Article Directory
foreword
- Hardware: stm32f103c8t6 core board
- Software: STM32CubeMX 6.4.0
- Software: keil5 mdk
- Software: Wildfire serial debugging assistant
1. I2C protocol
1. Application
The I2C communication protocol (Inter-Integrated Circuit) was developed by Philps. Because it has few pins, simple hardware implementation, and strong scalability, it does not require external transceiver devices such as USART and CAN. It is now widely used
in Communication between multiple integrated circuits (ICs) in a system.
2. Composition
The most basic is to divide it into physical layer and protocol layer .
The physical layer stipulates the characteristics of mechanical and electronic functional parts in the communication system to ensure the transmission of original data on physical media.
The protocol layer mainly stipulates the communication logic, and unifies the data packaging and unpacking standards of the sending and receiving parties. Simply put, the physical layer stipulates whether we communicate with our mouth or body , and the protocol layer stipulates whether we communicate in Chinese or English .
- A common connection method between I2C communication devices
- Physical layer
I2C is a bus that supports devices. Can connect multiple I2C communication devices, support multiple communication hosts and multiple communication slaves. For the I2C bus, only two bus lines are used, a bidirectional serial data line (SDA) and a serial clock line (SCL).
- Protocol layer
I2C protocol defines communication start and stop signals, data validity, response, arbitration, clock synchronization and address broadcasting.
- I2C architecture of STM32:
- The start and end of the communication:
The SDA line toggles from high to low while the SCL line is high, a condition that indicates the start of communication . When SCL is high level, the SDA line switches from low level to high level, indicating the stop of communication . Start and stop signals are generally generated by the host.
- data availability
The SDA data line transfers one bit of data every clock cycle of SCL. During transmission, the data represented by SDA is valid when SCL is high level , that is, when SDA is high level, it means data "1", and when it is low level, it means data "0". When SCL is low level, the data of SDA is invalid. Generally, at this time, SDA performs level switching to prepare for the next data representation.
- response
I2C data and address transfers come with responses. The response includes two signals of " acknowledgement (ACK)" and "non-acknowledgement (NACK)" . As a data receiver, when the device (regardless of master and slave) receives a byte of data or address transmitted by I2C, if you want the other party to continue sending data, you need to send an "acknowledgment (ACK)" signal to the other party, and the sender will continue to send The next data; if the receiving end wants to end the data transmission, it will send a "non-acknowledgement (NACK)" signal to the other party. After receiving the signal, the sender will generate a stop signal to end the signal transmission.
3. Software I2C and hardware I2C
3.1 Software I2C
The method of controlling the GPIO pin level to generate communication timing through the CPU controlling the pin state at each moment is called software I2C.
3.2 Hardware I2C
The I2C on-chip peripheral of STM32 is responsible for implementing the I2C communication protocol. As long as the peripheral is configured, it will automatically generate communication signals according to the protocol requirements, send and receive data and cache them. The CPU only needs to detect the status of the peripheral and access the data register. The data sending and receiving can be completed. This way of sending and receiving data through peripherals is called hardware I2C.
- difference
Hardware I2C directly uses peripherals to control pins, which can reduce the burden on the CPU. However, when using hardware I2C, some fixed pins must be used as SCL and SDA, while software analog I2C can use any GPIO pin, which is relatively flexible. The usage of hardware I2C is more complicated, and the process of software I2C is clearer. If you want to understand the I2C protocol in detail, using software I2C may better understand the process. In the process of using I2C, hardware I2C may communicate faster and more stable.
2. Collect AHT20 data through hardware I2C protocol
1. Configuration items
By default you have created a new project
- Clock RCC configuration, select HSE as external crystal oscillator mode
- SYS settings, select the Serial Wire mode.
- set USART
- set enable interrupt
- I2C settings
- set DMA mode
- RCC clock
Set the project path, project name, and finally export the file. Use keil to open and write.
2. Configuration code
- Create a new folder and place two files in it:
AHT20-21_DEMO_V1_3.c and AHT20-21_DEMO_V1_3.h
Then create a project folder through the small square, add the two files just now, and need to modify it later.
- Import file path
Copy the previously created folder path
Set file path
Put the file path just now in the last step 2, and then click OK to return.
-
Because the prntf function is rewritten later, you need to check the allow micro-library.
-
Modify the AHT20-21_DEMO_V1_3.h file
#ifndef _AHT20_DEMO_
#define _AHT20_DEMO_
#include "main.h"
void Delay_N10us(uint32_t t);//延时函数
void SensorDelay_us(uint32_t t);//延时函数
void Delay_4us(void); //延时函数
void Delay_5us(void); //延时函数
void Delay_1ms(uint32_t t);
void AHT20_Clock_Init(void); //延时函数
void SDA_Pin_Output_High(void) ; //将PB15配置为输出 ， 并设置为高电平， PB15作为I2C的SDA
void SDA_Pin_Output_Low(void); //将P15配置为输出 并设置为低电平
void SDA_Pin_IN_FLOATING(void); //SDA配置为浮空输入
void SCL_Pin_Output_High(void); //SCL输出高电平，P14作为I2C的SCL
void SCL_Pin_Output_Low(void); //SCL输出低电平
void Init_I2C_Sensor_Port(void); //初始化I2C接口,输出为高电平
void I2C_Start(void); //I2C主机发送START信号
void AHT20_WR_Byte(uint8_t Byte); //往AHT20写一个字节
uint8_t AHT20_RD_Byte(void);//从AHT20读取一个字节
uint8_t Receive_ACK(void); //看AHT20是否有回复ACK
void Send_ACK(void) ; //主机回复ACK信号
void Send_NOT_ACK(void); //主机不回复ACK
void Stop_I2C(void); //一条协议结束
uint8_t AHT20_Read_Status(void);//读取AHT20的状态寄存器
uint8_t AHT20_Read_Cal_Enable(void); //查询cal enable位有没有使能
void AHT20_SendAC(void); //向AHT20发送AC命令
uint8_t Calc_CRC8(uint8_t *message,uint8_t Num);
void AHT20_Read_CTdata(uint32_t *ct); //没有CRC校验，直接读取AHT20的温度和湿度数据
void AHT20_Read_CTdata_crc(uint32_t *ct); //CRC校验后，读取AHT20的温度和湿度数据
void AHT20_Init(void); //初始化AHT20
void JH_Reset_REG(uint8_t addr);///重置寄存器
void AHT20_Start_Init(void);///上电初始化进入正常测量状态
#endif
- Modify AHT20-21_DEMO_V1_3.c file
/*******************************************/
/*@版权所有：广州奥松电子有限公司 */
/*@作者：温湿度传感器事业部 */
/*@版本：V1.2 */
/*******************************************/
//#include "main.h"
#include "AHT20-21_DEMO_V1_3.h"
#include "gpio.h"
#include "i2c.h"
void Delay_N10us(uint32_t t)//延时函数
{
uint32_t k;
while(t--)
{
for (k = 0; k < 2; k++);//110
}
}
void SensorDelay_us(uint32_t t)//延时函数
{
for(t = t-2; t>0; t--)
{
Delay_N10us(1);
}
}
void Delay_4us(void) //延时函数
{
Delay_N10us(1);
Delay_N10us(1);
Delay_N10us(1);
Delay_N10us(1);
}
void Delay_5us(void) //延时函数
{
Delay_N10us(1);
Delay_N10us(1);
Delay_N10us(1);
Delay_N10us(1);
Delay_N10us(1);
}
void Delay_1ms(uint32_t t) //延时函数
{
while(t--)
{
SensorDelay_us(1000);//延时1ms
}
}
//void AHT20_Clock_Init(void) //延时函数
//{
// RCC_APB2PeriphClockCmd(CC_APB2Periph_GPIOB,ENABLE);
//}
void SDA_Pin_Output_High(void) //将PB7配置为输出 ， 并设置为高电平， PB7作为I2C的SDA
{
GPIO_InitTypeDef GPIO_InitStruct;
GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;//推挽输出
GPIO_InitStruct.Pin = GPIO_PIN_7;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;
HAL_GPIO_Init(GPIOB,& GPIO_InitStruct);
HAL_GPIO_WritePin(GPIOB,GPIO_PIN_7,GPIO_PIN_SET);
}
void SDA_Pin_Output_Low(void) //将P7配置为输出 并设置为低电平
{
GPIO_InitTypeDef GPIO_InitStruct;
GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;//推挽输出
GPIO_InitStruct.Pin = GPIO_PIN_7;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;
HAL_GPIO_Init(GPIOB,& GPIO_InitStruct);
HAL_GPIO_WritePin(GPIOB,GPIO_PIN_7,GPIO_PIN_RESET);
}
void SDA_Pin_IN_FLOATING(void) //SDA配置为浮空输入
{
GPIO_InitTypeDef GPIO_InitStruct;
GPIO_InitStruct.Mode = GPIO_MODE_INPUT;//浮空
GPIO_InitStruct.Pin = GPIO_PIN_7;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;
HAL_GPIO_Init( GPIOB,&GPIO_InitStruct);
}
void SCL_Pin_Output_High(void) //SCL输出高电平，P14作为I2C的SCL
{
HAL_GPIO_WritePin(GPIOB,GPIO_PIN_6,GPIO_PIN_SET);
}
void SCL_Pin_Output_Low(void) //SCL输出低电平
{
HAL_GPIO_WritePin(GPIOB,GPIO_PIN_6,GPIO_PIN_RESET);
}
void Init_I2C_Sensor_Port(void) //初始化I2C接口,输出为高电平
{
GPIO_InitTypeDef GPIO_InitStruct;
GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;//推挽输出
GPIO_InitStruct.Pin = GPIO_PIN_7;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;
HAL_GPIO_Init(GPIOB,& GPIO_InitStruct);
HAL_GPIO_WritePin(GPIOB,GPIO_PIN_15,GPIO_PIN_SET);
GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;//推挽输出
GPIO_InitStruct.Pin = GPIO_PIN_6;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;
HAL_GPIO_Init(GPIOB,& GPIO_InitStruct);
HAL_GPIO_WritePin(GPIOB,GPIO_PIN_15,GPIO_PIN_SET);
}
void I2C_Start(void) //I2C主机发送START信号
{
SDA_Pin_Output_High();
SensorDelay_us(8);
SCL_Pin_Output_High();
SensorDelay_us(8);
SDA_Pin_Output_Low();
SensorDelay_us(8);
SCL_Pin_Output_Low();
SensorDelay_us(8);
}
void AHT20_WR_Byte(uint8_t Byte) //往AHT20写一个字节
{
uint8_t Data,N,i;
Data=Byte;
i = 0x80;
for(N=0;N<8;N++)
{
SCL_Pin_Output_Low();
Delay_4us();
if(i&Data)
{
SDA_Pin_Output_High();
}
else
{
SDA_Pin_Output_Low();
}
SCL_Pin_Output_High();
Delay_4us();
Data <<= 1;
}
SCL_Pin_Output_Low();
SensorDelay_us(8);
SDA_Pin_IN_FLOATING();
SensorDelay_us(8);
}
uint8_t AHT20_RD_Byte(void)//从AHT20读取一个字节
{
uint8_t Byte,i,a;
Byte = 0;
SCL_Pin_Output_Low();
SDA_Pin_IN_FLOATING();
SensorDelay_us(8);
for(i=0;i<8;i++)
{
SCL_Pin_Output_High();
Delay_5us();
a=0;
//if(GPIO_ReadInputDataBit(GPIOB,GPIO_Pin_15)) a=1;
if(HAL_GPIO_ReadPin(GPIOB,GPIO_PIN_7)) a=1;
Byte = (Byte<<1)|a;
//SCL_Pin_Output_Low();
HAL_GPIO_WritePin(GPIOB,GPIO_PIN_6,GPIO_PIN_RESET);
Delay_5us();
}
SDA_Pin_IN_FLOATING();
SensorDelay_us(8);
return Byte;
}
uint8_t Receive_ACK(void) //看AHT20是否有回复ACK
{
uint16_t CNT;
CNT = 0;
SCL_Pin_Output_Low();
SDA_Pin_IN_FLOATING();
SensorDelay_us(8);
SCL_Pin_Output_High();
SensorDelay_us(8);
while((HAL_GPIO_ReadPin(GPIOB,GPIO_PIN_7)) && CNT < 100)
CNT++;
if(CNT == 100)
{
return 0;
}
SCL_Pin_Output_Low();
SensorDelay_us(8);
return 1;
}
void Send_ACK(void) //主机回复ACK信号
{
SCL_Pin_Output_Low();
SensorDelay_us(8);
SDA_Pin_Output_Low();
SensorDelay_us(8);
SCL_Pin_Output_High();
SensorDelay_us(8);
SCL_Pin_Output_Low();
SensorDelay_us(8);
SDA_Pin_IN_FLOATING();
SensorDelay_us(8);
}
void Send_NOT_ACK(void) //主机不回复ACK
{
SCL_Pin_Output_Low();
SensorDelay_us(8);
SDA_Pin_Output_High();
SensorDelay_us(8);
SCL_Pin_Output_High();
SensorDelay_us(8);
SCL_Pin_Output_Low();
SensorDelay_us(8);
SDA_Pin_Output_Low();
SensorDelay_us(8);
}
void Stop_I2C(void) //一条协议结束
{
SDA_Pin_Output_Low();
SensorDelay_us(8);
SCL_Pin_Output_High();
SensorDelay_us(8);
SDA_Pin_Output_High();
SensorDelay_us(8);
}
uint8_t AHT20_Read_Status(void)//读取AHT20的状态寄存器
{
uint8_t Byte_first;
I2C_Start();
AHT20_WR_Byte(0x71);
Receive_ACK();
Byte_first = AHT20_RD_Byte();
Send_NOT_ACK();
Stop_I2C();
return Byte_first;
}
uint8_t AHT20_Read_Cal_Enable(void) //查询cal enable位有没有使能
{
uint8_t val = 0;//ret = 0,
val = AHT20_Read_Status();
if((val & 0x68)==0x08)
return 1;
else return 0;
}
void AHT20_SendAC(void) //向AHT20发送AC命令
{
I2C_Start();
AHT20_WR_Byte(0x70);
Receive_ACK();
AHT20_WR_Byte(0xac);//0xAC采集命令
Receive_ACK();
AHT20_WR_Byte(0x33);
Receive_ACK();
AHT20_WR_Byte(0x00);
Receive_ACK();
Stop_I2C();
}
//CRC校验类型：CRC8/MAXIM
//多项式：X8+X5+X4+1
//Poly：0011 0001 0x31
//高位放到后面就变成 1000 1100 0x8c
//C现实代码：
uint8_t Calc_CRC8(uint8_t *message,uint8_t Num)
{
uint8_t i;
uint8_t byte;
uint8_t crc=0xFF;
for(byte=0; byte<Num; byte++)
{
crc^=(message[byte]);
for(i=8;i>0;--i)
{
if(crc&0x80) crc=(crc<<1)^0x31;
else crc=(crc<<1);
}
}
return crc;
}
void AHT20_Read_CTdata(uint32_t *ct) //没有CRC校验，直接读取AHT20的温度和湿度数据
{
volatile uint8_t Byte_1th=0;
volatile uint8_t Byte_2th=0;
volatile uint8_t Byte_3th=0;
volatile uint8_t Byte_4th=0;
volatile uint8_t Byte_5th=0;
volatile uint8_t Byte_6th=0;
uint32_t RetuData = 0;
uint16_t cnt = 0;
AHT20_SendAC();//向AHT10发送AC命令
Delay_1ms(80);//延时80ms左右
cnt = 0;
while(((AHT20_Read_Status()&0x80)==0x80))//直到状态bit[7]为0，表示为空闲状态，若为1，表示忙状态
{
SensorDelay_us(1508);
if(cnt++>=100)
{
break;
}
}
I2C_Start();
AHT20_WR_Byte(0x71);
Receive_ACK();
Byte_1th = AHT20_RD_Byte();//状态字，查询到状态为0x98,表示为忙状态，bit[7]为1；状态为0x1C，或者0x0C，或者0x08表示为空闲状态，bit[7]为0
Send_ACK();
Byte_2th = AHT20_RD_Byte();//湿度
Send_ACK();
Byte_3th = AHT20_RD_Byte();//湿度
Send_ACK();
Byte_4th = AHT20_RD_Byte();//湿度/温度
Send_ACK();
Byte_5th = AHT20_RD_Byte();//温度
Send_ACK();
Byte_6th = AHT20_RD_Byte();//温度
Send_NOT_ACK();
Stop_I2C();
RetuData = (RetuData|Byte_2th)<<8;
RetuData = (RetuData|Byte_3th)<<8;
RetuData = (RetuData|Byte_4th);
RetuData =RetuData >>4;
ct[0] = RetuData;//湿度
RetuData = 0;
RetuData = (RetuData|Byte_4th)<<8;
RetuData = (RetuData|Byte_5th)<<8;
RetuData = (RetuData|Byte_6th);
RetuData = RetuData&0xfffff;
ct[1] =RetuData; //温度
}
void AHT20_Read_CTdata_crc(uint32_t *ct) //CRC校验后，读取AHT20的温度和湿度数据
{
volatile uint8_t Byte_1th=0;
volatile uint8_t Byte_2th=0;
volatile uint8_t Byte_3th=0;
volatile uint8_t Byte_4th=0;
volatile uint8_t Byte_5th=0;
volatile uint8_t Byte_6th=0;
volatile uint8_t Byte_7th=0;
uint32_t RetuData = 0;
uint16_t cnt = 0;
// uint8_t CRCDATA=0;
uint8_t CTDATA[6]={
0};//用于CRC传递数组
AHT20_SendAC();//向AHT10发送AC命令
Delay_1ms(80);//延时80ms左右
cnt = 0;
while(((AHT20_Read_Status()&0x80)==0x80))//直到状态bit[7]为0，表示为空闲状态，若为1，表示忙状态
{
SensorDelay_us(1508);
if(cnt++>=100)
{
break;
}
}
I2C_Start();
AHT20_WR_Byte(0x71);
Receive_ACK();
CTDATA[0]=Byte_1th = AHT20_RD_Byte();//状态字，查询到状态为0x98,表示为忙状态，bit[7]为1；状态为0x1C，或者0x0C，或者0x08表示为空闲状态，bit[7]为0
Send_ACK();
CTDATA[1]=Byte_2th = AHT20_RD_Byte();//湿度
Send_ACK();
CTDATA[2]=Byte_3th = AHT20_RD_Byte();//湿度
Send_ACK();
CTDATA[3]=Byte_4th = AHT20_RD_Byte();//湿度/温度
Send_ACK();
CTDATA[4]=Byte_5th = AHT20_RD_Byte();//温度
Send_ACK();
CTDATA[5]=Byte_6th = AHT20_RD_Byte();//温度
Send_ACK();
Byte_7th = AHT20_RD_Byte();//CRC数据
Send_NOT_ACK(); //注意: 最后是发送NAK
Stop_I2C();
if(Calc_CRC8(CTDATA,6)==Byte_7th)
{
RetuData = (RetuData|Byte_2th)<<8;
RetuData = (RetuData|Byte_3th)<<8;
RetuData = (RetuData|Byte_4th);
RetuData =RetuData >>4;
ct[0] = RetuData;//湿度
RetuData = 0;
RetuData = (RetuData|Byte_4th)<<8;
RetuData = (RetuData|Byte_5th)<<8;
RetuData = (RetuData|Byte_6th);
RetuData = RetuData&0xfffff;
ct[1] =RetuData; //温度
}
else
{
ct[0]=0x00;
ct[1]=0x00;//校验错误返回值，客户可以根据自己需要更改
}//CRC数据
}
void AHT20_Init(void) //初始化AHT20
{
Init_I2C_Sensor_Port();
I2C_Start();
AHT20_WR_Byte(0x70);
Receive_ACK();
AHT20_WR_Byte(0xa8);//0xA8进入NOR工作模式
Receive_ACK();
AHT20_WR_Byte(0x00);
Receive_ACK();
AHT20_WR_Byte(0x00);
Receive_ACK();
Stop_I2C();
Delay_1ms(10);//延时10ms左右
I2C_Start();
AHT20_WR_Byte(0x70);
Receive_ACK();
AHT20_WR_Byte(0xbe);//0xBE初始化命令，AHT20的初始化命令是0xBE, AHT10的初始化命令是0xE1
Receive_ACK();
AHT20_WR_Byte(0x08);//相关寄存器bit[3]置1，为校准输出
Receive_ACK();
AHT20_WR_Byte(0x00);
Receive_ACK();
Stop_I2C();
Delay_1ms(10);//延时10ms左右
}
void JH_Reset_REG(uint8_t addr)
{
uint8_t Byte_first,Byte_second,Byte_third;
I2C_Start();
AHT20_WR_Byte(0x70);//原来是0x70
Receive_ACK();
AHT20_WR_Byte(addr);
Receive_ACK();
AHT20_WR_Byte(0x00);
Receive_ACK();
AHT20_WR_Byte(0x00);
Receive_ACK();
Stop_I2C();
Delay_1ms(5);//延时5ms左右
I2C_Start();
AHT20_WR_Byte(0x71);//
Receive_ACK();
Byte_first = AHT20_RD_Byte();
Send_ACK();
Byte_second = AHT20_RD_Byte();
Send_ACK();
Byte_third = AHT20_RD_Byte();
Send_NOT_ACK();
Stop_I2C();
Delay_1ms(10);//延时10ms左右
I2C_Start();
AHT20_WR_Byte(0x70);///
Receive_ACK();
AHT20_WR_Byte(0xB0|addr);寄存器命令
Receive_ACK();
AHT20_WR_Byte(Byte_second);
Receive_ACK();
AHT20_WR_Byte(Byte_third);
Receive_ACK();
Stop_I2C();
Byte_second=0x00;
Byte_third =0x00;
}
void AHT20_Start_Init(void)
{
JH_Reset_REG(0x1b);
JH_Reset_REG(0x1c);
JH_Reset_REG(0x1e);
}
- Delete the main function in the main.c file, including the header file above, and replace it with the following code
#include "main.h"
#include "dma.h"
#include "i2c.h"
#include "usart.h"
#include "gpio.h"
#include "AHT20-21_DEMO_V1_3.h"
#include <stdio.h>
#include <string.h>
int fputc(int ch,FILE *f)//重新printf
{
HAL_UART_Transmit(&huart1,(uint8_t *)&ch,1,0xFFFF);
while(__HAL_UART_GET_FLAG(&huart1,UART_FLAG_TC)!=SET){
}
return ch;
}
void SystemClock_Config(void);
volatile int c1,t1;
uint32_t CT_data[2]={
0,0};
int main(void)
{
HAL_Init();
SystemClock_Config();
MX_USART1_UART_Init();
MX_DMA_Init();
MX_I2C1_Init();
AHT20_Init();//放在其它之后
if((AHT20_Read_Status()&0x18)!=0x18)
{
AHT20_Start_Init(); //重新初始化寄存器
Delay_1ms(10);
}
while (1)
{
AHT20_Read_CTdata(CT_data); //不经过CRC校验，直接读取AHT20的温度和湿度数据 推荐每隔大于1S读一次
//AHT20_Read_CTdata_crc(CT_data); //crc校验后，读取AHT20的温度和湿度数据
c1 = CT_data[0]*100*10/1024/1024; //计算得到湿度值c1（放大了10倍）
t1 = CT_data[1]*200*10/1024/1024-500;//计算得到温度值t1（放大了10倍）
printf("湿度：%d%s",c1/10,"%");
printf("温度：%d%s",t1/10,"℃");
printf("\r\n");
HAL_Delay(3000);
}
}
There is no problem with compiling and burning
3. Effect
20221116_233110
Four. Summary
Learned the IIC agreement, clear the general flow of the agreement. Experimenting with the sensor for the first time, it was cool. It is also the first time to call the manufacturer's code, and it is quite convenient to configure it through STM32Cube. This should be the norm in future work (using the manufacturer's code).
5. References
https://blog.csdn.net/qq_43279579/article/details/111597278
https://blog.csdn.net/Mouer__/article/details/121514102