SIM7600 and ThingSpeak, unable to publish

[HappyUser]

Dear all,
I nearly got SIM7600, MQTT and Thingspeak working. But I am not able to get the public working.
This is my basic syntax:
The module returns OK status, so so far so good. But no data shows up in my channel.
The weird things is I use the same Topic and message structure as with my SIM7080 module, and that works. Any suggestions?

My last part of the code :

String payload="channels/"+ String(ChannelId)+"/publish";
int Payload_Length;
Payload_Length=payload.length();

SerialAT.println("AT+CMQTTTOPIC=0,"+String(Payload_Length)); // Input the publish message topic <client_index,req_length>
SerialAT.println(payload);
Read_Response_Ignore_OK(3000);

payload="field1=345&field2=543";
Serial.print(" ");
Payload_Length=payload.length();
Serial.println ("AT+CMQTTPAYLOAD=0,"+String(Payload_Length));
SerialAT.println("AT+CMQTTPAYLOAD=0,"+String(Payload_Length)); // input the publish message body <client_index,req_length>
SerialAT.println(payload);
//delay(50);
Read_Response_Ignore_OK(1000);

SerialAT.println("AT+CMQTTPUB=0,0,60,0,0"); // Publish a message to the server <client_id,qos,pub_timeout,retained>
Read_Response_Ignore_OK(1000);

[felmue]

Hello @HappyUser

according to the documentation, after sending the AT+CMQTTTOPIC=0,<length> command the modem answers with a prompt > after which the topic can be sent. However your code seems to sent the topic right after issuing the command. Maybe try adding a short delay?

Same for the payload - try with a short delay before sending the payload.

If that solves the issue then of course the proper solution would be to actually wait for the prompt (or error) with a timeout.

Thanks
Felix

[HappyUser]

@felmue And indeed, I needed to add a delay before sending the payload. I had hoped that it would be necessary (in order to speed up he process of waking up, sending and going to sleep).
Regards