On 09/14/2010 11:49 PM, Hal Murray wrote:
Maybe a PIC to do the modulations trains and a serial interface to set it
up. In all about 3-4 chips. Should not be too hard.
Why do you need more than one chip?
Why can't the PIC generate the 60 KHz signal by bit banging a couple of pins?
I'm thinking of a 2 or 3 bit D/A with 2 or 3 more pins for the low power
portion of the signal.
1 bit might be enough with a good external filter.
It may not be the simplest solution to be the minimal chip-count
solution. By all means, knock yourself out. My intention was for a
simple solution where each part would be simple and clear. If you
bit-bang the hell out of a PIC it will be more tedious but you can get
the result.
I'm proud owner of two TADD-2 PIC-dividers... so I am not against the idea.
You can always write software that beeps 12 kHz out of a 48 kHz
soundboard (4-sample carrier wave) and then use a transistor as a
distortion stage (2N3904?) filter away junk (optional) and use the 5th
overtone distortion for carrier. Maybe a diode (1N914 or 1N4148) may
work just as well.
The tone-lengths is 200 ms, 500 ms and 800 ms so looping the sample
stretches should be trivial, as you have 12 waveforms per ms and need to
modulate 200 ms and 300 ms stretches of the two amplitude-levels to form
the second pulses.
I am tempted to try it out with the laptop or builtin audio of a
crapiola PC. Should not be too hard. Far simpler than bit-banging a PIC.
Cheers,
Magnus
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