Dana Myers K6JQ wrote in message ws.com...
R C wrote:
I'm working on a telemetry board and wish to include software FSK1200
(MX-614's are getting harder to find). The official Bell 202 spec is
out of print and hard to find as well, so I pieced this together from
what I can find. Multimon won't decode the output, so I'm likely doing
something wrong. This is supposed to be (once it works) my reference
implementation before I port it to my telemetry board, so I'm trying
to keep it as simple as possible.

Any help or suggestions would be appreciated.

First - is multimon expecting a properly formatted AX.25 frame?
(This code is clearly not creating an HDLC-encoded, AX.25-formatted
frame). It looks like you're sending conventional async-encoded
ASCII. You need to:

That would explain it. I hadn't planned on using AX-25 (TX is the
audio subcarrier of an FM ATV camera; no point in packetizing it since
no digipeaters would be able to hear it, and unit should never be out
of reception range in any case). I had planned on adding framing,
checksums and possibly FEC later.

I was also trying to keep it as simple as possible initially; encode
raw octets and make sure I can decode them.

It may be worth adding the HDLC/ax.25; initial basestation will likely
be a laptop running soundmodem.

Also - I'd avoid the use of transcendental functions (sin()) in the
synthesizer loop ; I'd create a lookup table and index it via an
integer phase accumulator. Off the top of my head, I'd guess a
16-bit phase accumulator and a 256-element sine array would be
plenty. You'd need to precalculate the phase increments for
1200 and 2200 Hz, likely as constants.

That is step 2 The target CPU will most likely be a Mega8535 AVR,
so conversion to integer is definately indicated.

Thanks,
R C
KG4MVB