How to manage modem communicatioon ?

[Achevillard]

Hi,

I'm working on a custom board with a nrf9160 µC. This board is powered by a battery and a supercapacitor and my job is to assure the autonomy of the battery.

I would like to limit the modem period of activites to let the scap recharges before a new modem activity.

I have set PSM mode when the modem is sleep. But sometimes, the modem wakes up when I am measuring the voltage of my scap.

Need I to use AT+CFUN=0 or AT+CFUN=4 to deactivate the modem activity ?

Is there another solution to prevent the modem activites without stoping the modem and loosing the advantage of PSM mode ?

Thank you by advance

Antoine

(SDK 1.9.1, modem FW 1.3.2)

[Elfving]

Hello again,

Need I to use AT+CFUN=0 or AT+CFUN=4 to deactivate the modem activity ?

I dont think so, no.

How are you putting it in PSM mode, and what PSM values are you using?

Regards,

Elfving

[Achevillard]

Hello,

Thank you for your answer

I set the PSM value with config

CONFIG_MODEM_PSM_ENABLE=y
#320H tau
CONFIG_LTE_PSM_REQ_RPTAU="11000001"
#10s active time
CONFIG_LTE_PSM_REQ_RAT="00000101"

These values are accepted by the network configuration.

Then I call lte_lc_psm_req(true) before starting the modem.

Regards,

Antoine

[Elfving]

Achevillard said:

These values are accepted by the network configuration.

Okey, and this is something you've checked with eg. +CEREG?

And are you saying that the modem erroneously woke up and made this communication, or that you just don't want it to while you are doing some voltage measurements?

Regards,

Elfving

[Achevillard]

I just don't want to it while I am doing some voltage measurements.

I have got the case sometimes. But I don't know how to reproduce it.

Moreover, when I connect the product in LTE-M mode with an infinite active time, I would like to put the modem in a sleep-like mode state without having to detach from the network.

Regards

Antoine

[Elfving]

Ah I see, so you are actually very happy with your current Tau values, as they can give you 320H without being bothered. Your challenge is to stop the application from still wanting to wake up to use the modem. The network is fine with the app not doing anything.

Am I understanding you correctly? If this is something the app is doing then I wouldn't call it a problem you have issues reproducing.

Regards,

Elfving

[Achevillard]

In the most case, yes, I am satisfied with my current tau values.

But in some case, with a network that don't support PSM, I would like to find a way to prevent the modem to have activities.

In this case, after that I transmit my data through the modem, I got many events from the modem.

When I have no more data to publish through the modem, I thought the modem rests in the DRX state, but I received lots of events RRC_Idle then RRC_Connected.

I would like to prevent these events without set the modem offline or without power off the modem.

Is there a way to do that ?

Regards

Antoine

[Charlie]

Hi Antoine,

Achevillard said:

But in some case, with a network that don't support PSM, I would like to find a way to prevent the modem to have activities.

In this case, after that I transmit my data through the modem, I got many events from the modem.

When I have no more data to publish through the modem, I thought the modem rests in the DRX state, but I received lots of events RRC_Idle then RRC_Connected.

This is as expected if your network support eDRX but not PSM. You cannot achieve the PSM features in a network without PSM support.

The reason you received so many RCC events is due to the short T3324 timer configurationn. User guide (LTE) mentions that T3324 timer can be requested by the UE, however the requested value might not be supported by the network. AT+CEDRXS and AT+CEDRXRDP are corresponding commands to set and check eDRX configuration.

Best regards,

Charlie