|
A Simple PIC88 based APRS TNC:
Rev0711
In this project, special
attention is paid to get an economical APRS TNC with minimum
current consumption and simple task:
1. A stand alone TNC to replace
MX614 Modem chip
2. Send & Received APRS data to COM
port.
3. Supports "Converse
Mode" and Packet/APRS with Version 1.09 firmware by Dennis/N5VRP
Mini-TNC is a PIC88 based TNC which decode aprs
packets & route to COM port. Mini-TNC has two D9 connectors for outside communications. J1, a
D9F is
provided for your transceiver. J1, another D9F is for connection to your
PC using a simple serial cable to output your received data to your
PC for further processing.
Mini-TNC may be powered by either +5V from USB
(J3) or from D9 Radio connector with +8 to 12V
DC. In this case, 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.
Mini-TNC uses a standard RS232 driver to interface
with your PC. You will require a serial cable to configure internal
parameters of the PIC88
Project
is
designed
on 10cm X 6cm Double
Sided PTH
board and
results
were very
encouraging. A free metal case is avail;ble with kits or
assembled.
PIC firmware for Mini-TNC is available at 4800
& 9600baud and its at V1.09 provided by Dennis/N5VRP. Please
refer N5VRP Document for more details on new firmware compatibility
with your PC.
It should be
noted that since no input audio preset is onboard, audio level
supplied to this tnc may require careful adjustment of received
audio from radio.
However, a modification to previous design is
made keeping in mind varied audio levels. In this design (Rev0711) you
may feed receiver audio direct to PIN17 of PIC88 or route thru MPC6023
active filter.
|
1200baud Mini-TNC (Rev0711) for APRS
