Depending on physical space and how you want the front panel, how about=20
simply using, mechanical encoder pots, using one for each range ?

Units,
Tens,
Hundreds, etc...

and or a high / low switch setting arrangement ?

Peter


On 18/07/2014 11:17 PM, David C Brown wrote:
> I am building a simple pulse generator using an LTC6903 "synthesiser chip=
"
> and a few TTL chips.  The range will be from about 0.1Hz to 68MHz and the
> frequency is set, geometrically, by a 15 bit control word.  I  will be
> using a PIC16F87 to control the synthesiser and drive a display.
>
> My problem is how to set the frequency by hand  using the minimum panel
> hardware.   I need control at the finest level, stepping the control
> register by one but also need to be able to make large frequency shifts
> quickly, perhaps stepping the register by 2^10
>
> I have studied this for some time and come up with several solutions, non
> of them entirely satisfactory, but I would appreciate, in the first
> instance, suggestions which are not influenced by my thinking.

--=20
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