Maybe like $7 then connected via SPI with integrated driver. Integrated in 
micro controller is cheaper but then two drivers are required which increase 
price.

For $1 - $3 it is possible to get good micro controller for control of hardware 
(servo motors), the more expensive is needed then driving display or similar 
tasks. Digital IO is really simple.

They are both in a little bit higher quantity but not very high quantity. It's 
a big difference for electronic circuits but if five is needed for a machine 
it's not much money for a machine. If it had any difference on quality I would 
definetely pay tenfold 10*5*$5=$250 extra instead of the current cost of 
55*$5=$25 for five of these.

I tried ordinary Ethernet, it seems to work perfect then connected with swtich 
between driver cards and computer but I am still prepared not confident it 
always will so I am prepared to spend the extra effort and threw away these 
cards.


Regards Nicklas Karlsson



> What is the cost of an Ethercat chip ?
> 
> Dave
> 
> On 10/24/2017 11:48 AM, Nicklas Karlsson wrote:
> >> Hardware for master is hard to find because you don't need it.   Any normal
> >> Ethernet port works.   Master is a software-only solution.
> > Time triggered transmit would be useful to get perfect timing and fully 
> > utilize bandwidth.
> >
> >> You can choose a simple less redundant network topology.  Double ring is
> >> used because it can tolerate failure and it's not more expensive then daisy
> >> chain.
> > Double ring is two daisy chains in opposite direction and I expect it to 
> > two almost twice as exensive except the cables. Even though I do not use I 
> > can't find a chip with only direction one direction. The Ethercat cost 
> > somewhere in between 2-5 times as much as a micro controller for the 
> > hardware which would be a problem for a low cost product but for me and 
> > probably most other quality is more important.
> >
> > Most important is working principle similar to cascade coupled shift 
> > registers, it's simple and there are no collisions. Principle is similar to 
> > cascade coupled shift register, I guess at each node last value shifted out 
> > would be the CRC checksum. Micro controller with CRC hardware for SPI would 
> > probably handle this but with limitations on where data is inserted and not 
> > the least no differential signals.
> >
> > Even though Ethercat chip is relatively expensive compared to other 
> > components I will pay the money because in the large picture it's little 
> > money. Because of this they might have created something that could earn 
> > them very good money.
> >
> >
> > Nicklas Karlsson
> >
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