I am currently working with the Quectel EC200UCNAP-N05-SGNSA module and facing an issue while establishing and maintaining an MQTT connection to our server.
Problem Description:
- The MQTT connection is established successfully.
- Upon publishing the registration packet, the module often disconnects from the server immediately afterward.
- In certain cases, the registration packet is successfully delivered to the server, yet the module still responds with
+QMTSTAT: 0,1. - I have already configured the keep-alive interval using:
AT+QMTCFG=“keepalive”,0,120
Current Command Sequence:
mqtt_commands_t Registration_buff[BUFFER_SIZE_30] = {
e_mqtt_check_sim_sts, // Check SIM status
e_mqtt_check_ntwrk_sts, // Check network registration
e_mqtt_keepalive, // Set keep-alive
e_mqtt_check_ntwrk_band, // Check network band
e_mqtt_check_signal_strngth,// Signal strength
e_mqtt_rqst_imei, // IMEI
e_mqtt_rqst_imsi, // IMSI
e_mqtt_open_st05, // MQTT open
e_mqtt_keepalive,
e_mqtt_connect_st05, // MQTT connect
e_mqtt_snd_reg_packet, // Publish registration packet
e_mqtt_close,
e_mqtt_open_st05,
e_mqtt_connect_st05,
e_mqtt_subscribe, // Subscribe to topic
e_mqtt_close
};
The response is:
AT+CPIN?
+CPIN: READY
OK
AT+CREG?
+CREG: 0,1
OK
AT+QMTCFG=“keepalive”,0,120
OK
AT+QENG=“servingcell”
+QENG: “servingcell”,“NOCONN”,“LTE”,“TDD”,404,45,AD69901,400,39125,40,4,4,2162,-130,-16,-96,36,-
OK
AT+CSQ
+CSQ: 8,99
OK
AT+CGSN
867950072779232
OK
AT+CIMI
404450660781137
OK
AT+QMTOPEN=0,“server_link”,1884
OK
AT+QMTCFG=“keepalive”,0,120
OK
AT+QMTCONN=0,“clientID”,“usrname”,“password”,
OK
+QMTCONN: 0,0,0
AT+QMTPUBEX=0,0,0,0,“Name/867950072779232/METADATA_SYNC”,69
{“date_time”:1747295948000,“ic_imei”:“867950072779232”,“version”:0}
OK
+QMTPUBEX: 0,0,0
AT+QMTCLOSE=0
ERROR
AT+QMTOPEN=0,“server”,1884
OK
+QMTOPEN: 0,0
AT+QMTCONN=0,“client id”,“usrname”,“password”,
OK
+QMTCONN: 0,0,0
AT+QMTSUB=0,1,“name/867950072779232/METADATA_SYNC_ACK”,0
ERROR
+QMTSTAT: 0,1
Could you please help investigate:
- Why the module is getting disconnected after
QMTPUBEX, even with a successful publish? - If any timing or sequence issue exists in the current flow.
- Whether additional configurations (e.g., QoS, retry handling, connection persistence) are required.
- If there are module-specific recommendations for weak signal conditions during MQTT operations.
- The server is expected to send three acknowledgements upon receiving the metadata.
- However, the connection is dropped before acknowledgements are received.
- Signal strength is around CSQ: 8,99 (marginal but connected).
Thank you.
