The problem with that is that the relationship between the 15 bit control register and the generated frequency is exponential not linear so that there is no simple way to adjust each digit seperately On 18 July 2014 22:16, Dwayne Reid wrote: > If you have the space and input pins available, I'd be using a rotary > encoder with push-button. Encoder starts off by adjusting '1s', with > roll-over /roll-under to next digits. Push the encoder button in, > now you are adjusting the '10s' digit. Same roll-over / > 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 > or to flash / blink the digit that you ARE adjusting. Whichever is > the most visually appealing / easiest on the eyes. > > A variation on the above is to have a separate push button to rotate > between the selected digit. The encoder button then becomes the > 'Enter' button. This has the advantage of allowing the digit select > 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 > technique, except that they use buttons for up and down instead of a > rotary encoder. 3 buttons total: up, down, rotate left. Works just > about as well, except that I find using an encoder to be easier to > 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 chi= p" > >and a few TTL chips. The range will be from about 0.1Hz to 68MHz and th= e > >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, no= n > >of them entirely satisfactory, but I would appreciate, in the first > >instance, suggestions which are not influenced by my thinking. > > > -- > 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 > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 __________________________________________ David C Brown 43 Bings Road Whaley Bridge High Peak Phone: 01663 733236 Derbyshire eMail: dcb.home@gmail.com SK23 7ND web: www.bings-knowle.co.uk/dcb --=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 .