There has been much contemplation/hacking by other Arduino fans regarding making a "soft" or low-frequency signal oscilliscope and/or digital signal analyser.
A number of attempts have been made, which I'll try to all link here,
Firstly, Here's my "fixed" version of "MacduinoScope":
Buzzs_MacduinoScope.zip
changes to the original:
* I took the macduinoscope code from gabebear's site ( below), and fixed the X-Code project so it's not totally borked.
His OSX application was so confused because 1/2 the project is called "arduinoscope" and 1/2 is called "macduinoscope". I'm suprised it even builds, but it's still got potential!
* see MacduinoScope/build/Release/MacduinoScope.app for the OSX oscilloscope application.
* see MacduinoScope/macduinoscope/macduinoscope.pde for the Arduino Sketch to load into your arduino.
good luck!
History:
arduinoscope logic analyser:
code.google.com/p/arduinoscope/
my comment: binaries assume the first serial port in your system is the arduino, and then borks if it's not. building from processing sources is the only way.
discussions:
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1217011894
poor mans oscilloscope:
http://accrochages.drone.ws/en/node/90
my comment: very slow, requires "processing".
and a linux-only one:
discussion: http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1256923269
code: http://github.com/alvieboy/arduino-oscope/
my comment: have not tried this.
the original "macduinoscope".
it's original author's ( gabebear) website went AWOL for a while, and it's got no really pretty site, but it's original site was/is here:
my comment: this one is FAST! it's using 1-2 Mb/s data streaming off the arduino, totally maxing out the USB link. great! way more than a classic 9600 or 115200 serial link could do.