AT command using microcontroller (assembly language)

[good_evil]

Hi, i am hendry from indonesia. I am doing my thesis now and i need some help from you.

I want to ask if it is possible for us to send at command to a selular phone using microcontroller? If it is possible, how can i make the connection between microcontroller and the cell phone? Can AT+Command being execute by serial connection to the cell phone? (because i use assembly language, so it is easier to send data with serial connection).

Thanks.

[S_M_A]

It's possible for sure if microcontroller has an UART interface and the phone also use an UART interface.

[good_evil]

What do you mean by UART interface? Now, i still can not send at command to siemens SL 45. I can send it from computer and the micro also can send the data to computer. But, when i tried to send data to cell phone using micro, it doesn't work...

[S_M_A]

Oh, I assumed that the phone you were using was designed for an embedded environment, i.e. it is equipped with standard UART (RS232 or similar) interface.

I may be wrong here but I have at least heard that some end-consumer phones do not have built in Hayes interpretators. Instead they let the PC provide an UART interface thru a driver that provide the Hayes interpretator. The driver then communicates with the phone using a "private" a protocol.

However, as far as I can tell from http://www.benq-siemens.com/cds/frontdoor/0,2241,hq_en_0_16954_0,00.html (page 71) it seems like this phone do not need anything but a standard modem driver so it should work...

Have you tried to connect a RS232 listener? If you can't build one yourself there is alot of places where cheap listeners are sold. A few google hits: http://www.scancat.com/minitstr.html
http://www.telescopes.ca/hobby/RENDER/0001/2065/3099/11955.html

Maybe also http://www.camiresearch.com/Data_Com_Basics/RS232_standard.html
can be helpful.

[good_evil]

Ok, thanks for your references. I had tried and success to send at+cmgd (for deleting message) to my cell phone. Now, i have another probelm, i sent at+cmgr=1 to read and save the message (with its header) to internal memori of the microcontroller. But, my cell phone sent it too fast, about 62 byte once a time (i tried it with hyper terminal on the dekstop computer). Can you tell me how to make handshaking between the microcontroller and the cell phone?
Thanks.

[good_evil]

Sorry, i missed onething. I had read many articles about serial connection with db9. Can i use RTS (Request to Send) or CTS (Clear to Send) pin to make a handshaking? Or i should use DSR (Data Set Ready) or DTS (Data Terminal Ready) pin? What are differences between Data Set and Data Terminal?
Thanks.

[S_M_A]

Yes, using hardware flow control will most likely work alright if you set up your phone correct.

Since you have problems with data overrun I guess you try to poll the serial interface instead of using interrupts? In my opinion using interrupts is the best way to do it but If you intend to stick to polling, the quickest way to solve the issue is to lowering the baudrate (AT +IPR=xxx on the phone I used a long time ago).

The projects involving serial interfaces which I have been involved in (during the last 15-20 years or so) there has never been a need for hardware flow control so I have to admit I know nothing about it. I guess there is a lot of internet articles about it though so it should be fairly easy to find out the details.