Fastest way to shutdown LTE modem nRF9160

[NelsonGoncalves]

Hello,

I have an nRF9160 development kit and was measuring the time it takes for switching off the modem

when it has an open data connection.

I did it by sending an UDP packet and then switching off the modem. The time is measured by toggling a GPIO pin:

gpio_pin_set(dev, PIN,1);
err = lte_lc_power_off();
gpio_pin_set(dev, PIN,0);

This gives me about 1.6 seconds. Is this value normal ? If I use instead lte_lc_offline() I get similarly high values.

[Didrik Rokhaug]

Hi,

When turing the modem off (CFUN=0, lte_lc_power_off), the modem will detach from the network, which involves signalling, and can therefore take  a bit of time. Especially if you are using NB-IoT or there is bad reception. In addition, the modem will store useful data to flash, which also takes a tiny bit of time.

1.6 seconds doesn't sound too unreasonable.

Setting the modem in flight mode (CFUN=4, lte_lc_offline) will detach from the network similarly to turning the modem off, but it will not store the data to flash. However, it is the detach that takes the most time, so it is not supprising that they take close to the same time.

Best regards,

Didrik