Question

Hi,

I use a TRB255 but when I try to connect I always get "NO CARRIER". I have SIM cards inserted.

BR

Jonas

Answer 1

Hello,

    

Does the TRB255 also refuse to connect when the modem is controlled by the device itself?

If so, I will ask you to navigate to System → Administration → Troubleshoot and generate a troubleshoot file. It will contain the logs from the device and will help me determine what could be causing the issue.

Could you also post the output of the commands AT+COPS? and AT+CREG?

    

Best regards,
DaumantasG

Comments

+COPS: 0

+CREG: 0,0

I've attached a troubleshoot file to this ticket.

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Hello,

  

Thank you. Could you attach a troubleshoot file when the device is in control of the modem (serial modem control disabled)?

If the connection establishes when the TRB255 is in control, then perhaps you are missing some AT command when you are in control of the modem? Could you clarify what you are using the modem for?

AT Command manual for this modem can be found here (registration needed).

  

Best regards,
DaumantasG

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I've attached the file AT_commands_1.txt. There you have all AT commands sent and received by the modem.

A few seconds after that we try to connect with ATD*99# the modem sends NO CARRIER.

In data mode some data is sent as you can see.

We use the modem to connect to a AWS server.
The device which sends commands to the modem works with the TRB142 modem using the same AT commands. It can connect over PPP and receive IP address and name servers.

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I've attached a troubleshoot file when serial modem control is disabled:
diasbled_troubleshoot-Teltonika-TRB255.com-2023-05-17.tar.gz

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Hello,

 

Could you try using a semicolon (;) after the ATD command to check if the output is the same?

Very similar behavior on LTE networks can be observed when a semicolon is missing after the dial command, however, I'm not sure if this is also the case here.

Let me know how it goes.

 

Best regards,
DaumantasG