Kent A. Reed wrote: > Gentle persons: > > The recent discussion of problems with parallel-port cards and > Pluto/Mesa hardware/software reminded me that the subject of good and > bad parallel-port cards (and their underlying chipsets) is not well > treated in the wiki. > > Maybe I'm just not good enough with the search function, but Jon Elson's > warnings on his Pico Systems controller pages are the only places I find > in the wiki that suggest one should be cautious when purchasing a > plug-in card and it's a fair guess that the information will be > discovered mostly by people interested in Jon's controllers rather than > in plug-in cards. > > First, it is important to point out that these problems affect devices that communicate commands and data over the EPP link (Pico and some Mesa products in particular), and does not relate to using the parallel port for step and direction signals, as used with MANY stepper and step-servo drives. > I, for one, would greatly appreciate a new wiki page (linking directly > from the EMC2 Supported Hardware page, say) that warns about the general > problem and identifies chips/boards known to work and those known not to > work and any workarounds that have been found to work. > > I don't want to volunteer to start such a page since I have zero > experience with these cards but I'll help edit the page if necessary > because I'm now on the hunt for plug-in cards for some new-ish > motherboards that lack a parallel port and I prefer to make new missteps > rather than repeat old ones:-) > One would have to have separate tables for EPP-mode and step-direction mode operation. Also, it makes a big difference in step-direction usage if you are using one of the break-out boards or trying to drive stepper drives directly. Some stepper drives are opto-isolated, and need a LOT of current to turn on the optos. Others are voltage input, and need very little current. So, there is no "one size fits all" qualification for a parallel port board, unfortunately.
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