GSM modem timeout on SMS transmissions

[David Hearn]

Hi,

I’m using sms-utils to send SMS traffic. About 1 out of 4 times I get read timeouts on the virtual serial port /dev/ttyUSB3 when reading the modem response after sending SMS. Below, I put the read into a loop so that if read() returns 0, we will sleep 500ms and try again, up to 20 attempts. Still ln output from the modem; however, the SMS message is received at the number it was sent to. I cqan run the app again, anfd it works perfectly. Very ramdpm.

Log sample below.

Any ideas?

Thanks,

David Hearn

# ./my_sms_main

wrote 4 *ATQ0*

*rote 1 *

wrote 4 *ATV1*

*rote 1 *

wrote 4 *ATE0*

*rote 1 *

wrote 9 *AT+CMGF=0*

*rote 1 *

wrote 9 *AT+CPMS=?*

*rote 1 *

wrote 8 *AT+CPMS?*

*rote 1 *

wrote 22 *AT+CPMS=”ME”,”ME”,”ME”*

*rote 1 *

preparing for send…

sending message to 14146598013

wrote 11 *AT+CMGS=154*

*rote 1 *

wrote 310 *0011000B814141568910F30000A8A0F2F79BAED31BD35677546A16C7E2F6A80EA683E9E4EF375DF742BFDBE597FCFDA6EB5EE2B4FB250ECFD10A72B8DC7EBB752A5D4C17D391C3E5F6DBAD7BD5E7F2D75C9C76EB5EE2B4FB35472BC469B74EA593E9643A71DAAD7B89D36EDD4B9C76BFE668C53C3FD7A97433DD4C37CFCF752F72D9AE7B89D3EED71CAD98E7DD639D4A47D3D96AB5194D37CFBBC7*

wrote 1 **

Read re-attempt 1

Read re-attempt 2

Read re-attempt 3

Read re-attempt 4

Read re-attempt 5

Read re-attempt 6

Read re-attempt 7

Read re-attempt 8

Read re-attempt 9

Read re-attempt 10

Read re-attempt 11

Read re-attempt 12

Read re-attempt 13

Read re-attempt 14

Read re-attempt 15

Read re-attempt 16

Read re-attempt 17

Read re-attempt 18

Read re-attempt 19

Read re-attempt 20

[NOTICE] atcmd.c:atcmd_read:293: read timeout

*ead 1 chars, *

sending message to 14146598013 failed

#

[Jesse Gilles]

Are you seeing this issue with an unmodified version of sms-utils?

[David Hearn]

Jesse,

Yes, the same happens with the original binary. Running as “/usr/bin/sms -d /dev/ttyUSB3 –verbose send -f /tmp/junk 4146598013”, we see the same read timeout from atcmd.c, about 20% of the time:

preparing for send…

[ERROR] phonebook.c:phonebook_list_get:294: listing failed

[WARNING] sms_send.c:do_send:252: failed to get phonebook list

sending message to 4146598013

[NOTICE] atcmd.c:atcmd_read:284: read timeout

sending message to 4146598013 failed

#

The error happens after the PDU is written to the modem, and as I mentioned, the message is received on the handset.

I have also since noticed very similar behavior with pppd. I have a chat script called ‘gsm’ in /etc/ppp/peers correctly configured to use the GSM modem on /dev/ttyUSB3. It also fails a certin percentage of times:

# pppd call gsm

GSM chat

Connect script failed

#

Resulting fro mthe above, we see this in /var/log/messages:

Jul 4 08:41:38 mtcdp daemon.notice pppd[3132]: pppd 2.4.3 started by root, uid 0

Jul 4 08:41:39 mtcdp local2.err chat[3136]: Can’t get terminal parameters: Input/output error

Jul 4 08:41:39 mtcdp daemon.err pppd[3132]: Connect script failed

Jul 4 08:41:39 mtcdp daemon.info pppd[3132]: Exit.

It feels like there’s an issue with the USB device driver. I don’t have another version of the CDP to play with to see if the problem exists unsing a different port.

Thanks

[Jesse Gilles]

Just to be sure, are you only using a particular tty port for one thing at a time? In other words, if you have a PPP link up on /dev/ttyUSB3, you can’t use /dev/ttyUSB3 for anything else while that is active.

[David Hearn]

Yes, that is correct. Only trying to send SMS -or- running PPP at any given time.

Thanks

[David Hearn]

ANy ideas on this? SHould I open a ticket with Multitech support?

Thanks

[Author]

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