Using modem/nrf_modem_lib.h and modem/lte_lc.h

[Fridtjof]

Hello dear Nordic support staff,

I'm working on some legacy code (NCS 1.8.0 in case it's relevant) and see this in the inclusion list of one of the files:

#include <modem/nrf_modem_lib.h>
#include <modem/lte_lc.h>

Functions from both libraries are used to set up the modem and create a connection. I'm new to network code on the nrf9160, but looking at samples and documentation, it seems like using only one of the libraries is enough, where you choose lte_lc if you want more granular control.

E.g, the udp sample uses only lte_lc.h, while the http_update sample uses only nrf_modem_lib.h. I also see that the modem_shell sample uses both. Why?

[Fridtjof]

To illustrate the difference, here are the steps that the udp, modem_shell and http_update samples use to connect. I have reduced the code to only what seems like relevant function calls, and added comments

// Sample UDP

lte_lc_init();
// [Configure low power settings]
lte_lc_connect_async(lte_handler);
// [Wait for lte_handler to give a semaphore before continuing]
// [Do actual network stuff using net/socket.h]

// Sample HTTP Update
nrf_modem_lib_init(NORMAL_MODE);
fota_download_init(fota_dl_handler);
// [optional cert provisioning]
lte_lc_init_and_connect();
fota_download_start();

// Sample Modem Shell
nrf_modem_lib_init(NORMAL_MODE);
at_cmd_init();
at_notif_init();
at_monitor_init();
lte_lc_init();

I just don't see when it is necessary to initialize the modem with one library or the other. Upon closer inspection it seems http_update also uses the lc_lte library in common/include/update.c.