GSM/3G module as interface for lwip

[JimmyPedersen]

Hi
Is there anybody here that has implemented an lwip interface to a UART connected GSM/3G module that is willing to share some code or at least insights in how to do it? Assuming the elected GSM/3G module has own IP stack.
The goal is to be able to communicate with AWS IoT (using MQTT w. TLS) over either WiFi, ethernet or GSM/3G module.
Kind regards
/Jimmy

[ESP_Angus]

There's no official support (at least not yet) but this pull request on github adds PPP over serial support for a GSM modem, with an example:
https://github.com/espressif/esp-idf/pull/272

Angus

EDIT: I missed the GSM module "has own IP stack". This is a little tricker, as you'd either need to slot in at the mbedTLS level (assuming IP but no TLS) or to somehow integrate into the AWS SDK network layer, if the GSM module does TLS. PPP is probably the easiest way to integrate.

[JimmyPedersen]

Thanks for the quick reply Angus.
I assumed that the GSM/3G module having it's own IP stack would simplify things but thinking about it might not.
Either way it's still possible to use PPP on just about all modules that support data as far as I know.
The PR you sent looks interesting for sure, at least as a beginning, since I need GSM/3G as well as Ethernet (WiFi is actually just a bonus in this application). This means the use of 3 interfaces as far as I understand.

When you release the Ethernet example I assume it uses it's own interface so that it can be used simultaneously with Wifi, am I right?
Btw. any ETA of the release?

Anyone out there implemented a PPP lwip interface?