User manual

GSM modem protocol for pCO
2
Carel code +030220330 Rel. 2.0 del 30/10/02
22
3. pCO
2
/GSM PROTOCOL SELECTION
The protocol is selected through the system variable SERIAL1_PROTOCOL. The values for this variable and their related
protocols selected on pCO
2
are:
SERIAL1_PROTOCOL SELECTED PROTOCOL MODEM TYPE
2 “Remote supervisor” with
traditional modem not GSM
Analog standard
10 “Remote supervisor + SMS” with
modem GSM
GSM
4. CONNECTIONS
4.1 RS232 serial card
The pCO
2
communicates with the GSM modem using the RS232 standard, and so it is necessary to install the RS232 serial
card, Carel code
PCO200MDM0
in the pCO².
The connection to the modem is made using the 9-pin male connector on the card. The meanings of the pins on the connector
are as follows:
pin meaning pin meaning
1 CD 5 GND (frame)
2 RX 6 n. c.
3 TX 7 RTS
4 DTR 8 & 9 n. c.
Tab. 3.1.1
As for the technical specifications and the installation of the serial card, follow the instructions described on the instruction
sheet enclosed with the card itself.
4.1.1 Setting the baudrate between the pCO² and the modem
The communication rate between the pCO
2
and the GSM modem is set to 9600 baud by default. In any case, this can be
modified using the application program, if the modem allows. One of the main causes of the failure of the modem initialization
procedure from the pCO² is the incorrect setting of the baudrate.
4.1.2 Auto-baudrate problem in the SIEMENS T35
In some firmware revisions of the SIEMENS TC35 modem, in data transmission mode, after the modem sends the
“CONNECT...” string, it can no longer transmit unless the first sequence sent is “AT....”. This problem can be overcome by
disabling the autobaud mode using the AT+IPR=19200 command and saving the settings to the EEPROM using AT&W.
It is clear that in this case, having set the modem baudrate to 19200, the serial communication baudrate on the pCO² must be
set to the same value.
4.2 pCO
2
- modem cable
For the connection between the pCO
2
and the modem, it is necessary to use a standard PC-modem cable, 25 or 9 pin male on the
modem side and 9 pin female on the pCO² side, like the one usually supplied together with the modem itself.