Nice idea, Kerry, and one I hadn't thought of. But what algorithm do you use for slowing it down? I did try measuring time but the cheap encoders don't seem to have very well controlled distance between steps. On 18 July 2014 15:51, Kerry wrote: > One way I have thought about (but have not tried yet) is to use a > mechanical encoder. > Step by 1s. If you see 10 steps in the same direction, start stepping > by 10s. > If you see 10 steps of 10 in the same direction, start stepping by 100s. > If you see 10 steps of 100 in the same direction, start stepping by 1000s= .. > If you see a step in the opposite direction, go back to stepping by 1s. > I don't know if this would be more of a PITA than it's worth. > An alternative would be to measure the time between encoder pulses, and > take bigger steps for quicker pulses. > > Kerry > > > On 7/18/2014 8:17 AM, 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 t= he > > 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, n= on > > of them entirely satisfactory, but I would appreciate, in the first > > instance, suggestions which are not influenced by my thinking. > > -- > 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 .