I2C bus learning (I)--signal type

     I2C (Inter-Integrated Circuit) bus is a two-wire serial bus developed by PHILIPS, which is used to connect microcontrollers and their peripheral devices. It is a serial bus composed of data line SDA and clock SCL, which can send and receive data.     

    Each device connected to the I2C bus has a unique address. Data transmission between the host and other devices can be done by the host sending data to other devices. In this case, the host is the transmitter, and the device receiving data on the bus is the receiver.
   Bidirectional transmission is carried out between the CPU and the controlled IC, and between ICs. The high-speed IIC bus can generally reach more than 400kbps. There are three types of signals in the I2C bus during data transmission, namely: start signal, end signal and response signal. 
　　Start signal: When SCL is high, SDA jumps from high level to low level to start data transmission. 
　　End signal: When SCL is high, SDA jumps from low level to high level to end data transmission. 
　　Response signal: After receiving 8-bit data, the IC receiving data sends a specific low-level pulse to the IC sending data, indicating that the data has been received. After the CPU sends a signal to the controlled unit, it waits for the controlled unit to send a response signal. After receiving the response signal, the CPU makes a judgment on whether to continue to transmit the signal based on the actual situation. If the response signal is not received, it is judged that the controlled unit has a fault. Among these signals, the start signal is required, while the end signal and the response signal are optional.

 Code:

(1) Start signal   

Void I2CStart(void)

{

  SomeNop() ;

  SCL = 1;

  SomeNop() ;

  SDA = 0;

  SomeNop() ;

  SCL = 0;

  SomeNop() ;

}

(2) Termination signal

void I2cStop(void)

{

    SDA = 0;

    SomeNop() ;

    SCL = 1;

    SomeNop() ;

    SDA = 1;

    SomeNop() ;

    SCL = 0;

}