stm8s development (eight) use of IIC: IIC host communication!

We have talked about two commonly used serial ports, UART and SPI. This time, we will talk about another commonly used serial port: IIC (I2C) communication.

Popular Science IIC: Generally there are two signal lines, one is the bidirectional data line SDA, the other is the clock line SCL. All serial data SDA connected to the IIC bus device is connected to the bus SDA, and the clock line SCL of each device is connected to the bus SCL.

Communication process:
In master mode, the IIC interface starts data transmission and generates a clock signal. Serial data transmission always starts with a start condition and ends with a stop condition. Both the start condition and the stop condition are generated by software control in master mode.
In slave mode, the IIC interface can recognize its own address (7 or 10 bits) and the general call address. The software can control the opening or closing of the recognition of the general call address.
Data and address are transmitted in 8 bits/byte, with the high bit first. The 1 or 2 bytes following the start condition are the address (1 byte in 7-bit mode and 2 bytes in 10-bit mode). The address is only sent in master mode.
During the 9th clock after 8 clocks of a byte transmission, the receiver must send back an acknowledge bit (ACK) to the transmitter. Refer to the figure below.

For detailed protocol, please refer to: http://blog.csdn.net/subkiller/article/details/6854910

Similar to SPI, using IIC is nothing more than initialization, data sending, and data receiving, three major functions.

Initialization is divided into master and slave, but generally the microcontroller that communicates with external chips acts as the master.

1. void IIC_Master_Init(void)  

2. {  

3.   CLK_PCKENR1 |= 0x01; //Enable IIC peripheral clock  

4.     

5.   PB_DDR &= 0xcf;  

6.   PB_CR1 &= 0xcf;  

7.   PB_CR2 &= 0xcf;  

8.     

9.   I2C_CR1 = 0x00; //Allow clock stretching, disable broadcast call, disable iic  

10.   I2C_FREQR = 0x01; //Input clock frequency 8MHz  

11.   I2C_OARH = 0x40; // seven-bit address mode  

12.   I2C_OARL = 0xa0; //Own address 0xa0  

13.   I2C_CCRL = 0xff; //  

14.   I2C_CCRH = 0x00; //Standard mode  

15.   I2C_TRISER = 0x02;  

16.   I2C_CR1 |= 0x01; // Enable iic peripheral  

17. }  

Here we use the IIC pins PB4 and PB5 on the STM8S105 chip. In addition, we need to enable the IIC clock.

Here we only give a simple example of sending and receiving data, because different external chips have different communication methods, but generally they are:

Read operation: Start -> Send peripheral address -> Start -> Send register address to be read -> Read one byte -> (may read another byte) -> ... -> End
Write operation: Start -> Send peripheral address -> Send register address to be written -> Write one byte -> 

1. void IIC_Write_Byte(u8 DeviceAddress, u8 Address, u8 Data)  

2. {  

3.   vu8 temp = 0;  

4.   while((I2C_SR3 & 0x02) != 0); //Wait for the IIC bus to be idle  

5.   IIC_Start();  

6.   while((I2C_SR1 & 0x01) == 0); //EV5, the start signal has been sent  

7.   I2C_DR = (DeviceAddress & 0xfe); // Send the physical address of the iic slave device, the lowest bit is 0, write operation  

8.   while((I2C_SR1 & 0x02) == 0); //The address has been sent  

9.   temp = I2C_SR1; //Clear ADDR flag  

10.   temp = I2C_SR3;  

11.   while((I2C_SR1 & 0x80) == 0); //Wait for the send register to be empty  

12.   I2C_DR = Address; //Send the register address to be written  

13.   while((I2C_SR1 & 0x04) == 0); //Wait for sending to complete  

14.   while((I2C_SR1 & 0x80) == 0); //Wait for the send register to be empty  

15.   I2C_DR = Data; //Send the data to be written  

16.   while((I2C_SR1 & 0x04) == 0); //Wait for sending to complete  

17.   temp = I2C_SR1; //Clear BTF flag  

18.   temp = I2C_DR;  

19.   IIC_Stop(); //Send stop signal  

20. }  

21.   

22. unsigned char IIC_Read_Byte(u8 DeviceAddress, u8 Address)  

23. {  

24.   vu8 temp = 0;  

25.   short read_data = 0;  

26.   while((I2C_SR3 & 0x02) != 0); //Wait for the IIC bus to be idle  

27.   I2C_CR2 |= 0x04; //Enable ACK  

28.   IIC_Start();  

29.   while((I2C_SR1 & 0x01) == 0); //EV5, the start signal has been sent  

30.   I2C_DR = (DeviceAddress & 0xfe); // Send the physical address of the iic slave device, the lowest bit is 0, write operation  

31.   while((I2C_SR1 & 0x02) == 0); //The address has been sent  

32.   temp = I2C_SR1; //Clear ADDR flag  

33.   temp = I2C_SR3;  

34.   while((I2C_SR1 & 0x80) == 0); //Wait for the send register to be empty  

35.   I2C_DR = Address; // Send the register address to be read  

36.   while((I2C_SR1 & 0x04) == 0); //Wait for data to be sent  

37.     

38.   IIC_Start();  

39.   while((I2C_SR1 & 0x01) == 0); //EV5, the start signal has been sent  

40.   I2C_DR = (DeviceAddress | 0x01); // Send the physical address of the IIC slave device, the lowest bit is 1, read operation  

41.   while((I2C_SR1 & 0x02) == 0); //The address has been sent  

42.   temp = I2C_SR1; //Clear ADDR flag  

43.   temp = I2C_SR3;  

44.   while((I2C_SR1 & 0x40) == 0); //Wait for the receive data register to be non-empty  

45.   read_data = I2C_DR;  

46.   I2C_CR2 &= 0xfb; //When reading data, sending stop must disable ack to release the slave  

47.   temp = I2C_SR1; //Clear BTF flag  

48.   temp = I2C_DR;  

49.   IIC_Stop();  

50.   return read_data;  

51. }  

Attached is the project of stm8s in IAR environment, including the initialization code of on-chip hardware such as SPI, IIC, PWM, AWU, USART, EEPROM, etc.

http://download.csdn .NET /detail/devintt/9454188

Read operation: Start -> Send peripheral address -> Start -> Send register address to be read -> Read one byte -> (may read another byte) -> ... -> End