PPPoS of ESP-IDF falls back to 2G - cannot connect 4G

[duskotodevski]

Hi,
My setup is:
ESP-IDF v4.4.1,
Eclipse environment,
Board: LilyGo with modem SIM7000G

My goal is to implement PPPoS library (using the built-in example "pppos_client" from ESP-IDF) connect to internet on 4G (LTE) network, and run AWS-IOT application.

Initially this example offers working with two module types: BG96 and SIM800. Hence I have SIM7000G things shouldn't be so different.
So far I have achieved success (with little to no change) to the existing pppos library, by selecting SIM800. I had do send multiple AT in the beginning cause default baudrate of SIM7000 is "auto" so first couple of AT commands will not trigger any response, and that is fixed - problem solved.

I have pppos connectivity and I can successfully connect to the internet, and also my AWS-IOT library works fine through pppos.

The problem:

The problem is modem always connects with GPRS on 2G. If I previously set the modem to connect only on LTE (4G), when the pppos code kicks-in, somehow it magically drops the connection back to GPRS (2G). At least the LED state indicates that modem is actually on the 2G network.

My question is:
Does pppos library has anything to do with (re)instructing the modem to go on (2G) network in the several first instructions that it sends to the modem through ppp protocol, and if yes what do I have to change to achieve 4G (LTE) connection?

My hope is that pppos has nothing to do with the type of connection of the modem, and that my problem is eather with the modem pre-setup, or with my SIM card credentials. (my SIM work on my phone with 4G, but I dont exclude the possibility that the operator will not connect my SIM7000G to 4G intentionally - cause it can "see" that it is NOT A PHONE but M2M machine which falls back into another category of subscription - but that is yet to be researched...)

Experts in pppos, please drop your opinion, and any thoughts anyone?

Thanks in advance!

[felmue]

Hello @duskotodevski

using the pppos_client example my SIM7600G (sorry, I do not have a SIM7000G to test with) does properly connect to 4G with automatic provider selection (e.g. AT+COPS=0)

I've added the following line after the line which outputs the operator. It will tell which access technology has been selected.

Code: Select all

ESP_LOGI(TAG, "ACT: %d", dce->act);

0 -> 2G / GSM
2 -> 3G / UMTS / UTRAN
7 -> 4G / LTE / EUTRAN

Edit: I just remembered that I also have a SIM7000E. I get the same result; it connects fine to 4G with automatic provider selection.

Thanks
Felix