Some background... I started hacking PC's after I got my first TRS-80 Model I. The RS manual actually came with a description of how to use the cassette on/off switch to turn a coffee pot on and off automatically!
Later I moved to X-10 technology, but that's another story.
I used the Centronics (SPP) printer port to build a sonar unit with little more than assembly code, a microphone and speaker. I then hacked the mouse and game ports for more digital and analog input fun and then the keyboard and finally the serial port. I still have the remnants of various wedges and video capture devices, etc. that used the various ports.
I bought a 12 bit A/D converter and used it for all sorts of bench top stuff and finally retired it to a role doing home security by monitoring and recording the outputs from various IR, pressure, temperature and other sensors and switches.
When Windows XP came along with its greatly improved motion detection capability the A/D converter was again available for a digital input so...
The reason I decided to use a printer port was because it was the easiest of all the methods I had used before - until XP that is.
I'm not sure about the software that comes with the USB to Parallel converters that run as little as $10, but if they support reading and writing of
raw digital data to and from the port then they can be used as well.
Essentially all this circuit does is to use 10K pull up resistors to keep the Hall Effect sensor output and the Centronics line level input from floating when not active so you get true binary input and nothing else. You can also substitute any
10ma LED and resistor combo to replace a volt meter to read the sensor output by lighting up an LED for manual input into a PC. Be sure to limit the current required to sink the LED's to 10ma unless you add a transistor since this is the current limit the Hall Effect sensors can sink.
Centronics lines 10, 12 and 13 (Acknowledge, Paper Out and Select) are used for input with blue, green, yellow respectively.
If you have an old PC running anything prior to XP then you can use Qbasic or Visual Basic to read port 889. For XP it is virtually impossible (although I did find a proprietary method and I am developing one hinted at by Microsoft tech).
From there its just a matter of doing with the data whatever you want to do. The only thing my software does that might be special is the logical equation it produces from the results and the interpretation of what the equation means for verbose output of any shorts, opens, intermittents, bad mags, etc. that the analysis discovers. One other thing is the graphic which tells exactly when and where a problem occurs.
I will post a circuit diagram here shortly and I have 30 Centronics printer cables on order in case you don't have one of your own. (These things cost $44 each in 1978 but only a dollar or two now.)
And yes, Mike, my primary and intended use for this circuit is now to test whatever outgoing bikes I sell, but was originally intended to help pinpoint a sensor or wiring problem prior to taking a motor apart as the result of various conditions I am subjecting the motor to, although interestingly enough it appears that 10 minutes after testing or 10 seconds after hitting a bump or pothole a previously undiscovered problem can appear.
Anyone know if the USB to Centronics converter cable allows raw digital data to be transfered to and from the printer and if the software that comes with it handles the conversion?
