SMS via pic

[kenandere]

Hi friends,

I am trying to prepare a common project for checking and controlling some stuff in my village house; Sensor -> Pic -> Mobile Phone and Mobile Phone -> Pic -> Actuator by using SMS.

But already I spent a considerable time and still I could not succeed. In fact I already checked the forum, but unfortunately still could not succeed.

And as a general information;
Mobile phone is T630 sony ericsson, which supports txt mode.
I use 16F877 (20/P), MAX232, 4 MHz Crystal,
I use pic basic pro,

Below I put some info about my latest situation:

(1) I can communicate between pic to hyper terminal and hyper terminal to pic without problem.
I used a USB1.1 to RS232 converter cable, because I don’t have serial port on my notebook.
Schematic is as shown:

PBP code is as shown:
' Initialization
TRISB=%00000000
PORTB=%00000000

'Definitions
DEFINE OSC 4
DEFINE HSER_TXSTA 20h
DEFINE HSER_RCSTA 90h
DEFINE HSER_BAUD 2400
DEFINE HSER_SPBRG 25

BEGIN:
PORTB = 0
HIGH PORTB.7
PAUSE 1000
LOW PORTB.7
HIGH PORTB.6
HSerout ["AT",13,10] 'TEST COMMUNICATION
HSERIN 5000,begin,[WAIT("OK")]
HIGH PORTB.5
PAUSE 500
GOTO begin

'END
End

Hyper Terminal Settings are as below:
Bits per second:2400 / Data Bits:8 / Parity : None / Stop Bits:1 / Flow Control :None

Both simulation and real test are succeeded;
(2) I can communicate between pc to mobile and mobile to pc without problem. Below you can see some of commands and answers.
Again I used a USB1.1 to RS232 converter cable.

AT
OK
AT+CMGF=?
+CMGF: (0,1)

OK
AT+CMGF=1
OK
AT+CMGS="0XXXXXXXXXX",129 ‘ ”0XXXXXXXXXX” – TEL NO ‘
> "SELAM DENEME MESAJIDIR"
+CMGS: 0

OK

(3) Test Communication between pic and mobile phone,

The same
- pic basic pro program same as above,
- 16f877, 4Mhz, 2400 8-N-1 baud rates.
- the same connections as:
RS232 pins 1-4-6 interconnected, pins 7 and 8 interconnected, pin 5 earth,
RS232 pin2(RX) to leg7(T2OUT) of max232
RS232 pin3(TX) to leg8(R2IN) of max232
PIC RC6/TX to leg10(T2IN) of max232
PIC RC7/RX to leg9(R2OUT) of max232

But this time I can not see the 3rd led, wait 5 seconds and return back to loop. 
This is where I stop, My biggest concerns are :
- baud rate,
- crystal 4Mhz may be not enough,

May I have you kind suggestions?

Most probably one these main problems i have:
- maybe pic can not receive "OK" message from mobile phone
- maybe mobile phone can not receive "AT" command from the pic

[aratti]

RS232 pin2(RX) to leg7(T2OUT) of max232
RS232 pin3(TX) to leg8(R2IN) of max232

Since the phone is a DCE device you must change your connection:

RS232 pin3(TX) to leg7(T2OUT) of max232
RS232 pin2(RX) to leg8(R2IN) of max232

Al.

[kenandere]

Thanks aratti for the information,

Frankly speaking i did not have any idea what is DCE device, so i checked the internet and found that:

Typically, one is called DTE (Data Terminal Equipment) and the
other is called DCE (Data Circuit-Terminating Equipment). For instance, in EIA-
232 communications, DTE devices (terminals, PCs, mini-computers) are quite
stubborn and only want to talk to DCE devices (modems, multiplexers), and vice
versa. For this reason, you may connect a PC COM port to a modem using a
"straight through" EIA-232 cable. However, when you must connect a PC COM
port to another PC COM port, you must use a "null-modem" cable. The function
of the null modem cable is to "trick" the DTE device into believing that it is
talking to a DCE device by cross-wiring the data and control pins in the cable.
Ethernet AUI (Attachment Unit Interface) also uses the DTE/DCE convention,
However, itÕs not as simple as it is with EIA-232.

So in this case i think you meant: Microcontroller and mobile phone are both DCE device, so i need to cross-over RX and TX cables of the serial port.

I will try this asap and inform back the result, thanks a lot.

[kenandere]

Hi again,

in normal connection;
* RC6/TX -> T2IN AND T2OUT -> PIN2 RXD
* RC7/RX -> R2OUT AND R2IN -> PIN3 TXD

i tried also cross-over connection, but no success ;
* RC6/TX -> T2IN AND T2OUT -> PIN3 TXD
* RC7/RX -> R2OUT AND R2IN -> PIN2 RXD

i tried both connections again but still no success

any idea or suggestion is really appreciated , thanks...

[kenandere]

Hi Everybody;

Let me tell you, one of my observation;
i checked the voltage levels at RXD and TXD pins of the mobile phone in both normal and cross-over connections:

in normal connection:

* RC6/TX -> T2IN AND T2OUT -> PIN2 RXD;
PIN2 has negative voltage around 7 or 8 Volts,
When signal comes from pic , it makes a sudden change

* RC7/RX -> R2OUT AND R2IN -> PIN3 TXD
PIN3 has 0 voltage,
When signal comes from pic , it does not make a sudden change


i tried also cross-over connection;

* RC6/TX -> T2IN AND T2OUT -> PIN3 TXD
PIN3 has negative voltage around 6 or 7 Volts,
When signal comes from pic , it makes a sudden change

* RC7/RX -> R2OUT AND R2IN -> PIN2 RXD
PIN2 has negative voltage around 5 or 6 Volts,
When signal comes from pic , it does not make a sudden change

Do you have any idea, what is going on ?

[kenandere]

Hi people, try-outs continue

I started to try different baud rates with different crystals as below:
4Mhz/2400 - 4Mhz/4800 - 8Mhz/4800 - 8Mhz/9600

But during these changes, of course I need to make some different definitions about serial communication:

'Definitions
DEFINE OSC 4			'for 4 Mhz
'DEFINE OSC 8			'for 8 Mhz

DEFINE HSER_TXSTA 20h	'I wonder shall I define as DEFINE HSER_TXSTA 24h???
DEFINE HSER_RCSTA 90h	'same for all

DEFINE HSER_BAUD 2400	'for 2400 Baud rate
'DEFINE HSER_BAUD 4800	'for 4800 Baud rate
'DEFINE HSER_BAUD 9600	'for 9600 Baud rate

DEFINE HSER_SPBRG 25		'for 4Mhz/2400 & 8Mhz/4800 with an error %0.16
'DEFINE HSER_SPBRG 12	'for 4Mhz/4800 & 8Mhz/9600 with an error %0.16

DEFINE HSER_CLROERR 1	'same for all

'Initialization
TRISB=%00000000
PORTB=%00000000

'Program Starts
BEGIN:
PORTB = 0
HIGH PORTB.7
PAUSE 1000
LOW PORTB.7
HIGH PORTB.6
HSEROUT ["AT",13]	'send AT to modem followed by a CR and line feed
HSERIN 5000, BEGIN, [WAIT("OK")]	'now wait for 5secs until OK is received however
HIGH PORTB.5
PAUSE 500
GOTO BEGIN	'if it is not then goto the SMS routine again

'END
End

Unfortunately none of above succeeded