On Sun, Oct 31, 2010 at 12:25:09AM -0700, Kirk Wallace wrote: > According to the documentation: > http://www.linuxcnc.org/docview/html//man/man9/pwmgen.9.html > > it's pulse density, but I would think the duty cycle would be a constant > 50%, which wouldn't work. I haven't tried it, but I have seen it > mentioned on this list a few times. It may have to do with how the > filter is set up. Maybe like a charge pump, you get more pumps per unit > of time as the pulse density goes up.
The problem is that output ripple increases as pulse density decreases. That's why pulse duration modulation is superior here. (The name doesn't matter much, and what EMC2 does matters less, I think. It's easy enough to set up a PWM channel to do it. EMC2 will never know about it. You're just sending it numbers over the parport, AIUI?) > I looked at the EPP material some more and there is a connector pin for > transferring data and one for address. In order to just get something > working on a very basic level, I can forgo the EPP standard and use > EMC2's parport driver: > http://www.linuxcnc.org/docview/html//hal_drivers.html > > to bit bang my own protocol. Maybe a simple 8 bits of data out and a > strobe. Yes, since you are able to tweak both ends of the link, there's no longer any need to be shackled by e.g. EPP's nibble-wide back-channel. The two strobes, one for address, and one for data, might be worth retaining though, especially if you want multiple outputs. (Or use it as a sync event, to signify start of packet, since you'll be sending multi-byte values, I figure? Channel address could then be the first byte, perhaps.) Erik -- The Chinese economy is one third the size of the US, and yet M2 in China now surpasses M2 in the US", said Dr Zhang. ... [It] is set to overtake Europe within months. - John Garnaut (The Age, 21.10.10) ------------------------------------------------------------------------------ Nokia and AT&T present the 2010 Calling All Innovators-North America contest Create new apps & games for the Nokia N8 for consumers in U.S. and Canada $10 million total in prizes - $4M cash, 500 devices, nearly $6M in marketing Develop with Nokia Qt SDK, Web Runtime, or Java and Publish to Ovi Store http://p.sf.net/sfu/nokia-dev2dev _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
