EC20_MQTT RS-485 Data interaction using MQTT protoctol through EC20 4G module based on STM32 microcontroller modify these #define PRODUCTKEY "a1RWs8Cm26C" #define DEVICENAME "LX4GCSIC" #define DEVICESECRET "EOQp6uOKiHUMwl52FFBELoG2pKqJSTja"