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Qtopia - GPRS Networking

• Introduction
• How it works
• Troubleshooting
  • Example connect,disconnect scripts
  • Enabling the debugging of AT commands
  • Changing the packet size for poor signal quality

Introduction

Qtopia has the facilities to configure and connect a GRPS connection as required. This document is provided to help resolve problems in establishing a GRPS connection.

How it works

Qtopia uses the dialup network plugin to establishing a connection see : $QPEDIR/src/plugins/networking/dialup/

In the ideal case

1. The user runs the Internet application and configures a GPRS connection
2. The user selects the newly created GPRS connection and it starts dialing
3. GPRS is established and Internet traffic can occur

Troubleshooting

Example connect,disconnect scripts

Scripts can be provided on request and may be customized to suit your device and GPRS provider. For example:

• Connect chat (connect-chat)

        ABORT "NO CARRIER"
        ABORT "NO DIALTONE"
        ABORT BUSY
        # Change the word internet to the name of your providers APN
        "" "AT+CGDCONT=1,\"IP\",\"internet\""
        OK "AT+CGATT=1"
        OK "ATDT*99***1#"
    

• Disconnect Chat (disconnect-chat)

        \d+++\d\c OK 
        ATH0 OK
    

• GPRS Dial (startpppd.sh)

       #!/bin/sh
       #
       # Start a pppd session via GPRS
       #
       # Usage:
       #       startpppd.sh [PPP peer to call]
       # 
  
       # The following notes apply to the pppd options used. See the pppd man page for more details 
       #  ttyS0 : change to the device that modem is connected to
       #  115200 : lower modem speed if required
       #  noipdefault: pppd must not propose any IP address to the peer!
       #  ipcp-accept-local : Accept peers idea of our local address
       #  modem : use modem control lines; change modem to local if required
       #  novj : Disable all compression
       #  record /tmp/ppp-all-text.log : record all traffic to file shown
       
       set -x
       
       if [ -z "$1" ]; then
       
       /usr/sbin/pppd \
           ttyS0 \
           115200 \
           connect 'chat -s -v -f connect-chat' \
           disconnect 'chat -s -v -- -f disconnect-chat' \
           crtscts \
           defaultroute \
           replacedefaultroute \
           noipdefault \
           ipcp-accept-local \
           modem \
           usepeerdns \
           demand \
           connect-delay 5000 \
           idle 120 \
           nodetach \
           lcp-echo-failure 0 \
           lcp-echo-interval 0 \
           novj \
           nobsdcomp \
           novjccomp \
           nopcomp \
           noaccomp \
           debug
       else
       # call the specified peer 
       /usr/sbin/pppd call $1 \
           connect 'chat -s -v -f connect-chat' \
           disconnect 'chat -s -v -- -f disconnect-chat' \
           record /tmp/ppp-all-text.log \
           debug
       fi
    

Enabling the debugging of AT commands

A debug build of Qtopia will cause all AT commands being used to be printed to standard output. If required rebuild Qtopia with debugging enabled via running :

    cd $QPEDIR
    make distclean
    ./configure  -debug <extra options>
    make
    make cleaninstall

Changing the packet size for poor signal quality

By default a packet size of 1500 will be used by pppd for GPRS traffic. In cases of poor signal quality it may be necessary to decrease the "mru" and "mtu" packet size being used by pppd, to for 512. See the pppd man page for details on setting mru and mtu values.

Configuration file elements to check/update

1. check that /etc/ppp/options does not have papcrypt enabled
2. check the password that may be specified : see /etc/ppp/chap-secrets and /etc/ppp/pap-secrets
3. check the contents of $HOME/Applications/Network/modules/DialUpGPRS*.conf
4. check the contents of /etc/ppp/peers/*GPRS*
5. check that DialupImpl::dialString in $QPEDIR/src/plugins/networking/dialup/dialup.cpp suits your modem. For example you may need to use either
   1. AT+CGDCONT=1,\"IP\" ...
   2. AT+CGDCONT=1,\"PPP\" ...
6. update the /etc/ppp/options file to enable debugging and record ALL traffic. eg add

       debug 
       record /tmp/ppp-all-text.log 

7. modify the connect-chat, disconnect-chat and startpppd.sh to suit your modem and internet provider : at least
   • in connect-chat change internet to the name of your providers APN
   • in connect-chat change the GPRS init/dial string as required

Dialing with the example GPRS Dial script

1. Ensure that Qtopia and pppd are not running
2. Start pppd via running startpppd.sh
3. Ping an non-local address : eg

    ping 216.239.39.99 

4. Confirm that pppd attempts to start the link and review the content of /tmp/ppp-all-text.log
5. If needed send the recorded traffic as setup in step 2 in a tar.gz to support