Very interesting topic! Kenneth Lerman wrote: > Is 100BaseT ethernet full duplex? (I think it is.) > > That's easy to find:
sudo mii-tool Password: eth0: negotiated 100baseTx-FD flow-control, link ok FD = Full Duplex > In principle, one could make a "hub" (not technically a hub) that daisy > chained cables. So, the master would output to slave 1 abd input from slave > N. Slave 1 would input from the master and output to slave 2. Slave 2 would > input from slave 1 and output to slave 2... Slave N would input from slave > N-1 and output to the master. > > That's daisy chain isn't it? The trouble is that low cost encoder won't handle traffic for advanced motor or whatever controllers. > Each slave would read its input, process it if appropriate and pass it on to > the next in the link. It would also inject its output into the ring. > > Think of it as a token ring using ethernet hardware that is cheap and > readily available. > > The master would continuosly send poll packets around the ring. > > Mix of high and slow devices is asking for trouble IMO. My preference would be to have individual connections to machine components based on speed. Perhaps using two buses, one for slow devices and one for faster ones. Industry offers a number of hardware solutions for digital IO mentioned on this mailing list. Some could be adapted for handling bus type communications between PC and peripherals. However, they are not standardized with number of IO lines, buffers, number of registers, protocols, open source/architecture, etc. This brings up another option, build an open source EMC controller PCI[e] card with slow, medium and high speed ports that could be used to control buses. Speeds would need to be determined based on what is required for machine world. If build with an FPGA, it would be very flexible and handle a lot of logic and speed and could be programmed for different needs: use with lathe, 3D routers and torch machines, or even run real time functions. It would be easier to have one "programmable" card that would connect to most sensors, encoders, etc. than to find encoders and other such stuff with ethernet built in. I know, I'm asking too much, who has time and resources to build all this :-) > An alternative is to use a standard hub and have the master poll each of the > slaves, in turn. > > I don't see this as something to use with encoders, but I could imagine its > being used with smart motor controllers or multi-axis controllers (like > Jon's). > > In either case we are looking at significant change from current more or less standard parallel port. For now it's easy to find PCI cards with parallel ports which is good for the time being. PCI bus will soon be replaced with PCIe. Will that bring cards with parallel ports is yet to be seen. Even then, parallel port is just not the right thing. It was never meant to be used for anything fast not to mention electric and mechanical characteristics of the port. I don't think ethernet components will be low cost enough to attract home builders to it for a while so we'll keep looking for low cost IO ports. > Ken > Good job all of you guys out there. I learn a lot from you every day. -- Rafael ------------------------------------------------------------------------- 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
