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Topic: frequency count with high accuracy (Read 5962 times) previous topic - next topic

john12345

No, although I can see the potential...

I guess the main question is if there is an arduino board capable of accuracy and resolution.

CrossRoads

If one 8-bit processor won't cut it, I doubt any 8-bit processor board will.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

MarkT

Doesn't matter if its one bit or 64 bit, the issue is not processor power, its timing accuracy.  Standard
Uno's have no crystal so are ruled out (unless you replace the ceramic resonator by hand).
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

john12345

There is a guy that created a frequency reference with an arduino and gps module. So I don't think it's a timing issue.

The big thing is to alter the circuit to be counting in the needed lower frequency range and to display the digits.

http://www.google.com/url?sa=t&source=web&cd=1&rct=j&q=arduino%20frequency%20reference%20gps&ved=0ahUKEwiow8nwt97MAhUJPiYKHQk0AowQFggxMAA&url=http%3A%2F%2Fwww.knology.net%2F~gmarcus%2FVFO%2FGPS_Sig_Gen_v1_1.pdf&usg=AFQjCNExogliBBykyw1Kmi3X4EXmxBYgvQ

Crossroads: I think I know the answer to this, but I want to make sure...how did you conclude that 8 bits might not be enough and all the comparisons I keep running into don't talk about bits.  Do you have any data as to which board has what bits?

Thanks

dlloyd

On an UNO, I've tested the FreqMeasure Library with a 100kHz clock signal connected to pin 8. This uses the input capture unit and timer/counter 1 to achieve the highest accuracy possible and is unaffected by any variance in MCU cycles due to entering and leaving an interrupt and processing pending interrupts. I got repeatable results representing 160 UNO clock ticks (10┬Ás).

In the link you've provided, it's curious they didn't use the input capture feature as there's a data line connected to pin 8 instead.

Check out the 16-bit Timer/Counter1 and input capture unit starting on page 111 here.

john12345

Thanks dlloyd. That helped me understand the basics on how to chose the right board. I did not know one had to go so deep into the schematics for a project. I thought it was just a plug and play type thing. Learning something new with every post.

Thanks for everyone's help. I will post some more question later after I do some more digging on power supply requirements and displays.

gpsmikey

Don't forget that you will be periodically switching satellites too - the GPS satellites are not geostationary, so you will periodically switch which one is "visible" to your receiver.  Not sure how that will affect your timing.
mikey
-- you can't have too many gadgets or too much disk space !
old engineering saying: 1+1 = 3 for sufficiently large values of 1 or small values of 3

allanhurst

Hi...
        quite agree with the puzzlement of others as to why you'd need that accuracy for audio. Even so.

Standard processor crystals are +/- 30ppm or so, so you'd have to use an external reference - GPS is probably as cheap as any.

   My big doubt is as to whether it will work at all well.  To measure accurately you must have a super clean source, and any audio with a mike and speaker with background noise involved will be full of all sorts of errors -

you'd need 10 to the 13 signal to noise or getting on that way, which is 260dB.

can't be done.

Allan.

larryd

#23
May 18, 2016, 01:44 am Last Edit: May 18, 2016, 01:46 am by LarryD
@raschemmel

Get some alcohol and remove that sale sticker on your scope  8)

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raschemmel

Quote
@raschemmel

Get some alcohol and remove that sale sticker on your scope 
Done 8)

larryd

No technical PMs.
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MrMark

#27
May 18, 2016, 03:57 am Last Edit: May 18, 2016, 03:58 am by MrMark
There is a guy that created a frequency reference with an arduino and gps module. So I don't think it's a timing issue.
He's claiming 3e-8 performance for it.  You said you needed 1e-10 which is almost 2 orders of magnitude better.  People who do that level of performance start with a pretty fancy oscillator.  (e.g. Thunderbolt-E_DS_0807.pdf)  As such, they're a little pricey by hobbyist standards, though not outrageously so.

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