Maximum AT Command Wait

[Thomas]

Hi,

I am implementing timeouts on AT command socket send and receive functions. Currently I have a timeout of 5 minutes but that seems too low as the modem appears to take longer to respond when on the edge of coverage.

What is the maximum time taken for the modem to respond to a command?

Kind regards,

Thomas

[Albrecht Markus Schellenberger]

Hello Thomas,

which AT commands are you using that take time? Most AT commands should give a response quite quickly, while commands like searching for networks might take some time.

Regards,

Markus

[Thomas]

Hi Markus,

The problematic AT commands appear the AT%XVBAT and AT%XTEMP. We are sending these commands approximately every 60ms. When in coverage this is fine, but when on on the edge of coverage (unit is in a garage), the AT socket seems to stop responding.

What is strange is that this seems to occur exactly 1 minute and 40 seconds after the sending the AT+CFUN=1 command?

[Albrecht Markus Schellenberger]

Thanks for the feedback, Thomas!

That sounds strange, indeed! I wouldn’t have expected such response times for those AT commands.

Could you please provide me with a modem trace that captures the situation? Thanks!

Regards,

Markus

[Thomas]

Hi Markus,

I can't do that, it is happening to devices in the field that are battling to register, but only happening rarely.

[Thomas]

I think the issue is with the modem library. I've been trying to create error conditions and if you close an AT socket, or shutdown the modem library while a thread is either trying to receive or send on the socket, that thread is stuck forever. 

This could be fixed by using non blocking sockets and polling for events instead, but when you try and set the send function as non blocking on an AT socket, it returns an error. Any ideas? (Currently using v1.5.1 of the SDK)