nRF9160: How to recover when modem call lte_lc_connect() returns -116.

[GameCodingNinja]

I'm using SDK 1.7.0. Here's how I have the modem code setup.

• Init modem outside of thread loop
• Set modem at+ comman CFUN=1 (start searching for a tower)
• Once +CEREG returns data with a 1, I know I have connected to a tower (+CEREG: 5,1,"8404","02073301",7,,,"00001000","00100110").
• I connect with lte_lc_connect()
• Create a socket
• Send some data
• Close the socket
• Disconnect the modem with lte_lc_offline()
• Set modem at+ comman CFUN=4 (airplane mode)
• Put thread asleep until it's time to send data again.

The above works well and can connect to a tower, send data and disconnect many times over. But once lte_lc_connect() returns -116, it will never connect again and I have to reboot the board. Any idea of how I can recover from this?

[Hakon]

Hello,

But once lte_lc_connect() returns -116, it will never connect again and I have to reboot the board. Any idea of how I can recover from this?

Have you tried just calling lte_lc_connect_async() after receiving the -116 error? I'm not sure that's the best way to handle it, but I guess you can try that.

[GameCodingNinja]

lte_lc_connect_async() calls the same function connect_lte() but without blocking.

On line 668 of file lte_lc.c, it times out on the below line.
err = k_sem_take(&link, K_SECONDS(CONFIG_LTE_NETWORK_TIMEOUT));

This is where err = -116 is generated. Not sure why the semaphore is timing out. I even doubled it from 60 seconds to 120.

[Hakon]

GameCodingNinja said:

err = k_sem_take(&link, K_SECONDS(CONFIG_LTE_NETWORK_TIMEOUT));

Maybe you can try changing it to k_sem_take(&link, K_FOREVER) to stop it from timing out.