Jarl Stefansson wrote: >I would like to point out that ARM processors aren't the only way to go >embedded, there are very decent x86 embedded systems available with AMD >(Geode LX/NX) and VIA (CN/CX/C7/Eden) CPUs. > > If you're thinking of the small-footprint PC-like systems, you probably need to think again :) The systems I've seen (and I've looked at a lot of them) are all meant for throughput, not latency. They also have no non-PC I/O. By that I mean that they're usually missing even the parallel port (though some have an internal header for it). We're talking about the controller that actually generates step/dir or PWM signals, and the embedded PCs don't have the connections or the realtime response to do that. They're pretty fast little processors, and if you want to make a little streaming video box they're great, but for the level of realtime performance this project would need, I don't think they can do the job.
Of course I'd love to be proven wrong, so if you know of a little embedded PC that actually has RT latencies <5-10 usec, please tell us about it :) >System based on these can be sourced for less than $100 in bulk and as >an added benefit none of the code needs to be ported. > >Perhaps it's time to experiment with building a custom distro to run >EMC2 or a subset of it on embedded systems booting from flash NAND/NOR. > > This would be excellent. I have a small system that uses RTAI/HAL, and runs from an SSD hard drive. I managed to get the latencies near 1 microsecond most of the time, with outliers around 2 us. This was done by using ext2 on the disk, and preventing almost everything from loading. Additionally, since the PC has a core 2 duo in it, I create a CPU-hog process, which reduces latency from around 5-6 us to around 1us. (I don't know why it works, but this isn't the only system we've seen that on) I would love to have a small distro that just boots up and runs the app (EMC2 or some other RT app), and doesn't barf when you shut it down by removing power (without doing a shutdown). >Instead of porting the code our time might be better spent optimising >for x86 which would benefit all users. > >My main question is how hard would it be to run EMC in a "distributed" >way so that the motion controller could run remotely from the pulse >generator? > > I think the easier thing to do is put the motion controller and pulse generator on the same board, and let EMC2 run remotely the way it was designed - using NML or some other communication method at the CANON level. - Steve ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
