Sunday, 17 October 2021

DIY Frequency Counter

 

I am concerned with my 6502 reliability now that I have increased the clock speed to 1MHz and I want the ability to slow the clock down (again).  I could revert to my arduino Nano clock but this is quite a bit slower.  Instead I decided to use a decade counter so that I can slow the clock by a factor of 10, 100, 1000 etc.  Chips are ridiculously chep and I can easily add one next to the clock on the breadboard.
It occurred to me that I need to measure my clock speed to be sure the counter is having the expected effect.  It would also be very useful to check the nano clock generated frequenct if I am using it.

Ebay shows some cheap kits alongside expensive "professional" equipment.  I only need a rough idea so a kit is perfect.  It comprises TTH (through the hole) components, 5 x seven segment displays for output and a PIC16 microcontroller for measurement.

The only instruction provided is a link to a youtube video.  It turns out to be very helpful.  Kev, the guy who provides it, makes a board whilst talking, it takes about 5 minutes.  It is reassuring and charming that he is quite amateurish.  There are a couple of important points he makes, firstly how to solder the extra capacitor to improve low frequency measurement and secondly a reference / link to operating instructions he has found.

The board is very nice to solder with well-spaced components and generous solder pads.  I built it and it works.  It accurately tested a 20MHz oscillator as having a frequency 20.064 MHz.  Next I measured the clock speed on my W65C02SXB board, which I understood was running at 8MHz.  The measurement was 1.8MHz, looking at the clock chip on the board I noticed that this is correct - so the tester has already proved itself useful.

In conclusion, I am very pleased with this circuit, it is always nice to solder useful things.  I am now ready to face my next 6502 test.








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