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1. Program architecture

A good program architecture must meet at least the following requirements:

The program code of the hardware layer and the application layer are separated, the control and communication between each other use interfaces, and will not share global variables or arrays.

To describe it in technical terms is portability and extensibility.

When 51 single-chip microcomputer writes the program, basically a .c file is solved, including register configuration and product functions. When it comes to stm32, we will write different peripheral functions, such as led, keys, serial port and other peripheral function codes in different .c files, and then uniformly use the function interface to call it, for example, to control a LED light on, directly in the led.c file to write a function to drive the state of led lights and then give external calls. The code of the hardware layer and the application layer are separated, and the application layer is controlled by the interface provided by the hardware layer, and there will not be all variables or arrays shared by the hardware layer and the application layer.

In another case, the application needs to collect data from the hardware layer, such as serial port to receive data, keystroke collection, ADC value collection, how should this value be obtained from the hardware layer?

The simple way is to use a global variable or array, for example, if the hardware layer serial port receives the data, then we throw the data into the array, and then set the flag of the received global variable to 1, for example, the global variable is named RcvFlag, and then the application layer program will poll to determine the RcvFlag==1? If so, take the data out of the array and parse it.

However, this method has the problems of poor real-time performance and poor portability. for example, the hardware layer of the serial port needs to be encapsulated for the customer to use, and the customer can not see the source code of the implementation, so it can only provide the function interface for the customer to use. it is impossible to tell the customer which variable is 1 first and then take the data in which array.

You need a callback function here.

two。 The function of callback function

In stm32, such as external interrupt, timer interrupt, serial port interrupt are similar to callback function, the purpose of this function is to pass the collected data to cpu for use.

The core role of the callback function:

Transfer data from one .c file to another.

3. Master the programming of callback function

The disadvantages of traditional writing methods are:

1. Poor portability

2. Poor real-time performance

3. It is difficult to encapsulate functional codes.

The callback function is written:

Main.c Code:

# include # include "key.h" void KeyScanHandle (KEY_ID_TYPEDEF KeyID,KEY_STATE_TYPEDEF KeyState) {/ / if (KeyID= = KEY2) / / {/ / if (KeyState= KEY_PRESS) / / {printf ("KeyID=%d, KeyState=%d\ r\ n", KeyID,KeyState); / /} /} int main (int argc, char * argv []) {KeyInit () KeyScanCBSRegister (KeyScanHandle); KeyPoll (); return 0;}

Key.c Code:

# include "key.h" KEY_ID_TYPEDEF keyVal; / / Button IDKEY_STATE_TYPEDEF keyState; pKeyScanCallBack pKeyScanCBS;void KeyInit () {keyVal = 0; keyState = KEY_IDLE; pKeyScanCBS = 0;} void KeyScanCBSRegister (pKeyScanCallBack pCBS) {if (pKeyScanCBS = = 0) {pKeyScanCBS = pCBS;}} void KeyPoll () {printf ("Please Enter key value:") If (scanf ("% d", & keyVal) = = 1) {printf ("\ r\ n"); printf ("Please enter key state:"); if (scanf ("% d", & keyState) = = 1) {if (pKeyScanCBS! = 0) {pKeyScanCBS (keyVal,keyState);}}

Key.h Code:

# ifndef _ KEY_H_#define _ KEY_H_typedef enum {KEY1, KEY2,} KEY_ID_TYPEDEF;typedef enum {KEY_IDLE, / / idle KEY_PRESS, / / short press KEY_LONG_PRESS, / / long press KEY_RELEASE,// key release} KEY_STATE_TYPEDEF; typedef void (* pKeyScanCallBack) (KEY_ID_TYPEDEF KeyID,KEY_STATE_TYPEDEF KeyState); void KeyInit (); void KeyPoll () Void KeyScanCBSRegister (pKeyScanCallBack pCBS); # endif4. Application of callback function in products

Make different functions according to the contents of different frames received

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