Hi Charles,

Having had a much closer look I can see how you have used CASE to determine the BIT resolution across the four fixed frequencies, and the use to be able to vary the duty cycle across as much of the range as possible.

it should be fairly easy to adapt this to operate on an PIC (possibly with an LCD) and six buttons(or less) . It is handy, and I am glad you posted it.
I am at the moment working on varying frequencies with fixed duty cycle dependant on resolution, but I do note your use of CASE. The IF...GOSUB can be very compile hungry.

Thankyou for your help

Duncan