@CHIP-RTOS - PPP Interface

The PPP server must be configured using the  chip.ini file sections [PPPSERVER]
and [SERIAL].   All entries for configuring the PPP server are listed in the config.htm file.

Here is an outline of the steps required to configure the PPP server.

1. Disable/enable PPP server
   ENABLE=0 or ENABLE=1
   By default, PPP server is enabled.
   
   
2. Select a serial port for the PPP server to use with the COMPORTdirective.
   
   Important :
   
   The COM and EXT port of the IPC@CHIP® has only CTS,RTS,RxD and TxD lines,
   so you have to configure your modem with DTR always on.
   (e.g. AT cmd for a ZyXEL modem: AT&D0)
   
   
   
3. Increase the send and receive queue sizes of the chosen serial port (EXT or COM).
   Recommended size is 4096 Bytes.
   
   Example  chip.ini settings for the EXT port:
   
   [SERIAL]
   EXT_RECVQUEUE=4096
   EXT_SENDQUEUE=4096
   
   
4. Select the flow control mode for the PPP server serial port.
   
   
5. Set the baud rate of PPP server's serial port e.g. BAUD =19200   (default is 38400)
   
   
6. Select usage of a modem : MODEM=1.
   The default is 0 (null modem cable).
   
   
7. Define a pio as low-active modem DCD input signal: DCPPIO=1.
   The default is 0 (no pio pin speicifed).
   
   

8. Set the IP Address of the PPP server interface e.g. ADDRESS=192.168.206.4
   
   
9. Set the REMOTE IP Address for the connected peer.
   
   There are three different possibilities for configuring PPP server IP addresses on the IPC@CHIP®:
   
   
   a)   If valid addresses for IP Address and REMOTE IP Address are declared in chip.ini, the PPP server wants to use this configured IP for its own and wants to configure the remote peer with the defined remote address.
   
   b)   If only IP Address is declared in chip.ini and REMOTE IP Address is set to 0.0.0.0, the PPP server wants to use this configured IP address and expects the client to use their own address.
   
   c)   If both entries IP Address and REMOTE IP Address are set to 0.0.0.0, the PPP server expects an IP address from the peer.
   
   
10. Define net mask and router default gateway, e.g.
    NETMASK=255.255.255.0
    GATEWAY=192.168.206.4
    
    Note about IP FORWARDING:
    The TCP/IP stack of the @CHIP-RTOS supports different network interfaces, Ethernet and PPP, so the IPC@CHIP® can forward IP packets between these interfaces.   If you define a gateway in the PPPSERVER section of the chip.ini for the PPP server interface, it becomes the default gateway for all interfaces when a PPP link to the server is established.   During a PPP server connection the command ipcfg indicates this default gateway.   After the PPP session, the old gateway (if any) for the Ethernet interface will be restored.   As of @CHIP-RTOS version 070, the TCP/IP API supports adding and deleting a default gateway:
    
    
    
11. Choose authentication mode with the AUTH directive.
    
    
12. Initialize the modem.
    
    You can define three sets of modem initialization parameters.   These parameters are used to initialize the modem at the start of the IPC@CHIP® @CHIP-RTOS and after a modem hang-up following a PPP session.
    
    Each of the three parameter sets consists of the following four parameters:
    
    • INITCMD string - Command sent to the modem to initialize it.
      
    • INITANSWER string - Expected modem response to initialization command.
      
    • INITTIMEOUT integer - Number of seconds to wait on answer from modem.
      
    • INITRETRIES integer - Number of times to repeat modem initialization sequence if a previous attempt fails.
      
      
    Example:
    
    INITCMD0=ATZ
    INITANSWER0=OK
    INITTIMEOUT0=2
    INITRETRIES0=3
    
    INITCMD1=AT&D0
    INITANSWER1=OK
    INITTIMEOUT1=2
    INITRETRIES1=3
    
    INITCMD2=AT
    INITANSWER2=OK
    INITTIMEOUT2=2
    INITRETRIES2=2
    
    A timeout value 0 means wait forever for the modem's answer.
    
    If you enter the string NULL at an INITANSWER (e.g. INITANSWER0=NULL), the IPC@CHIP® PPP server will not wait for an answer from the modem.
    

    
    

13. Define a maximum of three modem commands for getting connected to the remote peer.
    Example:
    
    CONNECTMSG0=RING
    CONNECTANSWER0=ATA
    CONNECTTIMEOUT0=0
    CONNECTMSG1=CONNECT
    CONNECTTIMEOUT1=60
    
    These are the default values for modem connect commands.
    In this example the PPP server waits forever for the RING message and sends
    an ATA to the modem if it responds to the RING.   After that the server waits
    a maximum of 60 seconds for a response to the CONNECT message.   The modem link
    is established.   The server now establishes the PPP connection to the remote
    client.
    
    Note:
    Do not use the AT command ATS0=1.   This will cause the modem to automatically answer the call without waiting for the PPP server.   This is too fast for the PPP server.

14. Hang-up the connection.
    
    The PPP server will attempt to hang-up the modem when either a connection
    is closed by a remote peer, or if the modem initialization failed during
    the IPC@CHIP® boot process.
    
    
    1. Switch the modem into the command mode (CMDMODE and HANGUPDELAY)
       
       Example:
       
       CMDMODE=+++
       HANGUPDELAY=2
       
       These are the default values.
       
       
    2. Define modem commands and expected answers for hang-up.
       Again, up to three sets of these parameters can be given here.
       
       Example:
       
       HANGUPCMD0=ATH0
       HANGUPANSWER0=OK
       HANGUPTIMEOUT0=2
       HANGUPRETRIES0=1
       
       
       If you enter the string NULL at an HANGUPANSWERx (e.g. HANGUPANSWER0=NULL), the IPC@CHIP® PPP
       server will not wait for an answer from the modem.
       
       

15. Control the online state while PPP session is open.
    
    You can define three sets of modem control parameters.  These parameters are
    used to check the online state of the modem during an opened PPP connection.
    
    
    1. Enable online control sequence MODEMCTRL=1 or MODEMCTRL=2
       
       The default is 0 (disabled).
       Also you have to configure a control time interval (in seconds).   Two different modes are provided:
       
       MODEMCTRL=1:
       After each time interval during which the PPP server receive no data, the server executes the configured modem commands.  
       
       MODEMCTRL=2:
       After each time interval the server executes the configured modem commands.  
       In both cases the server closes the connection, if one of the expected answers timed out. In this mode the configured modem commands are not printed via stdout at execution time, even if MODEMTRACE is enabled.
       
       Example:
       MODEMCTRL=1
       
       
       
    2. Define a CTRLTIME.
       E.g. CTRLTIME=120      default is 60 seconds
       
       Each of the three parameter sets consists of the following four parameters:
       
       • CTRLCMD string - Command sent to the modem to initialize it.
         
       • CTRLANSWER string - Expected modem response to control command.
         
       • CTRLTIMEOUT integer - Number of seconds to wait on answer from modem.
         
       • CTRLRETRIES integer - Number of times to repeat modem control sequence if a previous attempt fails.
         
         
       Example and default settings:
       
       CTRLCMD0=+++
       CTRLANSWER0=OK
       CTRLTIMEOUT0=3
       CTRLRETRIES0=1
       
       CTRLCMD1=AT0
       CTRLANSWER1=NULL
       CTRLTIMEOUT1=1
       CTRLRETRIES1=0
       
       If you enter the string NULL at an CTRLANSWERx (e.g. CTRLANSWER0=NULL), the IPC@CHIP® PPP server will not wait for an answer from the modem.
       
       
       
    
    
16. Define a time out value in seconds after which the PPP server hangs up
    the connection if no data comes in from client during this timeout period.
    
    E.g. IDLETIME=160      default is 120
    
    

IPv6 configuration of the PPP Server