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khawer102
Joined: 14 Mar 2006
Posts: 9
Location: Pakistan
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ckielstra
Joined: 18 Mar 2004
Posts: 3680
Location: The Netherlands
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 Posted: Thu Mar 30, 2006 4:17 pm |
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| The document you refer to has many cable schematics. Just to make sure, did you use the DB9-DB9 scheme of page 1 or page 2 ? |
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Donlaser
Joined: 17 Sep 2005
Posts: 12
Location: Trenque Lauquen, Argentina
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| Posted: Thu Mar 30, 2006 7:34 pm |
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what modem are you using?
I my proyects with motorola G20 GSM modem i need to connect some of the RS232 modem hardware handshake lines together to get it work...
Most modems use a hardware handshake protocol, you need to control or loop togheter the handshakes lines.
http://www.airborn.com.au/rs232.html
In this page you find how to loop together the handshake lines. |
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zvasas
Guest
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| Posted: Fri Mar 31, 2006 2:13 pm |
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| If you using siemens try 19200 Boud rate. |
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khawer102
Joined: 14 Mar 2006
Posts: 9
Location: Pakistan
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| Posted: Sat Apr 01, 2006 11:40 am |
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i am using DB9 to DB9 scheme of page 2.
i am using enfora's gsm modules. you guys can take a look at them at
www.enfora.com
can you guys please make it clear, when do i require loop together. |
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ckielstra
Joined: 18 Mar 2004
Posts: 3680
Location: The Netherlands
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| Posted: Sat Apr 01, 2006 3:25 pm |
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| Quote: | | i am using DB9 to DB9 scheme of page 2. |
Looks like a decent null-modem cable.
What logic levels are you applying to the DSR and CTS output pins of the PIC side of this cable?
Debugging RS-232 problems is always a bit difficult. A lifesaver to me has been the use of a breakout box with LEDs showing the signals on each line. Make sure to get yourself such a device. As you have a working setup when connected to the PC you can compare the differences in LED readings for the two setups. |
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khawer102
Joined: 14 Mar 2006
Posts: 9
Location: Pakistan
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| Posted: Sun Apr 02, 2006 2:31 pm |
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| where can i find this breakout box, i dont think my university labs have one with them. but i suppose i can also use an oscilloscope for the same purpose. is it possible that i have a max232 chip in my modem. |
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arunb
Joined: 08 Sep 2003
Posts: 492
Location: India
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| Posted: Mon Apr 03, 2006 7:56 am |
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Hi,
Check the voltage levels in the RS 232 port, it is possible the level detector you are using cannot detect the change in the level, I had a similar problem once.
The hardware worked well with my dekstop PC but it did'nt work with a laptop, I then found the voltages to be +/- 5.
Just a thought..
thanks
arunb |
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frustrated
Guest
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| Posted: Sun Apr 09, 2006 7:15 am |
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i know can send my sms messages but how can i receive them do i read the 3 strings in first. can any one with some experience in this area give some advice?
Thanks |
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