MFJ MFJ-1270X User guide

Model MFJ-1270X

INSTRUCTION MANUAL

CAUTION: Read All Instructions Before Operating Equipment

MFJ ENTERPRISES, INC.

300 Industrial Park Road

Starkville, MS 39759 USA

Tel: [phone] Fax: [phone]

VERSION 1A

COPYRIGHT 2010 MFJ ENTERPRISES, INC.

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MFJ-1270X Instruction Manual TNC-X Packet Contoller

DISCLAIMER

Information in this manual is designed for user purposes only and is not

intended to supersede information contained in customer regulations, technical
manuals/documents, positional handbooks, or other official publications. The

copy of this manual provided to the customer will not be updated to reflect

current data.

Customers using this manual should report errors or omissions,
recommendations for improvements, or other comments to MFJ Enterprises,
300 Industrial Park Road, Starkville, MS 39759. Phone: [phone]; FAX:
[phone]. Business hours: M-F 8-4:30 CST.

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MFJ-1270X Instruction Manual TNC-X Packet Contoller

MFJ-1270X TNC-X Packet Contoller

For VHF Packet and APRS

Introduction

Thank you for purchasing the MFJ-1270X TNC-X Packet Controller. The
MFJ-1270X is a new Terminal Node Controller design based on the
Chepponis/Karn KISS protocol. It is implemented using a Microchip PIC
16F628A microcontroller, a CML MX614 Bell 202 modem chip, an 8K
Ramtron FRAM, a MAX232A level converter chip, and an op-amp which
provides active audio filtering for the modem. From the beginning, this
TNC was designed to be small, inexpensive, have low power
consumption, and expandable.

The MFJ-1270X features an on-board USB port. The USB port was
added because the design took into consideration that computers these
days lack the old style RS-232 serial ports. There is also an 8-pin
expansion header that allows the addition of "daughter boards". Power
is provided to the daughter board through the expansion header. In
addition, signals that would otherwise go to or from a host PC can be
intercepted by the daughter board at the TTL level and processed. The
I/O on the expansion header speaks "KISS" so that any daughter board
only has to send and receive data packaged in KISS format to access
the core module. This makes the development of daughter boards fairly
simple and inexpensive. For example, daughter boards are now
available that can turn the MFJ-1270X into either of two types of
digipeaters, or into a stand alone APRS Tracker.

In addition, the expansion header provides access to a second on-board
serial port. The X-Track daughter board, for example, uses this port to
receive data from a GPS receiver. The data is then processed and
formed into packets and an APRS beacon is sent. Even without
daughter boards the MFJ-1270X works as a fully functional stand alone
KISS mode TNC.

The idea behind the expansion options was to provide a platform that
would allow additional functionality to be added to the unit with the
investment of very little design time and very few parts.

Power Requirements

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MFJ-1270X Instruction Manual TNC-X Packet Contoller

IMPORTANT: DO NOT PLUG IN THE 8-15 VDC POWER SUPPLY
AND THE 9-VOLT BATTERY AT THE SAME TIME

The power requirements of the MFJ-1270X are very minimal due to the
low power consumption of the design. Using an 8-15 volt DC power
supply capable of 200-300 mA is well within the consumption
specifications. There is also a 9-volt battery snap provided for a 9-volt
battery. This makes the TNC more portable for campers and
backpackers.

IMPORTANT: DO NOT PLUG IN THE 8-15 VDC POWER SUPPLY
AND THE 9-VOLT BATTERY AT THE SAME TIME

Terminal Speed

The MFJ-1270X supports only 4 terminal speeds. Jumpers JP1 and JP2
determine the speed strictly for the link between the TNC and the
computer. The following settings are allowed:

JP1 JP2 Port Speed (Baud rate)

On On 1200 (Default Speed)
On Off 4800
Off On 9600
Off Off 19200

Note that the terminal speed setting does not affect the speed to transmit
data. The out-going or transmit speed is always 1200 baud. Note also
that if you set this baud rate faster than 1200 baud, it is possible for data
to be fed into the modem faster than it can transmit it over the air. This
may eventually result in the transmit buffer filling up.

Setup If You Are Using USB

If you have elected to use the USB port to provide data communications
to your PC, you should begin by acquiring and installing the drivers for
the PC and operating system that you are using. The driver you need is
a Virtual Com Port (VCP) driver. It will make the TNC appear as an
additional com port on your computer so that you can use any packet
radio software that supports a KISS TNC connected to a standard serial
port.

If you use the USB port, do not supply any power to the TNC
through the power jack.. The USB buss can supply the rather
limited power requirements for the TNC. If you are using the

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MFJ-1270X Instruction Manual TNC-X Packet Contoller

USB option, set the board jumpers as follows:

• JP3 On the left two pins (toward C24).

• JP4 Connect the center pin to the pin that is closest to the

center of the board.

• JP5 Jumper pins 1 and 2 (the end closest to Q1) and pins 3
and 4, unless you are using a daughter board.

Setup If You Are Using the TNC’s Serial Port

If you plan to connect the TNC to a standard computer serial port,
set up the jumpers as follows:

• JP3 On the right two pins (toward U5)

• JP4 Connect the center pin to the pin closest to C22.

• JP5 Jumper pins 1 and 2 (the end closest to Q1) and pins 3

and 4

unless you are using a daughter board.

If you are using the on-board serial port, you must supply power to

the TNC. This can be done in one of two ways. There is a
coaxial power jack on the board that can be used to receive
anything from 8 to 15 volts DC. Alternatively you can connect a
9-volt battery to the location marked BAT.

Aux 232

An auxiliary serial port using a MAX232 level converter. Main
purpose is for GPS input for the X-Track daughter board.

Serial Port

A standard DB 9-pin RS-232C serial port.

USB Port

A standard USB port for computers that lack the old style RS-232

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