How to change eDRX value for asset tracker application

[andrew926]

I have a Thingy 91 and try to analyse the PSM and eDRX in asset tracker application. I use NCS 1.4.0 in this case.

In prj_thingy91_nrf9160ns.conf file I found the settings for periodic TAU and active time (CONFIG_LTE_PSM_REQ_RPTAU, CONFIG_LTE_PSM_REQ_RAT), which are set to "00000110" (60 minutes) and "00000010" (4 seconds) respectively. But there is no setting for the edrx value.

When I send the command "AT+CEDRXS?" in Link Monitor, I get the response "4, 1001", which indicates the edrx value is 163,84s. Where is this value set in the application files?

And when I count the seconds the device is in RCC Mode: Idle, I get 10 to 20 seconds, which by far misses the expected 163,84s. PSM is disabled through SES -> Project -> Configure nRF Connect SDK Project... -> menuconfig -> Asset Tracker -> Device and modem -> Enable power optimization (no tick). 

[Stian Røed Hafskjold]

Hi,

The AT+CEDRXS command is used to set the eDRX interval. So when you read out this value, you will only get the requested value which may not match the value given by the network.

https://infocenter.nordicsemi.com/topic/ref_at_commands/REF/at_commands/nw_service/cedrxs_read.html?cp=2_1_7_3_1

To read the value given by the network use the AT+CEDRXRDP command:

https://infocenter.nordicsemi.com/topic/ref_at_commands/REF/at_commands/nw_service/cedrxrdp_set.html?cp=2_1_7_4_0

The asset tracker application is not an easy starting point, and I would recommend to use the UDP sample instead, it is designed so that it is easy to change the eDRX and PSM parameters, setup a data upload interval, and do current measurements:

http://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/samples/nrf9160/udp/README.html#

Here is the code that updates the eDRX interval:

https://github.com/nrfconnect/sdk-nrf/blob/00cceb9a17da9a8f33b5a48cb179bc2ab8f85325/samples/nrf9160/udp/src/main.c#L67

[andrew926]

Hi Stian,

thanks for the reply. So the lte_handler function handles the events which are initiated by the AT commands or by the network.

I am still wondering why the requested edrx value is "1001", I can't find the value anywhere in the code or conf files. Is "1001" the default value for edrx?

AT+CEDRXRDP returns "" for the network-provided edrx value. What does it mean?

[andrew926]

I contacted iBasis and they said that eDRX feature is currently not supported in Germany with iBasis.