE) != RESET)
{
Res =USART_ReceiveData(USART1);//(USART1->DR);
if((USART_RX_STA&0x8000)==0)
{
if(USART_RX_STA&0x4000)
{
if(Res!=0x0a)USART_RX_STA=0;
else USART_RX_STA|=0x8000;
}
else
{
if(Res==0x0d)USART_RX_STA|=0x4000;
else
{
USART_RX_BUF[USART_RX_STA&0X3FFF]=Res ;
USART_RX_STA++;
if(USART_RX_STA>(USART_REC_LEN-1))USART_RX_STA=0;
}
}
}
}
#ifdef OS_TICKS_PER_SEC
OSIntExit();
#endif
}
#endif
i2c.h
#ifndef __I2C_H
#define __I2C_H
#include "sys.h"
#include "delay.h"
#include "usart.h"
//ê1ó?IIC1 1ò??M24C02,OLED,LM75AD,HT1382 PB6,PB7
#define SDA_IN() {GPIOB->CRL&=0X0FFFFFFF;GPIOB->CRL|=(u32)8<<28;}
#define SDA_OUT() {GPIOB->CRL&=0X0FFFFFFF;GPIOB->CRL|=(u32)3<<28;}
//IO2ù×÷oˉêy
#define IIC_SCL PBout(6) //SCL
#define IIC_SDA PBout(7) //SDA
#define READ_SDA PBin(7) //ê?è?SDA
//IIC?ùóD2ù×÷oˉêy
void IIC_Init(void); //3?ê??ˉIICμ?IO?ú
void IIC_Start(void); //·￠?íIIC?aê?D?o?
void IIC_Stop(void); //·￠?íIICí￡?1D?o?
void IIC_Send_Byte(u8 txd); //IIC·￠?íò???×??ú
u8 IIC_Read_Byte(unsigned char ack);//IIC?áè?ò???×??ú
u8 IIC_Wait_Ack(void); //IICμè′yACKD?o?
void IIC_Ack(void); //IIC·￠?íACKD?o?
void IIC_NAck(void); //IIC2?·￠?íACKD?o?
void IIC_WriteByte(uint16_t addr,uint8_t data,uint8_t device_addr);
uint16_t IIC_ReadByte(uint16_t addr,uint8_t device_addr,uint8_t ByteNumToRead);//??′??÷μ??·￡??÷?tμ??·￡?òa?áμ?×??úêy
void read_AHT20_once(void);
void reset_AHT20(void);
void init_AHT20(void);
void startMeasure_AHT20(void);
void read_AHT20(void);
uint8_t Receive_ACK(void);
void Send_ACK(void);
void SendNot_Ack(void);
void I2C_WriteByte(uint8_t input);
uint8_t I2C_ReadByte(void);
void set_AHT20sendOutData(void);
void I2C_Start(void);
void I2C_Stop(void);
#endif
i2c.c
#include "i2c.h"
#include "delay.h"
uint8_t ack_status=0;
uint8_t readByte[6];
uint8_t AHT20_status=0;
uint32_t H1=0; //Humility
uint32_t T1=0; //Temperature
uint8_t AHT20_OutData[4];
uint8_t AHT20sendOutData[10] = {0xFA, 0x06, 0x0A, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xFF};
void IIC_Init(void)
{
GPIO_InitTypeDef GPIO_InitStructure;
RCC_APB2PeriphClockCmd( RCC_APB2Periph_GPIOB, ENABLE );
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6|GPIO_Pin_7;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP ; //í?íìê?3?
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOB, &GPIO_InitStructure);
IIC_SCL=1;
IIC_SDA=1;
}
void IIC_Start(void)
{
SDA_OUT();
IIC_SDA=1;
IIC_SCL=1;
delay_us(4);
IIC_SDA=0;//START:when CLK is high,DATA change form high to low
delay_us(4);
IIC_SCL=0;
}
void IIC_Stop(void)
{
SDA_OUT();
IIC_SCL=0;
IIC_SDA=0;//STOP:when CLK is high DATA change form low to high
delay_us(4);
IIC_SCL=1;
IIC_SDA=1;
delay_us(4);
}
u8 IIC_Wait_Ack(void)
{
u8 ucErrTime=0;
SDA_IN();
IIC_SDA=1;delay_us(1);
IIC_SCL=1;delay_us(1);
while(READ_SDA)
{
ucErrTime++;
if(ucErrTime>250)
{
IIC_Stop();
return 1;
}
}
IIC_SCL=0;
return 0;
}
void IIC_Ack(void)
{
IIC_SCL=0;
SDA_OUT();
IIC_SDA=0;
delay_us(2);
IIC_SCL=1;
delay_us(2);
IIC_SCL=0;
}
//2?2úéúACKó|′e
void IIC_NAck(void)
{
IIC_SCL=0;
SDA_OUT();
IIC_SDA=1;
delay_us(2);
IIC_SCL=1;
delay_us(2);
IIC_SCL=0;
}
void IIC_Send_Byte(u8 txd)
{
u8 t;
SDA_OUT();
IIC_SCL=0;
for(t=0;t<8;t++)
{
IIC_SDA=(txd&0x80)>>7;
txd<<=1;
delay_us(2);
IIC_SCL=1;
delay_us(2);
IIC_SCL=0;
delay_us(2);
}
}
u8 IIC_Read_Byte(unsigned char ack)
{
unsigned char i,receive=0;
SDA_IN();
for(i=0;i<8;i++ )
{
IIC_SCL=0;
delay_us(2);
IIC_SCL=1;
receive<<=1;
if(READ_SDA)receive++;
delay_us(1);
}
if (!ack)
IIC_NAck();
else
IIC_Ack();
return receive;
}
void IIC_WriteByte(uint16_t addr,uint8_t data,uint8_t device_addr)
{
IIC_Start();
if(device_addr==0xA0)
IIC_Send_Byte(0xA0 + ((addr/256)<<1));
else
IIC_Send_Byte(device_addr);
IIC_Wait_Ack();
IIC_Send_Byte(addr&0xFF);
IIC_Wait_Ack();
IIC_Send_Byte(data);
IIC_Wait_Ack();
IIC_Stop();
if(device_addr==0xA0)
delay_ms(10);
else
delay_us(2);
}
uint16_t IIC_ReadByte(uint16_t addr,uint8_t device_addr,uint8_t ByteNumToRead)
{
uint16_t data;
IIC_Start();
if(device_addr==0xA0)
IIC_Send_Byte(0xA0 + ((addr/256)<<1));
else
IIC_Send_Byte(device_addr);
IIC_Wait_Ack();
IIC_Send_Byte(addr&0xFF);
IIC_Wait_Ack();
IIC_Start();
IIC_Send_Byte(device_addr+1);
IIC_Wait_Ack();
if(ByteNumToRead == 1)
{
data=IIC_Read_Byte(0);
}
else
{
data=IIC_Read_Byte(1);
data=(data<<8)+IIC_Read_Byte(0);
}
IIC_Stop();//2úéúò???í￡?1ì??t
return data;
}
void read_AHT20_once(void)
{
delay_ms(10);
startMeasure_AHT20();
delay_ms(80);
read_AHT20();
delay_ms(5);
}
void startMeasure_AHT20(void)
{
I2C_Start();
I2C_WriteByte(0x70);
ack_status = Receive_ACK();
if(ack_status);
else printf("7-n-");
I2C_WriteByte(0xAC);
ack_status = Receive_ACK();
if(ack_status);
else printf("8-n-");
I2C_WriteByte(0x33);
ack_status = Receive_ACK();
if(ack_status);
else printf("9-n-");
I2C_WriteByte(0x00);
ack_status = Receive_ACK();
if(ack_status);
else printf("10-n-");
I2C_Stop();
}
void read_AHT20(void)
{
uint8_t i;
for(i=0; i<6; i++)
{
readByte[i]=0;
}
I2C_Start();
I2C_WriteByte(0x71);
ack_status = Receive_ACK();
readByte[0]= I2C_ReadByte();
Send_ACK();
readByte[1]= I2C_ReadByte();
Send_ACK();
readByte[2]= I2C_ReadByte();
Send_ACK();
readByte[3]= I2C_ReadByte();
Send_ACK();
readByte[4]= I2C_ReadByte();
Send_ACK();
readByte[5]= I2C_ReadByte();
SendNot_Ack();
//Send_ACK();
I2C_Stop();
if( (readByte[0] & 0x68) == 0x08 )
{
H1 = readByte[1];
H1 = (H1<<8) | readByte[2];
H1 = (H1<<8) | readByte[3];
H1 = H1>>4;
H1 = (H1*1000)/1024/1024;
T1 = readByte[3];
T1 = T1 & 0x0000000F;
T1 = (T1<<8) | readByte[4];
T1 = (T1<<8) | readByte[5];
T1 = (T1*2000)/1024/1024 - 500;
AHT20_OutData[0] = (H1>>8) & 0x000000FF;
AHT20_OutData[1] = H1 & 0x000000FF;
AHT20_OutData[2] = (T1>>8) & 0x000000FF;
AHT20_OutData[3] = T1 & 0x000000FF;
}
else
{
AHT20_OutData[0] = 0xFF;
AHT20_OutData[1] = 0xFF;
AHT20_OutData[2] = 0xFF;
AHT20_OutData[3] = 0xFF;
printf("失败了");
}
printf("\r\n");
printf("当前温度为: %d%d.%d",T1/100,(T1/10)%10,T1%10);
printf("\r\n");
printf("当前湿度为: %d%d.%d",H1/100,(H1/10)%10,H1%10);
printf("\r\n");
}
uint8_t Receive_ACK(void)
{
uint8_t result=0;
uint8_t cnt=0;
IIC_SCL = 0;
SDA_IN();
delay_us(4);
IIC_SCL = 1;
delay_us(4);
while(READ_SDA && (cnt<100))
{
cnt++;
}
IIC_SCL = 0;
delay_us(4);
if(cnt<100)
{
result=1;
}
return result;
}
void Send_ACK(void)
{
SDA_OUT();
IIC_SCL = 0;
delay_us(4);
IIC_SDA = 0;
delay_us(4);
IIC_SCL = 1;
delay_us(4);
IIC_SCL = 0;
delay_us(4);
SDA_IN();
}
void SendNot_Ack(void)
{
SDA_OUT();
IIC_SCL = 0;
delay_us(4);
IIC_SDA = 1;
delay_us(4);
IIC_SCL = 1;
delay_us(4);
IIC_SCL = 0;
delay_us(4);
IIC_SDA = 0;
delay_us(4);
}
void I2C_WriteByte(uint8_t input)
{
uint8_t i;
SDA_OUT();
for(i=0; i<8; i++)
{
IIC_SCL = 0;
delay_ms(5);
if(input & 0x80)
{
IIC_SDA = 1;
//delaymm(10);
}
else
{
IIC_SDA = 0;
//delaymm(10);
}
IIC_SCL = 1;
delay_ms(5);
input = (input<<1);
}
IIC_SCL = 0;
delay_us(4);
SDA_IN();
delay_us(4);
}
uint8_t I2C_ReadByte(void)
{
uint8_t resultByte=0;
uint8_t i=0, a=0;
IIC_SCL = 0;
SDA_IN();
delay_ms(4);
for(i=0; i<8; i++)
{
IIC_SCL = 1;
delay_ms(3);
a=0;
if(READ_SDA)
{
a=1;
}
else
{
a=0;
}
//resultByte = resultByte | a;
resultByte = (resultByte << 1) | a;
IIC_SCL = 0;
delay_ms(3);
}
SDA_IN();
delay_ms(10);
return resultByte;
}
void set_AHT20sendOutData(void)
{
AHT20sendOutData[3] = AHT20_OutData[0];
AHT20sendOutData[4] = AHT20_OutData[1];
AHT20sendOutData[5] = AHT20_OutData[2];
AHT20sendOutData[6] = AHT20_OutData[3];
}
void I2C_Start(void)
{
SDA_OUT();
IIC_SCL = 1;
delay_ms(4);
IIC_SDA = 1;
delay_ms(4);
IIC_SDA = 0;
delay_ms(4);
IIC_SCL = 0;
delay_ms(4);
}
void I2C_Stop(void)
{
SDA_OUT();
IIC_SDA = 0;
delay_ms(4);
IIC_SCL = 1;
delay_ms(4);
IIC_SDA = 1;
delay_ms(4);
}
（2）、硬件连接
1、核心板与USB转TTL的连接
核心板—— TTL
PA9 ——RXD
PA10 ——TXD
3.3V——3V3
GND——GND
具体参考：
https://blog.csdn.net/qq_36784975/article/details/87860098
2、核心板与ST-LINK的连接
具体参考：
https://blog.csdn.net/qq_44065738/article/details/104247052
（3）、往核心板内烧入程序
选择对应的芯片
（4）、运行结果
三、参考链接
https://blog.csdn.net/hhhhhh277523/article/details/111397514