CNC Bridgeport with Heidenhein control

Sharing the EPP port won't work. Because the Pico Systems devices have a register address counter that increments for every data transfer cycle, sharing would get the counter out of sync. Anyway, it sounds pretty wierd to have a printer or scanner on the same port as a CNC control that could cause injury if something went wrong. NOT a good idea.
Also, it is not clear if this driver permits the level of throughput required for fast back and forth transfers. It is doing very short bursts each way and does it at about 600 ns/byte on a PCI parallel port.
Well, of course, we had to do it RIGHT. Latching the count so it could be safely read later by the CPU was obvious. Dealing with zeroing the counter while searching for the home index pulse at the same time the servo loop is running was not so easy, but it handles that, too.
Both rtlinux and RTAI work approximately that way.
Some X-86 systems have been running step pulse generation tasks as fast as every 10 us! So, the task switching doesn't take very long.
Reply to
Jon Elson
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Nor is it something which I would intend to do. I don't know how long it has been since I have used a parallel port to talk to a printer. :-)
O.K. Someone would have to do the experiment, I guess.
It depends on how many registers need to be preserved and re-loaded. The SPARC cpu has a lot more registers than the X86 family of processors -- but it also has multiple sets of registers, so a process switch *can* be fast -- until you get more active processes than you have sets of registers -- then you still need to save everything from a set so it can be reloaded for another process.
A graph of load average vs increasing number of processes is a very shallow graph up to a certain point (which varies with which model of SPARC is involved, as the number of register sets has been increasing through the years) but at a certain number of processes the curve becomes suddenly much steeper.
Enjoy, DoN.
Reply to
DoN. Nichols
Me, either. I'm thinking about cutting the plugs off of at least a 55 gallon drum of parallel printer cables to sell them for scrap copper. Of course there won't be much copper after they are run though a wire crusher to remove the insulation. It would barely fill a two gallon bucket. :(
I have a lot of 15 & 25 foot printer cables, and a lot have gold plating on the connector shells that caught the eye of the gullible who bought them.
Reply to
Michael A. Terrell
There are cheap monochrome security monitors around. They are typically in 9" or 12", but I've seen 21 inch, as well. I have some aluminum cased composite monitors that were used as computer monitors, but I haven't used any in about 15 years.
Reply to
Michael A. Terrell

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