How to make an oscilloscope out of the YBox2

[johnnyhellfire]

Hi. I just got a YBox2 as a gift from my girlfriend. I've been pondering for the past two weeks what to do with this thing. Til it hit me, an oscilloscope. Nothing fancy, all you need is a power cord, a tv, and the probes. The ideal off having fancy bells and whistles like a battery pack and on borad LCD screen is nice but wanna start with what is already there. this really just needing a widgit with a graphical interface that can be out put on a tv and the probe hook ups. So any help would be nice and to top it off Im new to this whole game so baby steps please LOL

[darco]

What you would want to do is populate those empty spots next to the propeller chip with some headers so that you can make a snap-in "shield" oscilloscope board.

The "easy" way (well, easy as far as hardware goes) way to do A/D conversion with a propeller is to make a Sigma-Delta ADC converter. Unfortunately, you won't be able to make one that works very well due to the distance from the pins. This means that you will need to add a discrete A/D converter IC—which will probably get you better resolution than a sigma-delta converter ever would anyway (depending of course on the quality of your ADC).

As for what would be a good ADC IC, I'm not sure off the top of my head. You want a sample-and-hold converter with something like an SPI interface. If you can find a dual-channel (or more...) version, then even better.

You'll want some sort of buffer in front of the A/D converter to protect it, at least a simple op-amp follower. Be careful which component you choose for this because it will significantly affect the scope bandwidth.

There are LOTS of details that go into making a good o-scope, but I'd aim first to make a snap-in board that works at low frequencies and then later look into making something with better performance.