Good 74HC parts to have

[GARTHWILSON]

qwertykeyboard wrote:

I don't own an oscilloscope, so would it be useful to buy a cheap little logic analyzer like this: https://www.ebay.ca/itm/USB-Logic-Analy ... SwLSBc-btw
to do debugging and that type of stuff.

It's extremely limited; but at that price, if it doesn't work out, you haven't lost much, except maybe time.

[BigDumbDinosaur]

qwertykeyboard wrote:

I don't own an oscilloscope, so would it be useful to buy a cheap little logic analyzer like this: https://www.ebay.ca/itm/USB-Logic-Analy ... SwLSBc-btw
to do debugging and that type of stuff.

What Garth said. I think it would be a waste of money, but at least it won't be a lot of money. Unfortunately, a good quality logic analyzer is a not-inexpensive piece of gear.

If your system is not too complicated you can debug it with a logic probe, which is a standalone device that is usually less cumbersome to use than a logic analyzer. I have a logic analyzer (and not a cheap one) but I use it much less than I do my two logic probes. Over the years, I have solved many system problems with nothing more than a logic probe and a multimeter.

Acquiring a scope is a worthwhile goal. While a logic probe or logic analyzer can tell you about signal state (low, high or transitioning between states), it can't tell you anything about signal quality. When a circuit gets stubborn, being able to look a signal quality can be very helpful.

[cjs]

qwertykeyboard wrote:

I don't own an oscilloscope, so would it be useful to buy a cheap little logic analyzer...to do debugging and that type of stuff.

For $12 I don't see how it can hurt! In fact, I have one of these sitting in my toolbox, though I've never actually used it.

One thing it's very important to keep in mind with logic analyzers and similar equipment is that they convert analogue signals digital before you ever see them, so if there's a problem in the analogue domain that affects digital signals, you're not going to see it directly. For example, if a signal level is dodgy such that what's supposed to be a 1 is sometimes misinterpreted as a 0, or a clock waveform is dirty, you'll never see that. And if the thresholds at which the LA distinguishes 1 and 0 are different from those of the actual hardware reading the signal, your LA will show different data from what the part under test is actually seeing.

Worry about levels was actually one of the reasons I built this logic probe the way I did: it shows "definitely on," "definitely off" and "neither" and lets me exactly adjust the levels for each state.

[BigDumbDinosaur]

cjs wrote:

One thing it's very important to keep in mind with logic analyzers and similar equipment is that they convert analogue signals digital before you ever see them, so if there's a problem in the analogue domain that affects digital signals, you're not going to see it directly.

That's what I said above:

Quote:

While a logic probe or logic analyzer can tell you about signal state (low, high or transitioning between states), it can't tell you anything about signal quality.