World of Ham Radio 1994 January/AMSOFT_1994.iso/packet/docs/packet13.doc

Text File | 1993-12-31 | 5.8 KB | 99 lines

INTRODUCTION TO PACKET RADIO - Part 13 - by Larry Kenney, WB9LOZ

In this part of the series we'll take a look at many of the TNC commands
available to you that we haven't covered in previous articles.  We will be
discussing the commands used in the TAPR TNC2 and TNC2 clones.  You might
find that some of the commands are not available in your particular TNC or
that they're used in a slightly different manner than the one explained
here.  Please refer to your owner's operating manual for specific details
on how to use these commands in your TNC.

8BITCONV:  This command enables the transmission of 8-bit data in
converse mode.  Used with AWLEN - see below.  For normal packet operation,
such as keyboard to keyboard transmissions, use of bulletin boards, and
transmission of ASCII files, 8BITCONV should be OFF.  If you need to
transmit 8-bit data, set 8BITCONV ON and set AWLEN to 8.  Make sure that
the TNC at the receiving end is also set up this way.  This procedure is
normally used for transmission of executable files or a special non-ASCII
data set.

AWLEN:     This parameter defines the word length used by the serial
input/output port of your TNC.  For normal packet operation, as described
above, AWLEN should be set to 7.  Set to 8 only if you're going to send
8-bit data.

AX25L2V2:  This command determines which level of AX.25 protocol you're
going to use.  If OFF, the TNC will use AX.25 Level 2, Version 1.0.  If ON,
the TNC will use AX.25 Level 2, Version 2.0.  Note: Some early TNCs will
not digipeat Version 2.0 packets.  With AX25L2V2 OFF, if your TNC sends a
packet and the packet doesn't get acknowledged the first time it was sent,
it will send it again and again, until an "ack" is received or the TNC
retries out.  With AX25 ON, if your TNC sends a packet and doesn't receive
an "ack" the first time, it will send a poll frame to see if the other TNC
received the packet.  If yes, then it would continue, if not then it would
send the last packet again.  The advantage here is that short poll frames
are sent, rather than long packets containing data.  This can greatly
reduce channel congestion.  For VHF/UHF operation, it is almost essential
that every TNC have AX25L2V2 ON.  Many operators have suggested that
Version 2.0 NOT be used on the HF bands as it tends to clutter the
frequency with poll frames.  See the CHECK command below for related
information.

BEACON:    Used with EVERY or AFTER to enable beacon transmissions.
   BEACON EVERY n  -  send a beacon at regular intervals specified by n.
   BEACON AFTER n  -  send a beacon once after a time interval specified
                      by n having no packet activity.
n = 0 to 250  -  specifies beacon timing in ten second intervals.
                 1 = 10 seconds, 2 = 20 seconds, 30 = 300 seconds or
                 5 minutes, 180 = 1800 seconds or 30 minutes, etc.
For example, if you set BEACON EVERY 180 (B E 180), the TNC will transmit a
beacon every 30 minutes.  If you set BEACON AFTER 180 (B A 180), the TNC
will transmit a beacon after it hears no activity on the frequency for 30
minutes.  B E 0 will turn the beacon off. The text of the beacon is
specified by BTEXT and can contain up to 120 characters.  The path used for
the beacon transmission is specified by the UNPROTO command.  YOU SHOULD
USE BEACONS INTELLIGENTLY!  Beacons are often a point of controversy in the
packet community because they tend to clutter the frequency if used too
frequently.  You should keep your beacons short and infrequent, and they
should only be used for meaningful data.  Bulletin boards use the beacon
for advising the community of who has mail waiting for them, clubs use
beacons for meeting announcements, beacons are used for weather warnings,
etc.

CHECK n    Sets a timeout value for a packet connection.  Operation
depends on the setting of AX25L2V2.  The value of CHECK (n) determines the
timing.  Value may be 0 to 250.  Check set to 0 disables the command. If a
connection between your station and another exists and the other station
seems to "disappear" due to changing propagation or loss of an intermediate
digipeater, your TNC could remain in the connected state indefinitely.  If
the CHECK command is set to a value other than 0, the TNC will attempt to
recover.  The setting of AX25L2V2 will determine what action is taken. If
AX25L2V2 is ON, the TNC will send a "check packet" to verify the presence
of the other station if no packets have been heard for n * 10 seconds.
(n = 1 = 10 seconds, n = 5 = 50 seconds, n = 30 = 5 minutes, etc.)  If a
response is received, the connection will remain.  If no response is
received, the TNC will begin the disconnect sequence, just as if the
DISCONNECT command had been sent.  If AX25L2V2 is OFF, after no packets are
heard for n * 10 seconds, the TNC will not send a check packet, but will
begin the disconnect sequence.

CMSG       Enables the automatic sending of a connect message whenever a
station connects to your TNC.  If CMSG is ON, the TNC will send the message
contained in CTEXT as the first packet of the connection.  CTEXT can
contain up to 120 characters.  This feature is often used when the station
is on but the operator is not present.  The connect message is used to
advise the other station of that fact, and often says to leave a message in
the TNC buffer.  If CMSG is off, the text message is not transmitted.

KISS       KISS enables the TNC to act as a modem for a host computer,
allowing programs such as TCP/IP, the G8BPQ Packet Switch, various BBS
programs, and other programs using the Serial Link Interface Protocal
(SLIP) to be run.  Before turning KISS on, set the radio baud rate and
terminal baud rate to the desired values.  Set KISS to ON and then issue a
RESTART command.

                                        (continued in part 14)

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