Lua language (stm32+2g/4g module) and C language (stm32+esp8266) methods of extracting relevant data from strings - collation

One 、Lua Language to extract the desired data from the string

Lua Link to the use of regular expressions in

1、 problem

lua Language string extraction is in 2G Module and 4G Modular lua Used in code writing , It mainly deals with the data received by the serial port , Then extract each value , Assign to the corresponding variable , Form a new key value pair , Package and upload the data to Alibaba cloud

2、 Preliminary code

STM32+AIR800 Simple control of temperature and humidity collection and uploading to Alibaba cloud and issuing instructions from the cloud - link
String extraction used （ Yes STM32 The sent data is used to extract the temperature, humidity and smoke concentration ）： Although data is often not extracted , But the function can be realized , The code is like this ghost ：

3、 Code improvement

Occasionally used some time ago Cosmopolitan 4G modular when , Time interval 2 In, we need to extract the data received by the serial port , Use serial port to receive STM32 Data sent , For example, there is temperature , humidity , Carbon dioxide concentration 、 Status of each switch , This is definitely not enough , So take time to improve it

LUA Multiple data can be returned in the language , But there is also a hole in the use of regular expressions , Even the number of returned data is limited , Beyond the limit, there will be inexplicable errors ; When only fourorfive data were extracted in the early stage, everything was normal , When I need to send the status of each switch to 4g modular , When all written in one piece , It is impossible to extract data normally , There will also be problems with the data upload that could have been achieved , It took a while for this problem to be found and solved , Final solution ： That is to extract data twice to achieve your desired goal （ The following code ）

// Raw data ：
//temp:20,hum:30,co2:20,water_weight:100,food_weight:200.......
// To extract the value corresponding to the corresponding key 

    data = uart.read(UART_ID,"*l")-- Data received by serial port 
    a,b,c,d,e=string.match(data,'temp:(%d+),hum:(%d+),co2:(%d+),water_weight:(%d+),food_weight:(%d+)')
    f,g,h,i,j=string.match(data,'Led_switch_STA:(%d),Air_switch_STA:(%d),Water_switch_STA:(%d),Food_switch_STA:(%d),Temp_switch_STA:(%d)')
    if a~=nil and b~=nil and c~=nil and d~=nil and e~=nil then
		-- Execute corresponding statement 
    end
    if f~=nil and g~=nil and i~=nil and j~=nil and h~=nil then
			-- Execute corresponding statement 
    end

Two 、C Language - Extract the data you want from the string

1、 Have a problem

3-STM32+ESP8266 Connect onenet Upload data + Remote control （MQTT）- link
The reason why this string extraction is used , Because I'm using ESP8266 subscribe onenet When analyzing the data distributed by the cloud platform , If you use json analysis , Compiled code will exceed memory , Can't download to STM32 in （ chip STM32F103C6T6）, If you use STM32F103ZET6 or C8T6 When the master chip , Use json Data analysis is completely OK . To solve this problem , Therefore, string matching and string extraction methods are used to extract numerical values

sscanf stay c Usage in language - link

2、 Problem solving inspiration

The following code extracts the numbers and prints them ：

#include <stdio.h>
#include<string.h>
int main()
{
	int a,b,c;
	sscanf("2015.04.05", "%d.%d.%d", &a,&b,&c); // Get the required string    
    printf("a=%d,b=%d,c=%d\n",a,b,c);  //  a=2015,b=4,c=5
}

3、 resolvent

Extract some numbers from a string （ It is mainly used to extract the value corresponding to the key in the key value pair ）
For example, subscribe to the message , It exists in the form of key value pairs , We need to judge the value corresponding to the specified key
such as ：
（1） data “LED1”:1 in key “LED” Of value yes 1（ Judge LED1 Perform the open or close operation according to this instruction ）
（2） data “PWM”:245 In the key “PWM” The value is 245（ It is used to adjust the duty cycle and then adjust the light brightness ）

The following program is used to return PWM The corresponding value ,req And print the corresponding value ： Use two methods to extract （ Maybe there is a more suitable method , If you know something, you can add it in the comment area ）

#include <stdio.h>
#include<string.h>
int main()
{
	//char *st="{"PWM":200},req:129";//  Error definition ： stay C If you want to advance quotation marks in a language, you need to use escape characters 
	char *st="{\"PWM\":200},req:129";// Correct definition ： Define a string 
	char a,b,c,d,e,f;// Store characters  
	int num1,num2,num3,num4;
	// Method 1 ： 
	sscanf(st, "{\"%c%c%c\":%d},%c%c%c:%d",&a,&b,&c,&num1,&d,&e,&f,&num2); // Get the required string  
	printf("num1=%d,num2=%d\n",num1,num2);
	// Method 2  
	sscanf(st, "{\"PWM\":%d},req:%d", &num3,&num4); // Take the corresponding number directly  
	printf("num3=%d,num4=%d\n",num3,num4);
}

STM32 Using prototypes in ：

Subscribed data ：{“PWM”：123},req:11
Just extract PWM The value of

if(strstr((char *)req_payload, "PWM"))
{
		sscanf((char *)req_payload, "{\"%c%c%c\":%d", &a,&b,&c,&PWM_value); // Get the required string  
		printf("pwm_get_value=%d\r\n",PWM_value);
}