Bizzare AT command problem on GPRS Modem

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timbo767

3 posts

Wannabe Geek

Topic # 5614 12-Nov-2005 00:41

Hi,
Trying to connect to Vodafone AU via laptop and gprs mobile. Connectivity between laptop and phone not an issue, can talk to modem through hyperterminal and send sms's, and do all the usual AT commands.

I can use ATDxxxxxxxxx to dial any number, which works and rings through with no problems. The problems start when I want to dial ATD*99# to initiate the GPRS connection.
ATD*, ATD*9 both work, it attempts to dial and then fails with no carrier, but atd*99 fails with ERROR.

atd*99#
ERROR
atd*
NO CARRIER
atd*9
NO CARRIER
atd*99
ERROR

This makes no sense to me and has me completely stumped!! Why would atd*9 work but not atd*99?
Open to suggestions from anyone more enlightened than myself.
Thanks!
-Tim

freitasm

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Reply # 23055 12-Nov-2005 09:02

Welcome here Timbo... How are you connecting these? Via cable, Bluetooth?

Also, try doing ATZ; first, then ATDT*99#. You can then try ATDT*99***x# where x is a number 1 through the number of GPRS connections configured on your mobile.

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freitasm

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Reply # 23056 12-Nov-2005 09:03

Also, wouldn't be easier to have this as a modem? The GPRS connection is easier to establish if the phone is configured as a modem, with the proper drivers. If using Bluetooth you should really use the DUN connection (which will be just another dialup).

But let us know what model and connection type you have.

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barf

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Reply # 23119 13-Nov-2005 16:27

freitasm: It is a modem already! RFCOMM modems (thats the serial protocol phones use with both IrDA & Bluetooth) need no special drivers. Any self-respecting GPRS phone has it's own PPP stack and simple AT commands are used to initiate the GPRS connection. DUN is just Windows' name for a PPP dialer.

timbo767: What type of phone do you have? try the AT commands freitasm suggests. Else try to set a 'default profile' or something similar in the GPRS settings in your phone.

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freitasm

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Reply # 23126 13-Nov-2005 18:45

What I mean is that if using over serial sometimes a modem driver helps in managing the phone. And if using Bluetooth the DUN service is ready to go - simply enter the dial number, username and password in the dial-up dialog that shows up when establishing a connection.

There must be something else, since timbo is trying to use Hyperterminal...

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Reply # 23129 13-Nov-2005 19:23

Forgive me, for I must correct you freitasm.

In the case of GPRS the "DUN" service you see when looking at a Bluetooth (or IrDA) device's features is no different to a serial connection to the phone, in fact it is exactly the same thing: thats why timbo is using hyperteminal to find out what is wrong. Windows (which sucks) abstracts this and makes it appear to be some extra feature.

What DUN does is open a terminal emulation connection to the phone (like hyperteminal) and send AT commands to make it 'dial GPRS'. When DUN sees "CONNECT" returned from the modem it invokes a PPP client (it probably says "verifying username and password" at this stage) and the point-to-point protocol negotiates an IP for your PC aswell as setting default network routes. if DUN sees anything else returned from the modem it'll give you a typical, vauge error message.

I dont use windows so you are more qualified than me to say this could be a driver problem.

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freitasm

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Reply # 23135 13-Nov-2005 20:46

Hmmm. Nope, DUN is a Bluetooth profile, not a specific Windows feature. DUN is available as a service in mobile phones, Windows PCs with a modem. Clients with the DUN profile can then use the DUN service.

While in essence it is a serial connection with the commands send down the pipe, it actually is a separate profile on Bluetooth, with specific controls. Check the Bluetooth specification - forget the fact that a Windows machine is involved.

Using the DUN features makes the connection easier. But using Hyperterminal makes it easier to debug configuration problems, although I haven't come across a connection via DUN that needed anything but the dial number (*99# for GPRS/UMTS or #777 for CDMA) and perhaps a init string).

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barf

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Ultimate Geek

Reply # 23137 14-Nov-2005 00:03

yes I know that DUN is a Bluetooth profile seperate from the serial profile but, I still think Windows sucks and that I am entitled to my opinion.

:-) Sorry for being off-topic I wont post unless its relevant

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timbo767

3 posts

Wannabe Geek

Reply # 23139 14-Nov-2005 05:47

Hi again folks,

Thanks for your replies.

For your information im using a sharp GX25 on vodafone AU talking to my laptop using a bluetooth encapsulated serial link. As the serial link is working fine and has managed to get me this far I dont see in *theory* how it could be anything other than an issue with the command set on the gprs phone... however the plot thickens!!

I previously tried ATZ, ATDT, and everything in between, and actually managed to get it to do something by inserting a space in the dial string, so instead of atd*99#, atd* 99#.

This returns the code +CUSD:2
then ERROR

This (from gsm spec) means the folowing...

USSD (unstructured supplementary service data) Terminated by network

AT+CEER returns an unspecified GPRS error
Have played with GPRS profiles on the phone with no luck.

Any Ideas??
Thanks guys! Any ideas are greatly appreciated.

timbo767

3 posts

Wannabe Geek

Reply # 23480 18-Nov-2005 00:34

Hi again all,

Managed to solve this one... still doesnt make too much sense though!

I was trying to initiate the GPRS connection while the phone was in 'PC software' connectivity mode. After leaving bluetooth enabled and the phone idle it had no further problems, AT commands (including at*99#) all worked properly.

Maybe it couldnt initialise the ppp stack/gprs profile in this mode? Weird. Still doesnt explain the half functional AT command set. Hope this may be of assistance to others in the future!

Still have an issue with LCP being terminated on connection but as the ppp seems to authenticate with no problems im pretty sure its unrelated.

Thanks for all your help,
-Tim

barf

643 posts

Ultimate Geek

Reply # 23531 19-Nov-2005 12:24

I had a similar PPP disconnetion problem with my T610 over IrDA

Assuming you use Linux, in the /etc/ppp/options file comment out the following two lines:

#lcp-echo-interval 30
#lcp-echo-failure 4

It seems pppd defaults to sending an LCP echo-request frame to the T610 (which it ignores). After 4 unsuccessful attempts, pppd destroys the connection.

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