Is it possible to provide PWM output to a speed controller ( such as the Devantech MD03 ) using a PC parallel port ? If possible, I would think there would need to be a background process running to keep telling some controller on the motherboard to output the PWM.)
You can do it with some circuitry, for instance, I am using a Velleman K8000 I/O board. I wire the D/A converter output of the I/O board into a comparator. The other input of the comparator is the ourput of a ramp generator. This produces a PWM signal.
Typically, though, you wouldn't want to drive the PWM directly from the parallel port because you will spend a lot of time in I/O and the frequency will be pretty low.
That tells me exactly what I wanted to know. I didn't really think it would be worth the effort since my thoughts on doing this were to simply reduce the number of extra components / controllers for a PC / mini-ITX based robot.
Cool! I've been using this guy's TRIPOD code and didn't even know he had a working boondog.com site because everytime I looked for it I got a blank page. Thanks !
P.S. This thread is almost gone on my newsgroup server.
About 10 years ago I wrote some experimental code to do servo control all in software on a PC without any buffer circuitry needed. It is very crude and may need some tuning to get the pulses the correct spacing, but it moved a servo to different positions using the UP/DOWN keys....
I now use a Mini SSC RS232 controller
formatting link
make my servo signals (with a USB to RS232 converter).
-howy
this was compiled using borland C.
/////// start of SEROV1.CPP ////// #include #include #include #include
About 10 years ago I wrote some experimental code to do it all in software on a PC without any buffer circuitry needed. It is very crude and needs tuning to get the pulses the correct spacing, but it moved a servo to different positions using the UP/DOWN keys....
-howy
this was compiled using borland C.
/////// start of SEROV1.CPP ////// #include #include #include #include
This will not work with todays PCs anymore because WIndows messes up your timing in the 'for' loop. Actually, a good compiler will remove the 'fro' loop entirely when optimizing. And last but not least, there is no outportb command on WIn2k/XP anymore. The parallelport can only be talked to via drivers.
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