HL7812 ATH returns NO CARRIER

Whenever I send the ATH command to the HL7812 it is replying with NO CARRIER.



This is a difference in behaviour to that seen with other modules we have used (HL4548, HL7692).

This is causing the Linux to abort the PPP connection attempt.

I have tested removing the ATH line from the chatscript and it does connect.
The ATH must be in there for some reason.


Hi @mark.bewley,

  1. Where did you get that chatscript file from?
  2. Have you followed the PPP Using Linux - Application Note correctly? Please kindly recheck.

Link for PPP Using Linux - Application Note: AirPrime - PPP Using Linux - Application Note


I forget, it was a few years ago we first setup the HL4548, I probably used/adapted a reference one already in our Debian image. Whatever we did it worked with the HL4548, so went with it.

I do remember the document - now you mention it - as it looks familiar, I did refer to during the HL4548 testing. It isn’t necessarily explicit.

The document doesn’t specifically include the ATH command. Therefore I can probably just remove it from the chatscript, with no implications on the modems we are using.


To complete this thread, I have simply removed the ATH command from our chatscript.