HL78xx PPP port stuck (not responding) when KUSBCOMP=1,1,2,5

IoT Modules HL78
1

we’re using:

HL7800.4.4.14
HL78xx.4.4.14.0.RK_02_01_02_00_101.20200702
2020/07/02 23:50:39
IMEI-SV: 3546160908827509
Legato RTOS: 18.09.4.ALT1250.rc3 2020/03/02 10:50:25
atSwi: 30.00
UBOOT: 01.03
Apps: RKAPP_02_01_02_00_94__31f472b547df5417a8f942dd14d4c8cb9bf65395
MAC: ALT1250_02_01_02_00_91_FW
PHY: 12.50.233970
PMP: 234124
SBUB: 1
SBFW: 1
RPuK: 53F7A48A
FPuK: 139A8E70
RBUB: 0
RBFW: 0

We changed the USB port modes to:
AT+KUSBCOMP?
+KUSBCOMP: 1,1,2,5

With this configuration we could not successfully setup the PPP session with the modem PPP port (/dev/ttyACM1). I tried a lot of different modem/ppp configurations, but it really looks like the port isn’t responding.

As soon as I restore the factory default USB mode config with:
AT+KUSBCOMP=1,1,2,3
AT+CFUN=1,1

everything works well!

is there a know problem with this mode and firmware?

and more importantly, how can I find out about the known problems?
Is there a known problem list or do I have to check the release notes document?

Thanks!

2

any special reason you need to use +KUSBCOMP=1,1,2,5 if +KUSBCOMP=1,1,2,3 already work fine??

3

yes, I wanted to test/try some MAC_VIA_MAP logging stuff…

in the meantime I found: https://source.sierrawireless.com/-/media/support_downloads/airprime/release_notes/airprime---hl78xx---customer-release-note---4,-d-,x---r01,-d-,15a.ashx

which is a pretty good overview on the modem issues per release.