If you have the space and input pins available, I'd be using a rotary=20 encoder with push-button. Encoder starts off by adjusting '1s', with=20 roll-over /roll-under to next digits. Push the encoder button in,=20 now you are adjusting the '10s' digit. Same roll-over /=20 roll-under. Push button in again - now you are adjusting '100s'. And so on. I find it best to dim slightly the digits that you are NOT adjusting=20 or to flash / blink the digit that you ARE adjusting. Whichever is=20 the most visually appealing / easiest on the eyes. A variation on the above is to have a separate push button to rotate=20 between the selected digit. The encoder button then becomes the=20 'Enter' button. This has the advantage of allowing the digit select=20 button to be labelled as such. The same process can be used to set output level. FWIW - some of the PID temperature controllers use the above=20 technique, except that they use buttons for up and down instead of a=20 rotary encoder. 3 buttons total: up, down, rotate left. Works just=20 about as well, except that I find using an encoder to be easier to=20 use if I'm trying to "sneak up" on a value. dwayne At 06:17 AM 7/18/2014, 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 Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax www.trinity-electronics.com Custom Electronics Design and Manufacturing --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .