cellular_modem sample for Quectel EG800Q

[MulattoKid]

Hi,

I'm working on getting the cellular_modem sample working on an MIMXRT1040-EVK with a Quectel EG800Q modem. The EG800Q and BG95 should be quite similar, so I tried building the modem_cellular driver for that modem. I ran into a problem where the dial-up (ATD*99***1#) would only work if I had a breakpoint between each AT command being sent. When just running normally I get a NO CARRIER response.

After some testing, I've found it to be due to AT+CFUN=4 in init_chat_script and AT+CFUN=1 in the dial_chat_script. If I remove AT+CFUN=4 the dial-up is able to connect.

My question is why the AT+CFUN=4 command is needed in the first place?
cc @bjarki-trackunit

[Mauricio-Alencar]

Hi @MulattoKid ,

You dont need to exeute AT+CFUN=4 first. AT+CFUN=4 put the modem in airplane mode and disable LTE antena circuits.

If you dont need to put in airplane mode, remove the AT+CFUN=4 in your logic and enter direclty in AT+CFUN=1.

[bjarki-andreasen]

The reason AT+CFUN=4 is sent is to "reset" the modem, closing any ongoing dial out andclosing pdp contexts. This is not always neccessary and sometimes even breaking, this is why there are custom chat scripts for each modem, so they can be tailored correctly :)

[MulattoKid]

Thanks for the clarification :)