Hardware and interface learning summary

One 、 Synchronous and asynchronous communication

asynchronous ： There is no clock line between the two devices , But both sides of the equipment need to maintain the same communication baud rate , Here's the picture , There is no data cable SCL Clock line .

Sync ： Sometimes the clock line , Same communication speed , Therefore, it is no longer necessary to configure the same speed . Here's the picture , In addition to the data line for exchanging information , also SCL Clock line .

Two 、IIC How to mount multiple devices at the same time

I2C Bus is a master-slave structure bus ,I2C Each device on the bus can act as a master or slave device , The master device is used to generate clock signals that allow transmission , And initialize the data transmission of the bus , So the main equipment is usually CPU.

Because a I2C There can be multiple slaves on the bus , In this way, the master device needs to determine the address to communicate with cabinet devices .I2C Bus sang each slave device has a unique 7bit Address physical identification . because I2C Full address 0 For broadcast address , therefore I2C Theoretically, the bus can carry at most 2^7-1=127 Slave devices .

Host sending data flow

1、 When the host detects that the bus is idle , Send a start signal “S”, Start communicating ;
2、 The host then sends a slave address , from 7bit Physical address and 1bit Read and write control bits of W/R form ;
3、 Identify by address , The corresponding slave sends back a reply signal to the host after receiving the command （ACK=0）;
4、 After receiving the response signal from the slave, the host starts to send the first byte of data ;
5、 After receiving the data, the slave returns a reply signal ACK;
6、 The host will send the next data byte after receiving the response signal ;
7、 The host sends the last byte and receives ACK after , Send a stop signal to the slave P End this communication and release the bus ;
8、 It's on the slave P After the signal, it also exits the communication with the host .

The process of sending data from the machine

1、 The host sends a start signal , Then send the address bytes ;
2、 After the corresponding slave receives the address bytes , Return a reply signal and send data to the host ;
3、 After receiving the data, the master feeds back a reply signal to the slave ACK;
4、 After receiving the response signal, the slave continues to send the next data to the host ;
5、 When the host finishes receiving data , Send a to the slave NAK, The slave will stop sending after receiving the non reply signal ;
6、 After the host sends a non reply signal , Send another stop signal , Release the bus and end the communication .

3、 ... and 、 What is the interruption process ？

CPU
1、 Judge interruption , Find interrupt number
2、 Determine priority
3、 Save the scene （ Pressing stack ）
4、 Find the interrupted service handler
5、 Handle interrupt handlers
6、 Back to the scene , Continue with the original procedure