Johan:
It would be very nice if we could agree on a simple serial protocol
that would allow any PC program, be it DOS or Windoze, to take total
control over the DDS (I know that Andy G4JNT has done something
in this direction).
Please, for serial protocol just use what Andy has already done or do the
exact same functions, Integer steps at the limits of the DDS chip.
With Andy's I can set the DDS to any INTEGER count, steps of 1.1 MilliHz
and I can also go around and set the Clock frequency so that the DDS output
can stay the same while the Reference frequency moves (read drifts hi)
around etc.
This is all best done at high level as I see it. The latest QST has
another DDS design with 1 Hz steps that are not quite 1 Hz really, rather
sad to see the impact of thinking that can only cope with 1 Hz increments hi.
The worst result for me would be doing something like 10 milliHz steps,
which again would be not quite 10 milliHz for those with different
Reference oscillator frequencies. The use of a second DDS to make a nice
round integer clock for a DDS would be the best solution but is overly
costly at the moment.
The 16F628 is ideal for the new way to replace the 16F84. The serial UART
is nice to work with. These devices are also now cheaper than the 16F84's,
well at least they are at the moment by a small amount. For my needs here,
I would give up the rotary control and the LCD, just use a serial port to
do it all.
I hope this finds you having fun....I am still stiff as a board so no
climbing around here yet hi.
Larry
VA3LK
PS, one final point, I would implement a trigger input on the PIC as well
so that one can easily make the whole DDS setup coherent to a 1 Second
resource as well. I have that here now on the BPSK and it could be used to
squeeze a bit out of the system.....
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