STM32 HAL library for SIM800 (GPRS) release MQTT client over AT command

Simple C library (STM32 HAL) for working with the MQTT protocol through AT commands of the SIM800 (GPRS) module https://aliexpress.ru/item/32284560394.html?spm=a2g0s.9042311.0.0.34a833edF2cSsx

Configure STM32CubeMX by setting "General peripheral Initalizion as a pair of '.c / .h' file per peripheral" in the project settings. Remember to enable global interrupts for your UART. Copy the library header and source file to the appropriate project directories (Inc, Src). Configure the UART port where your module is connected in the MQTTSim800.h file.

#define UART_SIM800 &huart2
#define FREERTOS 0
#define CMD_DELAY 2000

In the head file of your project (main.c), include the header file

/ * USER CODE BEGIN Includes * /
#include "MQTTSim800.h"
/ * USER CODE END Includes * /

In the head file of your project (main.c), create SIM800 structure

/* USER CODE BEGIN PV */
SIM800_t SIM800;
/* USER CODE END PV */

add function call Sim800_RxCallBack () to interrupt UART

/ * USER CODE BEGIN 0 * /
void HAL_UART_RxCpltCallback(UART_HandleTypeDef * huart) {
    if (huart == UART_SIM800) {
        Sim800_RxCallBack();
    }
}
/ * USER CODE END 0 * /

Fill structure in the main (void) function section

/* USER CODE BEGIN 2 */
    SIM800.sim.apn = "internet";
    SIM800.sim.apn_user = "";
    SIM800.sim.apn_pass = "";
    SIM800.mqttServer.host = "mqtt.mqtt.ru";
    SIM800.mqttServer.port = 1883;
    SIM800.mqttClient.username = "user";
    SIM800.mqttClient.pass = "pass";
    SIM800.mqttClient.clientID = "TestSub";
    SIM800.mqttClient.keepAliveInterval = 120;
/* USER CODE END 2 */

add the module initialization code in the main (void) function section

/ * USER CODE BEGIN 2 * /
    MQTT_Init();
/ * USER CODE END 2 * /

add Subscription status

/ * USER CODE BEGIN 2 * /
    uint8_t sub = 0;
/ * USER CODE END 2 * /

add a send topic "STM32" and value "test" to the server in an infinite while (1) loop, for example every 1 seconds. add subscribe to topic "test"

 /* Infinite loop */
 /* USER CODE BEGIN WHILE */
 while (1) {
     if (SIM800.mqttServer.connect == 0) {
         MQTT_Init();
         sub = 0;
     }
     if (SIM800.mqttServer.connect == 1) {
         if(sub == 0){
             MQTT_Sub("test");
             sub = 1;
         }
         MQTT_Pub("STM32", "test");

         if(SIM800.mqttReceive.newEvent) {
             unsigned char *topic = SIM800.mqttReceive.topic;
             int payload = atoi(SIM800.mqttReceive.payload);
             SIM800.mqttReceive.newEvent = 0;
         }
     }
     HAL_Delay(1000);
     /* USER CODE END WHILE */

This completes the setup. Check in loop SIM800.mqttReceive.newEvent for new publish events. Set to 0 (zero) while use new data.

The library also supports sending zero messages to the server to maintain a connection.

MQTT_PingReq();

The library is implemented based on the code for generating MQTT packages of the project https://github.com/eclipse/paho.mqtt.embedded-c/tree/master/MQTTPacket

The library testing with https://github.com/r2axz/bluepill-serial-monster