Modern Ethernet does not have a collision problem. It uses a switched topology. All of the cables are point to point. One end is on your device the other is on a switch. The switch has enough performance and bandwidth to drive all cables at full wire speed.
The switch adds very little latency. Modern switches (if they can) do not buffer the entire Ethernet packet as the older first generation switches did. They now will read the packet header and pick off the "to" address then cut the bits over to the correct outbound cable. For sending data to 18 different motors, Ethernet would work fine, Use a 24 port switch. I have a small robot arm that is controlled by 7 channels of PWM. I use a single chip device that has 16 PWM output pins and uses i2C input. Cost is under $5 It would be easy to use two of these chips but the resolution is poor I can control the PWM duty cycle only to about one part in a thousand. The over the bus protocol is defined by the chip maker and I have no choice but to use that. On Thu, Jun 1, 2017 at 12:04 AM, Nicklas Karlsson < [email protected]> wrote: > > If Ethernet is "complex" then PowerLink is "very complex" as it is a few > > layers over top of Ethernet. > > > > Is there a list of requirements some place? What are the end points, > > processes that run on a CPU of some kind. > > > > I've been doing this kind of work for ages but you can't select anything > > without a detailed set of requirements > > It is rather simple to send or receive via UDP/IP or TCP/IP for example > via Ethernet. UDP/IP is one way packets. TCP/IP send acknowledge which add > bandwidth requirement in the opposite direction. To make sure packets > within a particular time period may however be harder. > > Then sending point to point over an ordinary serial channel like UART or > SPI data usually arrive practically instantly and there are no collisions. > UART or SPI is also very cheap. Software for simple point to point may also > be very simple. A bus have huge advantages then it come to number of nodes > but there may be collisions. > > Even though collisions are a small problem to make it work perfect during > periodic communication may be surprisingly hard while for a simple serial > channel it is no problem at all. > > > Regards Nicklas Karlsson > > ------------------------------------------------------------ > ------------------ > Check out the vibrant tech community on one of the world's most > engaging tech sites, Slashdot.org! http://sdm.link/slashdot > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Chris Albertson Redondo Beach, California ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
