Parallel port logic analyzer

posted Jan 28th 2008 11:34pm by Will O'Brien
filed under: misc hacks

After reading the latest hackit post, [Ben] sent in this older, but simple logic analyzer. The software was written in windows, but the circuit is simple enough, and most hackers I know have more computers than immediate family members. The circuit uses a HC245 octal bus transceiver to feed the 8 data lines on the parallel port. (You can use a variety of chips for this application, most CMOS buffers will probably be fine.)

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In other words, this just connects stuff directly to your parallel port. Should be very easy to make a Linux driver for this. Too bad my printer is parallel… time to upgrade :D

I think it would be nice to add some kind of playback support. Since those pins on the parallel port are bidirectional, it should be simple enough. Time to pull out my soldering iron!

Posted at 12:53 am on Jan 29th, 2008 by atrain

build one of these for your printer:
the hex file works with the 88, 48 and 168 i think. and besides, its well documented

http://www-user.tu-chemnitz.de/~heha/bastelecke/Rund%20um%20den%20PC/USB2LPT/ul-15.htm.en

then you will have a spare lpt port.

Posted at 1:56 am on Jan 29th, 2008 by Emperor

I built one of these a few years ago, including linux software: http://uvasux.googlepages.com/simplelogicanalyser

Posted at 1:58 am on Jan 29th, 2008 by nickjohnson

comment i left on the diylife board:

Nice design. I wonder if you get subtle flickers when updating the PWM values. I’ve found in my designs on the 14bit pics, that I have to update the PWM when my ” 1 byte cycle counter” wraps to zero rather than immediately. You are clocking at a higher clock rate (I use 4-8mhz internal clocks with up to 10 PWM channels), so your design may not be so sensitive.

Recently, i’ve given up on the PIC and it’s goofy architecture and moved to the Cypress PSOC parts. They are really neat with dedicated digital and analog blocks. You can set up up to 16 PWM (actually I use pseudo random bit sequences, which have less flicker) outputs, and the C compiler is really reliable vs the buggy stuff i’ve experienced w/ the pic (though the PSOC compiler generates crap code). The PSOC has it’s own shortcomings, such as a really inefficient CPU, but the digital and analog blocks more than make up for it b/c stuff is done in HW vs SW. PSOC is really fun, esp when u wrap your head around it’s way of doing things.

Posted at 2:20 am on Jan 29th, 2008 by 8Way

ACK! wrong post. i meant it for the pic rgb color changer. Doh!

Posted at 2:21 am on Jan 29th, 2008 by 8Way

This could probably be improved with the addition of an external power source and some high speed opto-couplers,to protect the computer properly.

Posted at 3:40 am on Jan 29th, 2008 by giskard

I used the Fabulous Logic Analyzer for Linux. It uses pretty much the same hardware. This software and hardware combination were in the kits I gave away at Chaos Communication Camp. The software and schematics are available here: http://tfla-01.berlios.de/

Posted at 9:36 am on Jan 29th, 2008 by abend

This works really well.
I used it last year to view signals from an IR receiver to read the commands that a tv remote control sends out.

Posted at 9:37 am on Jan 29th, 2008 by PixelTricks

Cheers, will build one this weekend. Should last me until I can scrounge the cash for a real one. By the way, anyone have an opinion of analyzers in terms of usb vs standalone?

Posted at 1:46 am on Feb 1st, 2008 by penjuin

You might be interested in yet-another-slow-logic analyzer I have created today: http://martin.hinner.info/electronics/piclogix/

The difference between those linked in this article and comments is that mine is standalone, i.e. requires no PC.

Posted at 12:59 pm on Mar 21st, 2009 by Martin Hinner