Mach3, Mach 4 or Linux CNC for G0704

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Originally Posted by ihavenofish

hahahah.. no. just, no. you set up the machine to work as a cnc control, not a web surfing box. you turn everything off. ive never seen any for of "windows" issue running mach3.



timing might be better, hard to say. mach does not have the best timing (hence the misses slow pulses i mentioned), but i dont think thats parport related, or mach related. linuxcnc has much better pulse timing than mach3, and its also just software.



you said grbl. that implies arduino level stuff. theres plenty of higher power systems out there for sure, but they dont cost $9.99 on ebay :) also theres a reason ethernet and usb are not used much and parport is. parport works. sure its slow and limited, but it works. ethernet and especially usb are inherently not realtime. so called realtime ethernet system like my beckhohf ethercat system are not really ethernet as you know it. they use the host tranciever and cable, but its all proprietary protocols. you cant stick your modem or printer on it :)

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Actually there are a number of real time Ethernet systems including Ethernet Powerlink This uses standard Ethernet hardware and supports multi KHz update rates

Our LinuxCNC compatible Ethernet motion cards also use real time Ethernet (standard Ethernet hardware and protocol=UDP) and can support up to 4KHz update rates

The advantage of FPGAs over UCs for pulse generation is cleaner pulse streams (lower subharmonics due to a higher base clock)
scale-ability (we can have up to 64 step generator channels) and higher possible pulse rates (our hardware has a maximum pulse rate of 8 to 25 MHz depending on model)

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ethernet and especially usb are inherently not realtime. so called realtime ethernet system like my beckhohf ethercat system are not really ethernet as you know it. they use the host tranciever and cable, but its all proprietary protocols. you cant stick your modem or printer on it

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Ah, that's a really really old red herring about Ethernet - that it is not 'real time'. Often promulgated by vendors of would-be competing systems. That battle was fought a long time ago, and settled 100%. Ethernet won.

Technically, on the original single 50 ohm cable with ye oldy vampire taps and collision sensing etc (CSMA-CD) the arrival times of packets was subject to some variation. In practice, as measured so often (and published), the delays were extremely small, and packets were NEVER lost because of the packet acknowledgment.

However, with the twisted pair radial/star design used today there are no collisions to worry about. When the ethernet cable is dedicated to driving just the external CNC engine, AND it is ticking over at 100 MHz (or higher), AND you are not trying to surf the web at the same time or having updates in the background, the idea that the ethernet link is not sufficiently RealTime is just plain wrong. Sorry, but just plain wrong.

I have no idea whether the beckhohf ethercat system uses TCP/IP or not. Doesn't matter: modern CNC ethernet connections to things like the Smooth Stepper do use it. Yes, the old parallel port did work - mostly, but it is now obsolete.

Cheers
Roger

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Originally Posted by PCW_MESA

Actually there are a number of real time Ethernet systems including Ethernet Powerlink This uses standard Ethernet hardware and supports multi KHz update rates

Our LinuxCNC compatible Ethernet motion cards also use real time Ethernet (standard Ethernet hardware and protocol=UDP) and can support up to 4KHz update rates

The advantage of FPGAs over UCs for pulse generation is cleaner pulse streams (lower subharmonics due to a higher base clock)
scale-ability (we can have up to 64 step generator channels) and higher possible pulse rates (our hardware has a maximum pulse rate of 8 to 25 MHz depending on model)

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are they "real" ethernet? as in, can i also hook up various computers, modems, printers, etc to the same network?

i was under the impression they all had custom drivers to suit the purpose.

I'm a curious type of guy, so I earlier looked the datasheet up on Digikey and on the UC400ETH there is a 200MHz 32bit floating point uC beast. :)
I really don't want to argue, but I don't really trust on "realtime computers" especially not with commercial OSes like Windows or Linux or anything else which has that level of complexity, but maybe it's just me.
I like the idea of having a buffer better. Probably that involves more development work from the software guys, but it is their problem.

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Originally Posted by ihavenofish

are they "real" ethernet? as in, can i also hook up various computers, modems, printers, etc to the same network?

i was under the impression they all had custom drivers to suit the purpose.

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UDP protocol is one layer below TCP/IP.
Ethernet needs no drivers, but protocols.

I can't answer for the others, but I can answer for the Ethernet Smooth Stepper (as I use one). It uses the stock standard Microsoft Ethernet driver.

However, there is a Smooth Stepper plug-in which takes high-level commands from Mach3 and converts them into ethernet packets. There is also a separate plug-in to convert those same high-level commands from Mach3 into a USB data stream.

Cheers
Roger

Buffers - oh yes, buffers for sure. Won't argue there! You get to specify the size of the buffer you want to use with Mach3 and ESS.
Cheers
Roger

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Originally Posted by OlfCNC

UDP protocol is one layer below TCP/IP.
Ethernet needs no drivers, but protocols.

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Ethernet Powerlink uses standard Ethernet hardware (unlike Ethercat that uses standard hardware on the master but proprietary hardware on the slaves)
but it does use a special driver

Our Ethernet hardware uses standard drivers, protocols, and hardware but like Ethernet Powerlink, requires a RTOS

In either case, standard Ethernet traffic is not allowed on the real time link as it will normally increase jitter to an unacceptable level by
blocking real time traffic

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Originally Posted by PCW_MESA

Ethernet Powerlink uses standard Ethernet hardware (unlike Ethercat that uses standard hardware on the master but proprietary hardware on the slaves)
but it does use a special driver

Our Ethernet hardware uses standard drivers, protocols, and hardware but like Ethernet Powerlink, requires a RTOS

In either case, standard Ethernet traffic is not allowed on the real time link as it will normally increase jitter to an unacceptable level by
blocking real time traffic

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ahh, ok. makes sense.

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Originally Posted by OlfCNC

UDP protocol is one layer below TCP/IP.
Ethernet needs no drivers, but protocols.

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Last I looked, TCP and UDP were both Layer 4 protocols.

Mark

TCP/IP is basicly UDP protocol + error handling and handshake.

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Originally Posted by OlfCNC

TCP/IP is basicly UDP protocol + error handling and handshake.

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Yup, but they aren't on different layers of the OSI model. They're both Layer 4.