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problem is sending sms with 8051 by siemens C55

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Moderators: Ajay, Junied , abbas1707, Arun Kumar V, pdi33, Shailesh NAYAK, ۞ TPS ۞, shyam, sashijoseph

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cllunlu

Wed Apr 23 2008, 02:54AM

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I am not using data cable.And ı know siemens c55 pin configuration.

celalunlu

cllunlu

Wed Apr 23 2008, 03:01AM

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my cellphone is siemens c55
and pin configuration is:

http://pinouts.ru/CellularPhones-P-W/siemens_c55_pinout.shtml

where is DTR?

celalunlu

Ajay

Wed Apr 23 2008, 03:41AM

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as you said u are connecting it to c55 directly then there is no need of DTR.. just direct connection with tx, rx and gnd.

Did you try what i said? did you make changes in program?

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cllunlu

cllunlu

Wed Apr 23 2008, 06:07AM

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ok.I changed my program.You said me change 'O' and 'K' replaca 'o' and 'k'.I did but I havent tried yet.I will try soon.Thnks for everything

celalunlu

GioppY

Wed Apr 23 2008, 07:47AM

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You have to buffer, or add a pull up resistor to P3.1.
Also led design is wrong.
8051 family has open drain output stage with a weak pull up.
The cellphone rx pin never see a high level.
Regards

cllunlu

Thu Apr 24 2008, 03:03AM

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hi gioppy.
I didnt understand you.
You said "add a pull up resistor to P3.1"
I have done already it.After that "led desing is wrong"how?

8051 family has open drain output stage with a weak pull up.
The cellphone rx pin never see a high level.

can you explain them more?

celalunlu

Ajay

Thu Apr 24 2008, 08:17AM

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did you test what i said?

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GioppY

Thu Apr 24 2008, 08:19AM

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I do not see any pull up resistor in your schematic.
The 8051 port pin can sink 1.6mA (3.2mA for port 0) and source 60uA.

When used as outputs, all port pins will drive the state to which the associated SFR latch bit has been set.
When a 0 is written to a bit in port the pin is pulled low (0).
When a 1 is written to a bit in port the pin goes into a high impedance state.
Only the internal (weak or medium) pull the pin up.

http://www.freewebs.com/maheshwankhede/ports.html

Atmel at89c51rc2 doc4180.pdf
Pag.13 Port type
Pag.107 Electrical characteristics

Regards

cllunlu

Thu Apr 24 2008, 07:28PM

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thnks gioppy.Can you make a right schematic for my project .Please...

celalunlu

sashijoseph

Thu Apr 24 2008, 09:46PM

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In your schematic just add a 10k resistor between Vcc and P3.1......that's your pullup.
Like Gioppy suggested your LED's are sourcing current from the 8051 which is bad...they should be made to sink current into the 8051.Look at the attached ckt..

And have you tried out Ajay's suggestion?Please confirm..