HL7900 – RI not triggered all the time on incoming TCP/MQTT data in eDRX

IoT Modules
21

Regarding the RI pin.
EDRX is working and the cycles are fine, but even though it detects that a message has been received, the pin’s state doesn’t change.

Yes, I’ve contacted them and am waiting for a response, but I’m posting here just in case i might have some information.

(Sorry, I made a mistake in my previous message—I wrote eDRX instead of RI.)

22

for my test, when the module goes to sleep mode by “at+ksleep=1,1,10”, I can see the RI pin toggled when receiving TCP data

23

And we agree that what you’re doing is :

  • You see the RI pin change state
  • You set WAKE-UP (fast)
  • You see the TCP notification, so you call KTCPRCV to clear the buffer
  • You clear WAKE-UP
  • Return to sleep automatically

Is that all?

And are you checking GPIO7? To see if, when the modem wakes up to control RI, it does so on the first wake-up (Does it generally take a while for your message to be received after you send it?)

24

no, i did not check GPIO7, I only check RI pin as mentioned in the beginning of this forum thread.

25

Hi everyone,

I currently encounteering the same issue as Tom explained in the previous conversation.

The Ring indicator doesn’t work when the module entering Lite Hibernate mode with eDRX activated.

It only works for the first TCP packet received. After that, I can see the module wakes up when I send a message, but the RI doesn’t trigger.

Like Tom, I used the same AT commands, the same functionning , but I cannot find the mistake or the problem.

Note : I’m not using Nb-IOT, but LTE-M, maybe could be the cause, although there are no reasons to not working…

26

I’ve done additional tests on this issue and it seems that the problem is not related to the RI itself, but more to eDRX (and also PSM).

In DRX mode (no eDRX / no PSM), everything works as expected:

  • RI triggers correctly
  • data is always received
  • TCP/MQTT flow is stable

image
image951×1684 107 KB

However, when enabling eDRX (same hardware, same AT config, same SIM/network):

  • First message is usually received correctly (RI triggered, data read)
  • Then behavior becomes inconsistent:
    • modem wakes up (visible on current consumption)
    • but no RI trigger
    • no data in TCP buffer (KTCPSTAT=0)
  • Broker shows no pending messages (as if data was already consumed or dropped)

image
image966×1710 179 KB

This suggests that the issue may be related to eDRX behavior and possibly network-side buffering (messages not stored long enough or discarded before PTW).

I’ve seen similar reports on other modems and references in the GSMA LTE-M deployment guide.

Has anyone experienced similar behavior with HL79xx in eDRX or PSM?

I’ve attached the details of my tests.

27

is this only happening in LTE CAT-M network instead of NBIOT network?

28

I don’t have an Nb-iot SIM card to test, sorry.