reasons to use a
Earlier project using MX614 was very successful
and many radio amateurs built RM1 USB/RS232 Modem
is a low
modem chip. Excellent chip for a simple low current 1200baud Modem/TNC.
However, keeping in view the high cost of this chip ($9+Postage!!) and recent
unavailability with most suppliers, gives us a good cause to think of
alternatives. Result was this PIC based modem/TNC to get similar
In fact, this project achieved more than MX614 by way of having
capability to store user data and APRS frames.
FoxDigi has following point of interest:
1. A Simple 1200 Baud TNC
2. A stand-Alone APRS
3. An APRS Tracker with GPS Support
4. Works on APRS, with or without a GPS.
However, In this project, I paid special
attention to get an economical APRS Digi, that too without using a
GPS. To achieve this, only a command statement of Location
(Lat/Long.) is required to be included in BTEXT.
FoxDigi has two D9 connectors for outside communications. J1, a D9M is
provided for your transceiver. J2, a D9F is for connection to your
FoxDigi is required to suppy +12V (+7-12V) from Transceiver
connector J1. An internal regulator (78L05) provides +5V for digital
circuits. Current consumption is well below 20ma (Depending on LEDs)
which is good enough for most remote solar powered locations.
FoxDigi uses a standard RS232 driver to interface
with your PC (or GPS) J2 is configured as DCE using D9F connector. A
null modem will be required for GPS. However, it should be noted that
this project is not designed for use like a tracker but rather
a Stand alone APRS Digipeater.
on 8cm X 6cm Double
you will never have to worry about MX614 for your projects.
At moment, two firmware are available: 9600
& 4800 baud. This is only important if you wish to use a GPS
with FoxDigi. Firmware Baud Rate will effect both, the GPS & the
"Hyperterminal" used for config of your FoxDigi.
In a stand-alone Digipeater application, a BTEXT
beacon with your position should be good enough. As the current
consumption of a GPS is perhaps too large to handle at a remote site.