RC7620-1 ATH does not deactivate PDP context

IoT Modules RC76
1

ati9
Manufacturer: Sierra Wireless, Incorporated
Model: RC7620-1
QTI baseline: MPSS.JO.2.0.2.c1.1-00073-9607_GENNS_PACK-1.463040.2.469835.3
Revision: SWI9X07H_00.08.44.07 2539f0 jenkins 2023/04/26 10:17:51
IMEI: 353635111532236
IMEI SV: 28
FSN: CN2335309609B1
+GCAP: +CGSM,+DS

When I terminate a PPP connection I can no longer reconnect. It seems the PDP context remains active even though I issue an ATH command at the beginning of my dial script. Some commands like AT+CFUN will just return ERROR, and the final ATD command ends with ‘NO CARRIER’.

Perms of /dev/ttyS8 are ok, no ‘mesg n’ neccesary.
ATH
OK
AT&F
OK
AT+CFUN=0
ERROR
AT
OK
AT+CFUN=1
ERROR
AT
OK
AT+KSLEEP=2
OK
AT+CCID
+CCID: xxxxxxxxxxxxxxxxxxx

OK
AT+CGSN
353635111532236

OK
AT+CMEE=1
OK
ATE1
OKCalling …
AT+CGDCONT=1,“IP”,“xxxxxxxx”
OK
ATD99**1#
NO CARRIER

Manually testing this and checking with AT+CGACT? show that the PDP context remains active.

+++
OK

at+cgact?
+CGACT: 1,1
+CGACT: 2,0
+CGACT: 3,0

OK
ath

OK

at+cgact?
+CGACT: 1,1
+CGACT: 2,0
+CGACT: 3,0

OK

Originally I used a RC7620 with older firmware for my tests, but this one is no longer available so we had to switch to the RC7620-1 which came with newer firmware. On the older RC7620 the ATH seems to work fine.

ati9
Manufacturer: Sierra Wireless, Incorporated
Model: RC7620
QTI baseline: MPSS.JO.2.0.2.c1.1-00073-9607_GENNS_PACK-1.416077.1.419248.1
Revision: SWI9X07H_00.08.24.02 f90cbd jenkins 2022/03/21 03:47:54
IMEI: 353634110399804
IMEI SV: 19
FSN: 7Q2132315203B1

+++
OK

AT+CGACT?
+CGACT: 1,1
+CGACT: 2,0
+CGACT: 3,0

OK

ATH
OK

NO CARRIER

AT+CGACT?
+CGACT: 1,0
+CGACT: 2,0
+CGACT: 3,0

OK

This issue seems similar to this one although apparently it was fixed in a later firmware version. Maybe the issue returned again in a later version.
https://forum.sierrawireless.com/t/rc7620-pppos-uart-1-ppp-termination-causes-odd-modem-behaviour-requiring-reset-or-por/26323

We only use the UART, the USB connection is not available on our hardware, so I cannot test if it only occurs on the UART.

Instead of using AT!RESET I can also get it working again by first using AT+CGATT=0 and then wait for a ‘NO CARRIER’. The disadvantage of this is that our application uses the same dial script on a range of different devices like the HL6528, HL8548 and even old Wavecom Q2501B/Q2686. Adding a workaround for a specific modem type is something we try to avoid, and we have to make sure it will not cause issues on other modem types.

Does anyone have similar issues with this?

2

then can you use Release 9 if ATH works for you?
https://source.sierrawireless.com/resources/airprime/software/rc76xx/rc76xx-firmware-release-9,-d-,0/#sthash.Y6yiuFbv.dpbs

3

V9 seems to work. The behavior is still slightly different compared to other models, I usually don’t see the ‘NO CARRIER’ response after ATH. Also sometimes the first dial attempt after the ATH fails but it will reconnect on the second attempt.

ati9
Manufacturer: Sierra Wireless, Incorporated
Model: RC7620-1
QTI baseline: MPSS.JO.2.0.2.c1.1-00073-9607_GENNS_PACK-1.416077.1.419248.1
Revision: SWI9X07H_00.08.24.02 f90cbd jenkins 2022/03/21 03:47:54
IMEI: 353635111532236
IMEI SV: 19
FSN: CN2335309609B1
+GCAP: +CGSM,+DS

OK

+++
OK

at+cgact?
+CGACT: 1,1
+CGACT: 2,0
+CGACT: 3,0

OK

ath
OK

NO CARRIER

at+cgact?
+CGACT: 1,0
+CGACT: 2,0
+CGACT: 3,0

OK

We have 100 RC7620-1’s with V9.6 on order. I guess we have to see if we can change that to V9, or we have to manually downgrade them all.