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Clock Edge Detection in Excel (drdobbs.com)
11 points by gk1 on Oct 2, 2014 | hide | past | favorite | 6 comments



I've always said that anyone working on an electronic system really needs an oscilloscope. Without it, you are effectively blind and just guessing at what the signals on a PC board or on a wire look like. When I first started (a long time ago), those images were mostly transient.

Really? All the scopes I've ever used have had capture modes (although I have never used truly antique scopes). While I forget what the function is called, the scope would trigger on an edge, capture the waveform and freeze it on the screen. Now, this only ever fits a handful of bits (maybe 3-5 ASCII letters) onscreen, but it was really helpful for me. If you wanted to capture data in the middle of a long stream, you could use a second probe for the trigger, and in your code fire a single edge on a secondary pin right as you send the data you want to capture... lot of cool things you could do. Even the old analog scopes are amazingly powerful. I highly encourage anyone doing much scoping to do their best to master it.

But anyway, back to the subject at hand, I just thought I ought to point out to those who are getting into this sort of thing that Logic Analyzers exist for exactly this purpose.


Capture functionality was very expensive, and thus uncommon, until about 15 years ago. It was around that time that Tektronix came out with their low-end TDS200 model scopes starting at around $1,200. That was an amazingly low price at the time.

My analog Tek 442 is probably about 25 years old and still going strong. I hardly consider it antique.


Ah, excellent context. Most of the old scopes I used were at my University, which probably gave me warped perspective, as they were always able to afford the good equipment.


One wonders why the author bothered to make cell formulas in Excel for 500k rows when he used awk afterwards to process all the rows anyway. Spreadsheets are convenient tools, but his formulas seem to be fully awkable? He used two values from the previous row but that is only two variables more.


OK, well, clever, but these days it's easier to buy the right tool for the job or use some thing like a simple FPGA demo board. Even the simplest Xilinx Spartan on a cheap eval board can be programmed quickly to decode just about anything and provide you with real time live data for debugging something like a serial interface. The approach he presents is laborious and far from real time.


Analog scopes could not freeze anything on the screen, unless you had one of the expensive Tektronix scopes with a storage CRT. Most modern scopes that look like analog scopes are really computers front-ended by A/D converters.




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