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Connecting GSM C55 to PIC question

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biggbob

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schema siemens c55

Hello,

I plan to drive a C55 siemens GSM phone with a pic. The phone is under 3,6 volt, is it necessary to respect this voltage when communicating in RS232 and make run the pic in less than 4 volts ?

If anyone have experience about this, thanks to help.

Regards

Bob
 

I´m using a max232 at 4,3V as interface, but the pic is running at 5V.

really use 2 max232, 1 in the motherboard (also used for the bootloader) and the other as the interface for the siemens so the signal pass trought the 2 IC´s to the phone

the best solution is to use the 3.3 version of max232.
 

C55 to pic

Thanks for the tips. I've found how to do with a 232 and it works well now.
Actually I'm experimenting communications with the phone and a Pic 16F873 and a basic compiler.
All is working as I want but I found difficulties to build SMS in basic because the C55 doesn't work in text mode for SMS but only in PDU mode wich is quite more difficult.
Have you try this ?
Do you think that if communication works with a C55 it does work with others cellular modem equiped ?

Regards

Bob
 

Siemens telephones only support PDU mode for SMS sending / receiving.

Look here:
**broken link removed**

Most GSM modems support text and PDU mode.

regards
 

C55 to pic

Hi C-Man,
Thanks very much for your help. That's exactly what I'm looking for !

Great !

Best regards

Bob :lol:
 

where I can find the instructions to build a cable for the C55
thanks
 

If you have pin description for C55 (and I uppose it i not big problem to find serch siemens site or ask their support team ) you can use this primitive schema .
 

hi guys,

im using nokia 3310 for the same application. i dont want to use the
microcontroller in between but want to retreive the received messages directly to the VB program which is running in a PC. i struct up with the embedding the AT commads in the VB program and also retrieving the entire received messages in the VB application itself.

plz somebody help me in the regard

thanxs in advance
ram
 

hi,
let me tell you that nokia 3310 didn't support the at commands (it use a protocol called (f-bus)
here you will find a lot of inf about that :
**broken link removed**
if you want to use at commands with nokia phones using pc only (not embedded)try to use nokia data suite

hope that help you

Fire in the Wire :sm2:
 

kk_ram2001 said:
hi guys,

im using nokia 3310 for the same application. i dont want to use the
............
ram

Search the sourceforge.net there are ready to use library and soft for SMS sending adapted for different phone types and different alphabet . If I am not wrong project was written in C++ , but may be new projects are added to support VB as well .
 

just use 74ls07 open collector buffer to convert 5V TTL level to MOS(3V) level.
 

1. Can the phone (e.g. C55) accept 5 volts data from a micro? (e.g. normal AT89S52)
2. Can the micro accept 3 volts data from the phone?

I just want some confirmation here ...
 

irfansyah said:
1. Can the phone (e.g. C55) accept 5 volts data from a micro? (e.g. normal AT89S52)
2. Can the micro accept 3 volts data from the phone?

I just want some confirmation here ...

1) you can insert resistors to the lines driving the phone I was succesful using 10K but this is not an "elegant" solution.

2) in most applications the answer is yes but this is also not an "elegant" solution.

It is a good idea to use level converters here.

best regards
 

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