R C wrote:

Dana Myers K6JQ wrote in message ws.com...


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

In which case, AX.25 isn't that hard at all to implement,
HDLC is fairly trivial, and the checksum code can be found
pretty readily (I have a Java port of something I sponged out
of an old RFC if you're looking for sample code).

You'll likely need it all for soundmodem recognize your frames, but
you don't need to do full-on connected-mode AX.25, UI datagrams are
likely enough.

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.

Heh. You're tempting to cobble up the DDS code for giggles and
flash it into an atMega16 I have sitting here ;-)

Dana