I bought USB modem Nokia 21M (usbid: 0421:0638) and I have a problem
running it on OpenWRT on TP-Link TL-WR1043-ND. Firstly modem shows up
as CDROM drive. I run "eject" on this drive and then cdc-acm interfaces
appears. I can initiate ppp connection on the first interface.
Interface ppp0 shows up for few seconds, and then USB disconnects.
Sometimes when ppp0 is alive, device is not disconnecting for a long
period, but on first use of ppp0 (i.e. ping 184.108.40.206) its immediately
Three seconds after USB-disconnect, device shows up once again, but now
it shows up as SINGLE cdc-acm interface, and this interface is not
fully functional. I can chat with it, but for most AT-commands
it responds "ERROR". It responds "OK" on "AT", but "ERROR" on "ATZ",
I tried connecting modem with powered or unpowered USB HUB, both
"full speed" and "high speed" - no effect - modem disconnects
(modem alone, not USB HUB).
I tried with two SIM cards, from different providers.
But this pattern does not repeat on my Linux notebook (I achieved
this effect only once in many attempts; Slackware 13.37, tried with kernels
2.6.37, 3.1, 3.2), regardless through HUB or not.
I measured current consumed by modem, when working OK with notebook:
about 260mA. Then I measured current consumed by Huawei E220 which work
OK also on my router: 330mA (with other SIM-card; but further i placed
that SIM-card in Nokia Modem - obviously with no effect).
So, maybe its not current shortage nor SIM-card problem...
I looked at voltage with oscilloscope - when modem connected to router without
powered HUB, voltage can drop a little below 4.70V, but with powered
HUB voltage stays in a range 4.90-5.30V - the same range as when
modem is connected to my notebook. Unfortunately, I have no lab power supply.
I tried with OpenWRT trunk r30543 with my bloated configuration (kernel 3.2),
another trunk version with bloated configuration and 2.6.39 kernel,
and OpenWRT 10.03.1, precompiled image from OpenWRT downloads +
installed only kmod-usb-acm and chat.
pppd commandline (I know, some options are useless here, but this works on notebook):
/usr/sbin/pppd /dev/ttyACM0 921600 connect "chat -V -f /tmp/chat.aero2" crtscts -detach defaultroute usepeerdns noauth debug persist noipdefault
What else can I try to solve this problem?