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Old 10-23-2004, 08:08 PM   #1
Registered: Jul 2002
Location: Florida
Distribution: Centos, Slackware
Posts: 260

Rep: Reputation: 30
pppd and Airlink Pinpoint CDMA modem woes

Can anyone help me with a problem I am having?

I have a linux-based device connected via serial port to a pinpoint CDMA modem.

I have had this working (about 3 months ago), but now when I try to establish
a ppp connection, I get errors (see below).

Here are the relevant files:

bash-2.05# cat /etc/ppp/peers/airlink
mtu 1024
mru 1024
lcp-echo-failure 0
lcp-echo-interval 0
connect '/usr/sbin/chat -s -v -f /etc/ppp/chat-airlink'

bash-2.05# cat /etc/ppp/chat-airlink
"" "AT"
OK "AT&D0"
OK "ATD#19788"

And here is my command to establish the connection:

bash-2.05# pppd call airlink

And here is the log output:

bash-2.05# tail /var/log/messages


Oct 24 00:24:14 hummer pppd[682]: pppd 2.4.1 started by root, uid 0
Oct 24 00:24:15 hummer chat[683]: send (AT^M)
Oct 24 00:24:15 hummer chat[683]: expect (OK)
Oct 24 00:24:19 hummer chat[1105]: ^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@ ^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@
Oct 24 00:24:55 hummer last message repeated 5 times
Oct 24 00:24:55 hummer chat[1105]: ^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@ ^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@
Oct 24 00:25:00 hummer chat[1105]: alarm
Oct 24 00:25:00 hummer chat[1105]: Failed

The really odd thing is, if I connect to the pinpoint modem using minicom
via /dev/ttyS0 at 115200 baud and issue the AT commands manually, I get
the expected replies,

The differences (of which I am aware) are that I have an ipsec tunnel over
a wireless ethernet link, the GPS output to an IP feature of the pinpoint
modem was enabled, and I'm using a different SBC. We are updating the
firmware on the modem, but is there anything you see here that I am doing
wrong? No I haven't tried connecting to a regular telephone modem via
the serial port, I don't have any of those handy at the moment.

Thanks for any help.

Old 11-09-2004, 11:39 AM   #2
Registered: Jul 2002
Location: Florida
Distribution: Centos, Slackware
Posts: 260

Original Poster
Rep: Reputation: 30
Well ... not too many folks using this device, I guess.

It turns out I was doing everything right, but it just won't
work while the ipsec is running.
After bringing down the ipsec connection, I was again able to
bring up the ppp connection to the modem.
I don't know why there is a conflict there, but there is.

Maybe this extra bit of info will be useful. Maybe someone
reading this will know what the conflict is and tell me how
to work around it -- besides shutting off my ipsec.

Just thought the 40-someodd of you who were curious enough
to read the thread might be interested.



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