FS#115 - WWAN-connections using 3g with HUAWEI ME909u-521 unstable

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
45/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Quiet
Tech stack
shell
Domain
embedded-iot, networking

Research direction

Start with /lib/netifd/proto/3g.sh and /etc/gcom/setmode.gcom, then compare the ME909u-521 AT command specification with the current Huawei mode-setting command. Reproduce the failure with the modem and inspect how the script handles the command's exit status. Done means the relevant modem mode-setting path behaves correctly without regressing simpler Huawei modems.

Written by the indexing model from the issue text.

Description

flyspray

reinerotto:

Actually, I am trying to stabilize wwan (3g actually; LTE later on) using pppd with my HUAWEI ME909u-521,
because either my MT7620-based router locks up during boot already; or after short period of real usage.
During night, when router is almost idle, just some watchdog date sent via wwan, no problem.

First trace of a possible problem was this msg in logread:
daemon.notice netifd: wwan (1676): Error setting WWAN mode!

Wich is expected, as in /lib/netifd/proto/3g.sh:

...
elif echo "$cardinfo" | grep -qi huawei; then
case "$service" in
umts_only) CODE="14,2";;
gprs_only) CODE="13,1";;
*) CODE="2,2";;
esac
export MODE="AT^SYSCFG=${CODE},3FFFFFFF,2,4" #####Will not work !!!!! Switching USB-Stick to 3g-preferred ?
...
...
[ -n "$MODE" ] && gcom -d "$device" -s /etc/gcom/setmode.gcom

Will not work, because the ME909u-521 rejects AT^SYSCFG . However, AT^SYSCFGEX will work, but having different syntax.
MODE="AT^SYSCFG=${CODE},3FFFFFFF,2,4" will be effective for simpler modems.

/etc/gcom/setmode.gcom returns exit 1; but this error is not checked in 3g.sh

Not shure, whether this is the reason for my problems; however, reason of concern, as high speed modems
are more and more common.
Willing to participate in testing/debugging.

For details regarding my modem, consult
HUAWEI ME909u-521 LTE LGA Module AT Command Interface Specification
http://www.paoli.cz/out/media/HUAWEI_ME909u-521_LTE_LGA_Module_AT_Command_Interface_Specification-V100R001_02.pdf

Dominant language
C
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