Sierra Wireless 750 receive error 512 (+CMGL=0)

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Søren Jacobi
New member
Username: Sorenjacobi

Post Number: 1
Registered: 06-2004
Posted on Tuesday, June 08, 2004 - 06:23 pm:   

We are trying to make the Sierra Wireless 750 card receive about 100 sms messages. It starts up fine, receives some messages (from 3 to 20) and then returns an error. From the log-files it seems like the error occures when NowSMS is sending an AT+CMGL=0 request to the card. Then the card returns an error 512.

In HyperTerminal we have tried to send all the same commands to the modem and then receiving messages, without sending the +CMGL=0 to the modem. Here all the 100 messages was riceived ina steady stream without any errors.

We have turned off the pin security and the modem is sat to send messages directly to the modem. And we are using NowSMS 5.5.

This error seems like the same error Dan had in November: http://support.nowsms.com/discus/messages/1/4029.ht ml

Has anyone fixed this problem? Or is there any way to turn off the AT+CMGL=0 command?
ashot shahbazian
New member
Username: Animatele

Post Number: 3
Registered: 06-2004
Posted on Tuesday, June 08, 2004 - 09:59 pm:   

I've had the same problem. AC750 isn't very stable generally, although it's the fastest modem for sending SMS. If it's critical that you use this particular card for receiving messages, try the following:

Make sure the SIM card's SMS inbox isn't full. AC750 doesn't have internal memory buffer so the messages get stored on its SIM, which slows the card down. Run Watcher and delete everything from the Inbox. Next, you need to make sure that the card is polled continually by NowSMS at all times so the SIM card won't fill up. "Power Down" the card by Watcher before disabling the NowSMS service.

Make sure the Watcher isn't running concurrently with SMSGWS and SMSGWNT - turn it off completely. This won't crash your system, but you'd be receiving some messages by Watcher, some by NowSMS, which is confusing.

Check the card's reception level with Watcher or AT command. It's more stable when the reception is better than -61dbm. If your intention is to use the setup commercially the modem's reception must be in 97-100% range (maximum value returned by +CSQ.) Use directional anntennaes aimed to the nearest tower. Sierra antennae patch cables can be bought off their Website. When using external antennaes, make sure that the computer, cable shield and antennae are all properly grounded at a single grounding point.

Try using "Default" setting for SMS message storage - it worked for me.

Limit the modem's COM port speed to 56K

Another observation: PCMCI modems cannot send and receive messages simultaneously, error rate becomes too great. I used older Ericsson handsets, T39 and R520, which have internal memory thus handling inbound and 2-way messaging very gracefully. They are slow, between 4.5 and 7 sec./msg. compared to AC750 (2.8-3 sec.) and the speed depends on the handset's firmware version. Falcom A3 has got 256K internal buffer and should be receiving messages without a hitch, although I still haven't tried it.

Please let me know which of the above helped solving it.

What I'd be interested in is whether anyone was able to make more than one Sierra AC750 work in one PC.

Bryce Norwood - NowSMS Support
Board Administrator
Username: Bryce

Post Number: 2775
Registered: 10-2002
Posted on Thursday, June 10, 2004 - 01:15 pm:   

Hi Søren,

Using the "Direct to Modem" setting should work best on the Aircard 750.

In this mode, NowSMS sends initialisation commands to the modem to tell it not to store received messages, but to send them directly to NowSMS as they are received. (NowSMS will still poll the modem with AT+CMGL=0 commands, just in case ... as this helps keep some modems from going to sleep ... and it helps deal with quirks in some modems. For example, with one of the older versions of the AC750 firmware, the card would only send received binary messages to NowSMS directly, and we still had to poll for text messages.)

Other than that, I've only noticed 512 errors on the Sierra when the modem has weak signal and loses its connection. If I have the GPRS driver set for auto-connect, I notice an icon on the screen indicating that the GPRS connection was broken around the same time that the 512 error occurs. (Despite the included external antenna, it always seems to me that signal strength on the Sierra Aircard is not as good as with other modems.)

It also may be worth trying the v5.50a patch which just got uploaded yesterday (and a list of what it addresses hasn't been posted yet, just a brief mention in one of the threads on templates for multimedia WAP push). One minor change in this patch is that we are now ignoring errors that are returned for the AT+CMGL=0 command when "Direct to Modem" is set. (But the command is still sent.)

The download is at http://www.nowsms.com/download/nowsms550a.zip

-bn


Bryce Norwood - NowSMS Support
Board Administrator
Username: Bryce

Post Number: 2776
Registered: 10-2002
Posted on Thursday, June 10, 2004 - 01:19 pm:   


quote:

What I'd be interested in is whether anyone was able to make more than one Sierra AC750 work in one PC.




Ashot,

According to Jon Firor, Director, Global Technical Support for Sierra Wireless, the driver will not support this.

They recommend using their external modem, the MP750 instead.

I would encourage you to contact Sierra Wireless technical support, and make inquiries about this yourself. Perhaps if enough people inquire about this functionality they will make some changes in their drivers.

-bn
ashot shahbazian
New member
Username: Animatele

Post Number: 6
Registered: 06-2004
Posted on Thursday, June 10, 2004 - 06:31 pm:   

Bryce

Thanks for clarifying. I spent countless hours trying it, to no avail, just crashed my PC a few times. Sierra never answered my emails. I think I'll just call them.

I'm afraid no COM-port modem would work that fast. A dozen that I tried weren't even close to AC750.

How did you make the card send SMS via GPRS? There's GPRS connection here, and the operator does support SMS via GPRS. Just checking GPRS for SMS access box never worked for me. I think I also tried changing some other settings, then gave it up. I'd really appreciate advise on this.

Thanks for the tip about the "direct to modem" setting. I'm going to try this as I'm having too many errors using PC cards..

I referred not to the external antennae that comes with the card, rather a stationary directional high-gain setup. Having it this way is especially importand when using more than 4-5 modems, as one tower won't handle more than that durig peak hours. At least in this far corner of the world :-))
Bryce Norwood - NowSMS Support
Board Administrator
Username: Bryce

Post Number: 2814
Registered: 10-2002
Posted on Friday, June 11, 2004 - 06:06 pm:   

Ashot,

I've just checked the checkbox for SMS over GPRS, and that was enough.

If that isn't making a difference for you, try adding a setting for the modem of CommandPostInit1=AT+CGSMS=0

That tells the modem that is only to use SMS over GPRS. (The setting that we use for the checkbox only makes GPRS the preferred choice, but allows the modem to fall back to GSM.)

-bn

ashot shahbazian
New member
Username: Animatele

Post Number: 7
Registered: 06-2004
Posted on Saturday, June 12, 2004 - 07:14 pm:   

Okay, thanks! I'll let you know how it worked.

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