Cheapest way 2 generate 22Khz clock?

And you might be able to absorb a significant portion of your design into the processor. So, the net cost could be less than zero. mike

You could use a 74HC4060, a couple of resistors and 5 1N4148s along with an off-the-shelf 16MHz resonator. That would make an oscillator and a divide-by-728.

Best regards, Spehro Pefhany

Could somebody let me know the cheapest way to generate a stable, reasonably accurate 22Khz, 5V logic level, clock. I'd prefer to use a

Hi Spehro, Hi Mrk,

Or, if you don't need the divider, use a 74HCU04. This is the unbuffered version of the 74HC04. The 4060 also has an unbuffered oscillator section which is great but with the HCU04 you'll get several uncommitted inverters for other uses.

Regards, Joerg

I don't have a 4060 data sheet here, but I think there is a problem or two with that idea.

The 4060 is a ripple counter. 728 = 512+128+64+16+8 so there are 3 delays from the oscillator to the first bit of the decoder. You may be already a cycle late by time the decode happens.

It seems to me that the reset pin of the 4060 effects to oscillator. As I said I don't have the data book here.

If the OP can stand the error, the 11.0592MHz crystal divided by 512 is

Before anyone else says it "use a PIC"

In that case, you might be able to use the existing PIC to generate the 22 kHz.

Leon

OK so a PIC seems to rear its ugly head once again (there is already one in another part of this design) which one should I use and is there any pre-written code I can use, as my programming skills are in the beginers stage.

This code is the equivalent of a "hello world" program. Just initialize the SFRs, toggle the output, delay and loop to repeat from the toggle. A 16 or 8MHz resonator should give good results. Run it in simulation (MPSIM) with stopwatch to make sure the delay is exactly what it's supposed to be. Learn how to write the delays without using all NOPs (but that would work too).

To do it as part of another program, you'd probably want to use capture-compare hardware (set to automatically toggle an output pin on match) and interrupts, with a high clock frequency if you want any processor bandwidth left at the end of the day- it will require an interrupt every 91 instructions at 16MHz, so keep the ISR short and sweet- save the context, add a constant to the compare register and return/restore the context. You'd probably have the equivalent of a 8 or 10MHz PIC left when this is running, with one less CCP module.

Best regards, Spehro Pefhany

I think that may be too much for my programming skills, so I would like to use a dedicated PIC on its own, any device/firmware suggestions please?

there

to

That may be a problem even for an expert, depending on what is already running on the little bugger.

But any pic will do. Just pick a pic.

In message , Frank Bemelman writes

Hi Frank

The new 6 pin types (PIC10Fxxx) can only run from their internal clock (a great pity for just this type of problem), so if you're planning on using an existing more accurate clock, an 8 pin PIC is the smallest. PIC12F629 would be suitable.

Cheers

"Mark" wrote

Not to belabor the obvious, but would a 555 fit the bill? With a trim-pot, maybe?

'Stable' and 'reasonable' mean different things to different people. Do you have any numbers: %/degree C; %/month; %/year; % unadjusted accuracy ...

Importantly, what is the application for the 22kHz signal? What sort of thing does it go into: oven timer, robot, small rocket, stereo, dog whistle ...

If that were known I think you would get a far more optimum solution from this group.

There is an easy crash-bang solution that requires zero programming skills.

Choose any PIC that will work with a 4MHz 3-legged resonator. A 4MHz PIC will do an instr every 1uS. 21739Hz is a period of 46uS. So have a simple programme loop that is 46 instructions long.

Instruction#01. Set the output pin to a 1. NOP NOP

"Tony Williams" a écrit dans le message de news: snipped-for-privacy@ledelec.demon.co.uk...

LOL. Makes me wonder. Add a couple ADD or INC instrructions and you'll have a NOP DDS (neat oddly programmable DDS).

:)

Don't laugh.... It's an easy quick and dirty way of getting synchronised clocks and/or multiple phases.