Hi Woody,
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Thanks for your interest in the smart filter controller. As I answered your question via email, I'll include the core of the reply here for others that may have the same question.
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I used a generic Arduino Nano to prototype the circuit. So the chip is a ATMega328p and the pinout it that of the Nano pins.
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The pinout is in the source code, here:
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I should add the schematic to the github repository, however here is a post showing the generic schematic. It may be better to use gates/filp-flops that have some hysteresis to make the circuit more immune to possible clocking on noise around the switching threshold.
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One additional note, I was looking at the ATtiny85 data sheet last night. To my surprise this little chip has a PLL to multiply the clock by 8. It can provide a 64Mhz clock to some of the I/O logic. It might be able to count the approaching 30Mhz frequencies of the HF bands without a pre-scalier (although I'll need to look more carefully at the data sheet to be sure). Now if there is another AVR chip that has the same high speed clock and more pins that would be ideal for this project.
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I took advantage of the sale Microchip is having at the moment on the PICkit 4 programmer/debugger (does both PIC and AVR chips), so I'm no longer limited to the chips supported by the Arduino boards and IDE, so I may look for other processors that can handle higher counter/timer clock frequencies than the ATmega328p used on the Arduino boards.
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The Arduino Nano with the pre-scaler is still the path of least resistance, and a good way to go.
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Tom, wb6b
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