HL7692 2G Connectivity Issue

IoT Modules Legacy HL Series
1

Hi,
I am using the HL7692 modem and I connect it to a 2G (GSM) operator, communication can’t seem to be established correctly. A TLS session should be opened after the SIM replies, however this never happens. When using a 4G operator, communication can be achieved without any issues. I’m using AT commands on a mangOH Green board.

AT Commands used:
AT+KSRAT=1
AT+WDSS=0,“JTM2M”
AT+WDSS?
AT+COPS=?
AT+COPS=0,2,“23415”,0
AT+COPS? (Verifying that I have successfully connected to a 2G network)

These responses are received after necessary commands are completed:
+STKPRO: 19,"",0,0
+STKCNF: 64,32,2,145
+STKCNF: 39,0,255,144

I also tested 2G connectivity with a WP7607 module which was successful using the same methods and environment as above.

Any help would be appreciated.
Thanks

2

Hi PMcC,

Could you kindly provide the full AT log (2G network) with HL7692 and WP7607 to undertand the test case?

3

Hi Sierra_klin1,
Thanks for your reply. See below full AT commands used for each test (The AT commands had to vary slightly to cater for the different modules e.g. +wdss and +cgdcont for setting APN):

H7692 4G Test.txt (1.8 KB)
HL7692 2G Test Fail.txt (531 Bytes)
WP7607 2G Test.txt (855 Bytes)
WP7607 4G Test.txt (822 Bytes)

4

HI PMcC,
For HL7692, maybe you need to check APN settings of AT+CGDCONT? for 2G and 4G case.

5

Hi Sierra_klin1,
I have been using the same +CDGCONT details in both cases of 4G and 2G, I even tried different details from the WP7607 case also. Unfortunately this is still not working. Does the HL7692 module properly support 2G as I have found the below in the AirPrime HL76xx AT Commands Interface Guide

image
image.png1323×1026 62 KB

6

Hi PMcC,

HL7692 does support LTE Cat-1 (B3, B8, B20), GSM Band 900MHz and 1800 MHz.
The +CDGCONT support GSM as well.

I don’t know how your postman inits the connection with HL7692.
When HL7692 in 2G mode, I don’t know if you need to activate the PDP manually by AT+CGACT=1,1 to get the local IP address (Check IP by AT+CGPADDR=1).

7

Hi Sierra_klin1,

I have managed to solve this problem. It was down to a serious delay of 12 minutes for a TLS session to be opened using the HL7692 on 2G. However when doing this exact same operation using the same connectivity parameters on a WP7607 it takes 2 minutes to open a TLS channel. See below connectivity settings for each module. Is HL7692 supposed to be slower than WP7607?

HL7692 2G Connectivity.txt (160 Bytes)
WP7607 2G Connectivity.txt (131 Bytes)

8

Hi PMcC,

Good news that you manged to solve this problem.
Regarding the 12minutes delay, I cannot tell the exact reason without traces. But I guess some difference of retry mechanism when problem with the PDP activation or TCP communication.

9

Hi Sierra Team,
Can we have a follow up on this issue ? Can you attempt a reproduction Within Sierra Wireless Labs ?
This is affecting a smart meter customer using HL7692.
Thanks,
Loic

10

Hi Loic,

Sorry I may not understand your test case.
Could you let me know how to make the test?
Where you can see the 12 mins to make the TLS session?

For a normal HTTP with SSL test, it only takes me 5s to get the result.

ATI3
AT+KSRAT=1 //2G only
AT+COPS?
+COPS: 1,2,“46000”,0
AT+KCNXCFG=1,“GPRS”,“cmnet”
AT+KCNXUP=1 //21.03.2019 14:29:12.360
+KCNX_IND: 1,1,0 //21.03.2019 14:29:14.254
AT+KHTTPSCFG=1,“httpbin.org”,443,0,0, 1 //No authentication, only encrypt data
AT+KHTTPSGET=1,"/" //21.03.2019 14:29:24.001
CONNECT
HTTP/1.1 200 OK //21.03.2019 14:29:39.414. Only 5seconds to get the result.
Access-Control-Allow-Credentials: true
…