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I have a Huawei USB stick (E3372h-320) running under Linux. I configured usb_modeswitch so it's switched into the modem mode (or "stick mode") rather than the "hilink" mode. I correctly get three /dev/ttyUSB* devices, and I'm playing around with AT commands.

The modem correctly registers in the network, AT+COPS? shows it's registered. I am definitely able to send and receive SMS messages without problems (using the AT+CMGF=1 + AT+CMGS=<number> commands. AT+CSQ gives good signal strength.

The SIM card works perfectly in a mobile phone.

So far so good. However, now I'm trying to get the modem to dial some number, and that's where things are not working. Any syntax for the ATD<number> command I tried (with/without quotes around the number, with/without semicolon at the end, with/without country code, with T, with P) resulted in an immediate NO CARRIER response from the modem.

Now I could certainly be missing something, but the main thing I'd like to understand now is: Is ATD supposed to be working in my scenario? Does it depend on the modem? On the operator? On the SIM? On something else? How do I check? Of course if it cannot work or is not supposed to be working, it's pointless for me to waste more time trying.

John Smith
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  • If I were you, I would move this to StackOverflow and post your code too. It is hard to judge without seeing what you are actually doing in the code. This site has a lot of mega-geeks (good ones too) but many/most don't read code or know how to interpret the ***hayes command set***. – Señor CMasMas Mar 30 '21 at 16:12
  • I'll take the advice, however there's really no code involved here, I'm typing everything into minicom. – John Smith Mar 30 '21 at 16:15
  • @JohnSmith you're in the right place. Does any of this help: https://superuser.com/questions/1079052/no-carrier-with-huawei-me906s – LawrenceC Mar 30 '21 at 16:21
  • Looks to me that the OP in that thread is trying to dial `*99#` (which AFAIK is not a regular number) to establish an IP link. Here I'm trying to dial a real phone number. Anyway, I tested the suggestions there: `AT^RFSWITCH?` results in `ERROR` for me. – John Smith Mar 30 '21 at 16:39
  • I'm not sure about whether I need a PDP context (and hence the `AT^NDISDUP` and/or `AT+CGDCONT` commands) to dial regular numbers, would be grateful for any clarification. – John Smith Mar 30 '21 at 17:33

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