[aprssig] APRS-B? (FSK data?)

Robert Bruninga bruninga at usna.edu
Mon Jun 24 13:21:39 CDT 2013

The thing I still need clarified about this RF chip:

1) sure, it needs SPI serial data handshaking and control to setup the
chip and all the parameters, but I am still confused about the FSK/DATA

2) After all the configuration is set by the external CPU or PIC chip and
configured for FIFO OFF, then does this single  FSK/DATA pin act like a
simple SERIAL DATA TX/RX line?  (meaning it could be directly connected to
the serial RXD and TXD l ines of a TNC and it would ack llike a serial
connection) or does the data still have to be clocked into and out of the
8 bit buffer using the SPI handshaking for every byte?

I was assuming the external controls via SPI were only for set up and
control, but that the FSK/DATA pin then became a transparent wireless link
to the other end of the link?

I have tried downloading spec sheets but all the links are dead or blocked
for me...


-----Original Message-----
From: aprssig-bounces at tapr.org [mailto:aprssig-bounces at tapr.org] On Behalf
Of Scott Miller
Sent: Monday, June 24, 2013 1:06 PM
To: TAPR APRS Mailing List
Subject: Re: [aprssig] APRS-B?

> Obviously this would not be too difficult for a PC or microcontroller
> to do, but it does increase the hardware and software complexity
> external to the device sharply.
> I.e. are you going to use an entire second computer (Raspberry Pi,
> Arduino, Basic Stamp, etc) to glue a PC to a $20 gadget?

That part's already done:


I had these up and running a year ago, but have been too busy with other
projects to do much with them.  These examples use the OpenTracker USB,
but could just as easily have a Tracker3 processor.

When I went to test them last year, I had a software glitch that was
causing the PA to not power up properly.  I didn't get much range out of
them.  Next week, I'm headed back out to the Black Rock Desert again and I
suppose I could dust them off and give it another try.  Nothing like
60 miles of absolutely flat lake bed out in the middle of nowhere for
testing RF stuff.

Some things need to be nailed down before we have an APRS-B standard.
These units are presently set up to use KISS-style framing and
Hamming(7,4) coding for error correction.  That was for simplicity, not
because it's necessarily the best way to do it.

The rest of the code is pretty much unchanged.  KISS works as usual, along
with digipeating and everything else.

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