NRF5 SDK MQTT using external GSM/GPRS module

[CodeLoader]

Hello there,

We are planning to use MQTT and nRF5 boards in the project. We've successfully tested out MQTT examples provided in the SDK using BLE router on Raspberry Pi.

However, we would like that our devices communicate with the broker not through 6LoWPAN over BLE, but rather through an external GSM/GPRS module like Quectel UC20, which would be connected to the nRF via UART, so that Raspberry is not needed and everything is on the board. 

As far as we've seen. the Nordic MQTT library doesn't allow to set up your own transport layer. We still want to use the library to do the dirty work on encoding/decoding MQTT messages and sending us events, but with another transport channel. We also need to use TLS-PSK functionality.

Could you suggest us the way we could implement it without messing up with the lower layers of the SDK much? Perhaps we could tweak and rework some files, but we don't know how to approach that.

[Vidar Berg]

Hello,

I not familiar with this modem, but it seems like you can use our MQTT library and create a new mqtt_transport_xxx.c file to interface your IP stack. The function pointers for the transport functions are declared in mqtt_transport.c.

[CodeLoader]

Thanks! That's what we have also found out to be the most appropriate solution - replace mqtt_transport_lwip with our own transport layer