Motorola T191 GSM interface with C52

[hi52]

Hi,

I have one T191 mobile phone. I have follow the instruction
http://pinouts.ru/CellularPhones-A-N...1_pinout.shtml
http://forum.gsmhosting.com/vbb/arch.../t-460885.html
http://pinouts.ru/images/cable_cell2.gif
but still can't work.

I have using Hyperterminal to simulate. The Hyperterminal configuration is..
Baudrate: 9600 (and also try other baudrate 1200/4800/19200)
Data bits:8
Parity: None
Stop bits: 1
Flow contal: None
and i tick all the ASCII Setup included the Line delay is 450 and Character delay is 450
I have short the 2.5mm jack pin L(Tx) and R(Rx) then type something on Hyperterminal it would show the echo character.

After configured and test the cable, I try to type AT but the Hyperterminal no respond, by rite the phone should reply back OK, am i rite?[?]

Please anyone can help me?

Thank you,

[Binu]

did you make your own data cable or do you use the standard cable.
There will be some electronics inside the cable which is used to convert the TTL to RS232 logic. This electronics circuit need power and it will get it through the RTS & DTR pins of the data cable.

You have to enable the RTS & DTR pins. Here's the circuit diagram of the data cable.

[hi52]

Dear Binu,

OMG...Ya, i made my own data cable.
The Tx and Rx data pin i direct connected to the mobile phone and no using 3V3 Zener Diode. Would spoil phone not?
I have using MAX232 and I?m using external +5v to supply the IC.

[hi52]

Dear Binu,

Thank you very much. Finally the phone able to reply OK after the AT is type. I was worry my phone is already spoil.

Please can you guide me how to use AT command? May i know is it the AT command is standard command for all the mobile phone included T191? I have refer Telit (
Document: SMS handling[1].pdf ( 56428bytes ) )sample AT command but not sure can support for T191 not..Like example i type AT+CMGF=1 then i get the reply is ERROR! Another example AT+CSCA?<enter> still get a ERROR reply. [?]

Actually how the AT command work? Is it Motorola T191 command is different?

Please advice..
Thank you,.

[Binu]

since AT+CMGF=1 is giving error, i think you mobile wont support Text mode.
To know which modes it support send AT+CMGF=?
if you get reply +CMGF: 0 then the phone will support PDU mode only.

AT commands is common for all modems/mobile.

[hi52]

Dear Binu,

I have try AT+CMGF=? command still reply the error message.


What command we can test somemore?

Thank you,.

[Binu]

put the echo off and try this command
AT+CMGF=0

[hi52]

Dear Binu,

Currently my circuit connection show bellow:

Now my phone not sure what's the problem already.. Can't reply any more already..

Pass 2 day still can work one but also sometime can received the reply and sometime not. Until yesterday...totaly no reply anymore.

Is it my circuit spoil the phone 232 port already? I'm using 10uF cap and the red square box point is connected to Vcc, as your reference circuit is connected to GND. At the beginning MAX232 pin9 and pin10 was not connect Zener 3.3V but now i have add the Zener already.

Is it because we have to use 0.1uF cap for MAX232? Can i use 104 non-polarity cap for replace 0.1uF? or is it we have to use have polarity type 0.1uF cap?

How to check the phone serial port is fine?

Please advice..

Thank you,.

[Binu]

Yes capacitor at pin 2 should connected to Vcc, your circuit is ok.
The zenor diode is must, it forms a 3.3v regulator so ir wont allow voltage greater than 3.3v.
Check your phone with some ready made cable.

[hi52]

Dear Binu,

Very happy to received your reply. Thank for your reply.

Ya, now i have wire up 2 circuit. One is using Zener diode 3.3V and the 2nd one is between MAX232 with phone pin Tx and Rx have a buffer call MC14050BCP. The output buffer is 3.3V because the IC VDD supply is 3.3V from regulator.

Both circuit still can't work..

I don't have the original cable. That's why i do the cable and the rs232 driver.

Now i get more worried already...

Please advice..

Thank you,.