Post by thread:[EE]: Could PC Parallel port drive a device that n

Hi All, I have a equipment whose operation invloves being triggered by a continuous pulse train of 1 Hz at TTL level. Currently I'm using a funtion generator with TTL o/p for doing that, but I want the operation be more automatic, so I'm considering using the parallel port of a PC to replace the function generator. However I wonder if the parallel port of a PC is TTL compatible. Could anyone give some comments? Thanks in advance! John

On Wed, 2005-10-19 at 11:45 -0700, John Waters wrote: > Hi All, > > I have a equipment whose operation invloves being triggered by a continuous > pulse train of 1 Hz at TTL level. Currently I'm using a funtion generator > with TTL o/p for doing that, but I want the operation be more automatic, so > I'm considering using the parallel port of a PC to replace the function > generator. However I wonder if the parallel port of a PC is TTL compatible. > Could anyone give some comments? Most are TTL compatible. Some will only be 3.3V (i.e. laptops), which might still work fine with TTL hardware, but I wouldn't count on that. A bigger problem is how accurate do you need that 1Hz to be. If you're running just DOS you can get it pretty close, but in Windows expect that 1Hz to glitch every once in a while. TTYL ----------------------------- Herbert's PIC Stuff: http://repatch.dyndns.org:8383/pic_stuff/

{Quote hidden}>-----Original Message----- >From: spam_OUTpiclist-bouncesTakeThisOuTmit.edu [.....piclist-bouncesKILLspam@spam@mit.edu] >Sent: 19 October 2005 20:42 >To: Microcontroller discussion list - Public. >Subject: Re: [EE]: Could PC Parallel port drive a device that >needs TTLtriggers? > > >On Wed, 2005-10-19 at 11:45 -0700, John Waters wrote: >> Hi All, >> >> I have a equipment whose operation invloves being triggered by a >> continuous >> pulse train of 1 Hz at TTL level. Currently I'm using a >funtion generator >> with TTL o/p for doing that, but I want the operation be >more automatic, so >> I'm considering using the parallel port of a PC to replace >the function >> generator. However I wonder if the parallel port of a PC is >TTL compatible. >> Could anyone give some comments? > >Most are TTL compatible. Some will only be 3.3V (i.e. >laptops), which might still work fine with TTL hardware, but I >wouldn't count on that. > Not just laptops either, many modern desktop machines have 3.3volt logic levels on the parallel port. >A bigger problem is how accurate do you need that 1Hz to be. >If you're running just DOS you can get it pretty close, but in >Windows expect that 1Hz to glitch every once in a while. Indeed. A 555 timer is likely to offer far better short term stability and costs pennies. A 32.768kHz watch crystal and binary divider costs litrle more, and gives you excellent accuracy and stability. Regards Mike ======================================================================= This e-mail is intended for the person it is addressed to only. The information contained in it may be confidential and/or protected by law. If you are not the intended recipient of this message, you must not make any use of this information, or copy or show it to any person. Please contact us immediately to tell us that you have received this e-mail, and return the original to us. Any use, forwarding, printing or copying of this message is strictly prohibited. No part of this message can be considered a request for goods or services. =======================================================================

This looks like a job for "Simple Pic". Just program one to put out the signal and be controlled by the parallel port of the pc. Even simpler, use something from the other device or even have it to supply power to the pic to start the oscillator, or in conjunction with the parallel port. Instead of the parallel port, the serial port could be used to turn pic on and off. use the timing of the pulse width when sending a hex 80 and a hex FF to signal the pic to start /stop oscillator. Wouldn't need a fancy RS232 interface on pic, just look at the data pulse and measure time for control. Bill {Original Message removed}