Advice on how to proceed with my nRF9160 project

[PVH]

I am just getting started with the nRF9160 DK. I have a few questions, and I have searched the DevZone for answers, but I am still a bit confused and unsure how to go on with my project.

I have not worked much with wireless technologies before, especially not LTE-M or other mobile data technologies. First of all, I would like to program a simple application that would send small amounts of data to a HTTP server. I also need to access the GNSS module.

So far, I have two ideas on how to achieve this (all using the proprietary LTE-M modem firmware):

1) Flash the Serial LTE Modem sample as the application firmware and use another microcontroller to communicate with the nRF9160 through just an UART connection. My own application firmware would then be on the external microcontroller.

2) Write a custom application firmware for the nRF9160 DK using Zephyr and connect to the modem firmware using nrfxlib.

But, what I think I really would like to do is this:

3) Write a custom application firmware in a bare metal fashion, that can control the proprietary LTE-M modem firmware using, for example, an internal UART connection or similar.

I understand that 1) might be the easiest way for me to go, but it requires an external microcontroller.

I am a low level kind of guy, and I usually do bare metal programming with little or no use of third-party libraries. I really do not want to learn Zephyr and fiddle with west and other build tools. So I think 2) is basically ruled out.

Option 3) sounds interesting to me, since I would learn a lot about socket programming, TCP/IP etc. - but, I fear that I might chicken out and go with 1) and just add an external microcontroller :-)

However, before I rule out 3) completely, I would like to know how the application part of the nRF9160 can communicate with the modem firmware on the lowest level. For example, is it possible to send AT commands, internally, using one of the UART peripherals? And what about data packets? Can they be transferred through the AT interface as well?

I have looked at the nrf_modem headers and source files included with the nrfxlib, but those files did not answer my questions - only made me more confused.

But, at least I recently found out how to do bare metal programming on the nRF9160:
devzone.nordicsemi.com/.../bare-metal-programming-on-the-nrf9160

Any help or advice is much appreciated. Thanks a lot in advance :-)

[Kazi Afroza Sultana]

Hello, 

The only way to communicate with the modem is through the modem_lib (Modem library — nrfxlib 2.1.99 documentation (nordicsemi.com)). The modem_lib is OS agnostic, however we would highly recommend using NCS. 

For your requirements, sending data through MCU to nRF9160 DK needs custom build environment and that might not be straight forward. So, it is better to use NCS and we can support you much better. Here is the link of the fundamental course on nRF Connect for SDK(NCS) Nordic Developer Academy (nordicsemi.com) you can look at. 

Thanks.

Best Regards,

Kazi Afroza Sultana

[PVH]

Thanks for clearing things up, Kazi :-)

As I understand it, Zephyr is inseparable from, and really a part of NCS? But some parts of NCS (such as the modem library) can work without Zephyr with some extra effort? In the documentation, it looks like I need to implement some functions for memory (de)allocation, among other things - in the section "Porting the Modem library to your OS".

It looks doable, but yes - it might be easier, or at least more safe, to just go with NCS...

However, I actually might need a separate MCU in my application for other reasons, so I will try out the Serial LTE Modem sample very soon and see how it works. Maybe this can help me decide which way to go :-)

[Kazi Afroza Sultana]

You are welcome Peter. Let us know the consequence and if you need further help. 

[PVH]

Thank you :-)