HL78 Periodic-TAU


When I configure the PSM Periodic TAU with the +CPSMS command, the network can modify the requested periodic TAU with an other value.

In the documentation, we can’t normally have this Periodic TAU value in the event “+CEREG: 4”.
But it was always empty:

+CEREG: 1,“0001”,“01A2D001”,7,“00000011”,
+CREG: 1
+CEREG: 4,“00000011”,
+CREG: 4

So how do you know the real periodic TAU used when the modem start the PSM ?

how did you enter for +CPSMS?
It should be something like this:

14:29:15.501 on 08-Mar-2021> AT+CEREG=4
14:29:15.534 on 08-Mar-2021> 
14:29:15.713 on 08-Mar-2021> OK
14:29:15.725 on 08-Mar-2021> 
14:29:15.815 on 08-Mar-2021> +CEREG: 0
14:29:15.827 on 08-Mar-2021> 
14:29:15.838 on 08-Mar-2021> +CREG: 0
14:29:15.849 on 08-Mar-2021> 
14:29:15.877 on 08-Mar-2021> +CEREG: 2
14:29:15.887 on 08-Mar-2021> 
14:29:15.895 on 08-Mar-2021> +CREG: 2
14:29:15.906 on 08-Mar-2021> 
14:29:16.93 on 08-Mar-2021> +CEREG: 1,"0001","01A2D001",7,,,"00001010","00111001"
14:29:16.137 on 08-Mar-2021> 
14:29:16.145 on 08-Mar-2021> +CREG: 1,"0001","01A2D001",7
14:29:16.197 on 08-Mar-2021> 
14:29:17.279 on 08-Mar-2021> +SIM: 0
14:29:17.288 on 08-Mar-2021> AT+KSLEEP=1,2
14:29:17.556 on 08-Mar-2021> 
14:29:17.564 on 08-Mar-2021> OK
14:29:17.573 on 08-Mar-2021> AT+CPSMS=1,"11100000","11100000","00111001","00001010"
14:29:19.670 on 08-Mar-2021> 
14:29:19.682 on 08-Mar-2021> OK
14:29:19.695 on 08-Mar-2021> 
14:29:46.160 on 08-Mar-2021> +CEREG: 4,,,,,,"00001010","00111001"
14:29:46.180 on 08-Mar-2021> 
14:29:46.214 on 08-Mar-2021> +CREG: 4


My CPSMS command are


+CPSMS: 1,"11100000","11100000","10000010","00000011"

+CEREG: 1,"0001","01A2D001",7,,,"00000011",

+CREG: 1

+CEREG: 4,,,,,,"00000011",

+CREG: 4

And my firmware version is 4.6.8

Your setting:

Requested extended periodic TAU (T3412) value: one minute
Requested Active Time (T3324) value: 6 seconds

Probably it is too short for both values, as a result, your network did not accept that.

Precisely, these values are to have modifications on the TAU on behalf of the network.
The network adds between 40 and 50 minutes to the requested TAU.
The HL78 receive from the network this TAU value, because he sleep between 41 and 51 minutes.

So my question is : If the HL78 sleep during the network TAU value, how i could retrieve this value ?

I’ve try other TAU value greater than 45 minutes, but the “+cereg: 4” message is the same !

Based on my experience, if you set too small, the returned value will be missing…

Probably you cannot let it sleep until you get the response

I’ve try with your PSM value


It’s working, but when I set lower value, the PSM work fine with no value in +CEREG message !
Strange !!!

I guess it is using the old value of +CEREG