To operate a modem on the serial port, the following parameters must be set using the command line under . The leading AT in the command is not usually required, but it is included here for better legibility.
- Modem ID command (Request-ID)
- Command to query the modem identifier. The result is output in the modem status. Default: ATI6
- Reset string (Reset)
- Command to perform a hardware reset on the externally connected modem. Default: AT&F
- Initialize string (Initialize)
- Command to initialize the externally connected modem. The device sends this sequence to the external modem after this has had a hardware reset.
Default: ATL0M1X1S0=0
- L0: Loudspeaker quiet
- M1: Loudspeaker on while connecting
- X1: Operation at an extension
- S0=0: Disable auto answering
- Disable modem echo (Echo-off command)
- When the modem echo is enabled, the external modem sends back every character it receives. The modem echo must be disabled in order for the external modem to function properly. Default: ATE0
- AT check cycle time (Cycletime AT poll (s))
- When disconnected, the device checks the presence and correct functioning of the external modem by sending the string "AT" to the modem. If the modem is connected properly and working, it responds with "OK". The cycle time for the "AT-Poll" defines the time interval in seconds between checks. Default: 1
- AT check cycle count (AT poll count)
- If the external modem does not respond to the number of AT polls from the device set here, then the device performs a hardware reset for the external modem. Default: 5
- Number of rings before answering the call (Ring count)
- Default: 1
- Call answering initialization command (Init. answer)
- The device sends the initialization sequence for answering to the external modem before outputting the accept-call command. Default: <Blank>
- Answer command (Answer command)
- Command to accept a call arriving at the external modem. Default: ATA
- Initialize dial command (Init. dial)
- Initialization sequence for dialing to the external modem before outputting the dial command. Default: <Blank>
- Dial command (Dial)
- Command for the external modem to dial a number. The device takes the telephone number from the list of remote stations and appends it to the string specified here. Default: ATDT
- Escape sequence to terminate data phase or to return to command phase (Escape sequence)
- Command sequence to transmit individual commands to the modem in the data phase. Default: +++
- Escape prompt delay (Escape prompt delay (ms))
- After the escape sequence, the device waits for the time set here in milliseconds before issuing the command to hang up. Default: 1000
- Disconnect (Disconnect command)
- Command to disconnect a call via the external modem (hang up). Default: ATH
Setting up a GPRS backup connection
If the connection is to use a GPRS-capable modem at the serial interface, you will need the APN name and the dial-up telephone number. The following init-strings for the configuration apply to T-Mobile and Vodafone:
- T-Mobile
- Init-string: L0X1M1S0=0+CGDCONT=1, “IP”, “internet.t-d1.de”
- Dial-up number: *99#
- Vodafone
- Init-string: L0X1M1S0=0+CGDCONT=1, “IP”, “web.vodafone.de”
- Dial-up number: *99# or *99***1#
Command prompt:
Entering special characters in the CLI
For a GPRS dial-up, the initialization strings require the entry of inverted commas and equal signs. Certain special characters can be correspondingly marked with a leading backslash:
- *
- "
- =
- space
Example: +cgdcont\=1,\”IP\”,\”internet.t-d1.de\”
As an alternative, the entire command sequence can be enclosed within inverted commas. In this case, those inverted commas which are inside the surrounding inverted commas must be preceded by a backslash.
Example: ”+cgdcont=1,\”IP\”,\”internet.t-d1.de\””
