PIC Debugging Osciliscope Speed

[cibressus]

I'm new to PIC Controllers, Digital Logic, and signals in general. But i'm really interested in them.

How fast of a osciliscope do I need to experiment with PIC Controllers?

I have a piece of software that lets me use the line in on my sound card, which is 44khz, is that fast enough?

[fkaCarel]

No 44khz is CD sound. For processor debugging, like a PIC, you need a 2 or 3 channel, 20 or 40 mhz scope. If your PIC is 4,4Mhz (just a nearby convenient number), than 100 clock cycles have gone by in your 44khz time window. So you see nothing.

[sswitaj]

Well, you can't use a sound card, it's not fast enough.

Depending on how fast a circuit you're building, a fairly simple scope should be fine. A good rule of thumb is that you need 3x the bandwidth of the highest signal you need to look at in detail, but for hobbyist applications, you can relax this a good bit.

With analog scopes, the bandwidth spec tells you where the display response starts to roll off, but then it falls off gracefully. With digital scopes, the numbers are a little less meaningful. Name-brand equipment manufacturers (like Tek & HP) rate their digital scopes the same way, they start to roll off at the max frequency, but do so gracefully since the sample rate is actually much higher.

Manufacturers of PC "pod scopes" often rate their scopes by quoting the sample frequency - in the case of a sound card scope, 44KHz. Whole books are written on sample theorum, but 44K samples can show you the presence of a 22KHZ signal, or show you some shape detail in a 10KHZ signal.

Either way, for general PIC work, you'll probably want a scope that displays into the low 10's of MHz.

You can pick up a good, clean 40MHz analog scope on e-bay with probes for $75.

My old 40MHz Hitachi V42 is still my favorite analog scope because it has a nice sharp trace.

On the other hand, one of the great irritations of using analog scopes on microcontroller circuits is that it's difficult to observe low duty cycle events (one shot things)

Digital scopes have a monumental advantage here, but they tend to be much more pricey in useful speeds (a two channel 60MHz B&W scope retails for about $950 new)

External USB-pod scopes that go to a dozen MHz are available from companies like bitscope (bitscope.com) and are sort of a comprimise, but anything with fairly good bandwidth is still somewhat pricey for a hobbyist ($500 or so)

On the other hand, don't forget that like any other tool, it's an investment in saving you time. My 20 year old Hitachi has probably paid for itself 10x, and my new 200MHz digital color tek is probably already at break-even

[pminmo]

What makes you think you have to have a scope to experiment with PIC's? You can gain a lot of knowledge experimenting with out one. Most of the time I use a simple logic probe, rather than get a scope out. Admittedly, there are times when you need a scope, but don't let the lack of one stop you from experimenting.

[smarbaga]

i have sucked 8 bits of data at a rate of 800 khz through the pc's printer port from a 16c84, could probably go faster but that was all i needed at the time.
i used the printer port as a data logger