Electronics > Projects, Designs, and Technical Stuff
3 Dollar Precision Frequency Standard
netdudeuk:
The Uno uses a 328 so that's now supported but I expect that you'd need to lose the boot loader and then it wouldn't really be an Arduino any more. However, those chips are about a £1 from China and you could probably use the Arduino to program it.
paulie:
No need to over-write the bootloader. Hex files can be downloaded with avrdude using serial interface just like any Arduino program. In fact one of the fellows here is using a Pro Mini board and he can still use it for loading Arduino programs when not being used as a frequency reference. It is only necessary to tell the compiler a 20mhz clock is used instead of the original 16mhz. This is done by way of a new entry in boards.txt file.
Hardware modifications to that tiny module were the only tricky part and that wasn't too difficult really. Just a little fine soldering work to reroute the clock to the TCXO which was HUGE compared to the original SMD ceramic resonator. The clock accuracy is like a million times more accurate and precise now. He tells me when running a calendar clock ino file it loses less than two seconds a week.
Modifying a Uno should be much easier with it's full size crystal. Too bad Arduino designers didn't think to bring out the B6/B7 pins which would eliminate the need for any modifications at all. One of the few gripes I have with using these boards whether it be Arduino or non-Arduino assembler, BASIC, or C.
Anyway I will dig up the m328 file and post when I get a minute. Putting out some work related fires ATM.
paulie:
Mega328 file uploaded to first post along with implementation details. Dozens of individuals have worked with the Mega8 version but only a couple guys besides myself with the new one so not as well tested. If anybody finds bugs or even if it works OK it would be appreciated to post your experience.
paulie:
Due to personal need for more convenient access to useful frequencies I modified the original program to include several additional "quick skip" entries. Details in first post.
netdudeuk:
Paulie, I've come to build this project today and notice from the first post that I recently bought the same frequency counter as you.
I'm really pleased with it (although did get caught out by the fact that the red and black are the wrong way round on the keyed source connector) but the display is far too bright.
Do you (or anyone else) know which of the three variable pots is used to control the display brightness ?
I'm guessing the one in the diagram but would prefer not to just give it a go.
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