A mechanical encoder generates signals just like a 'real' encoder (e.g A=20 low, B low, A high, B high) except that all 4 signals get generated=20 between 1 detent and the next. The time between A low and B low is hard=20 to control. You want to measure the time from A low to the next A low,=20 and only increment on A going low. One count per detent, even though=20 you COULD count 2 or even 4 per detent. I'm not sure how well that would work scrolling to 40,000,000 by ones,=20 though. If you can place a cursor on the display, you could use the encoder=20 switch to move the cursor through the digits (1s, 10s, 100s, etc) and=20 turn the encoder to set each number. Or you could blink the current digit. Kerry On 7/18/2014 9:25 AM, David C Brown wrote: > 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 encode= rs > 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 1000= s. >> 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 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .