Re: silly ravenscar question

[jan.de.kruyf@gmail.com]

On Tuesday, February 24, 2015 at 12:29:02 PM UTC+2, Dmitry A. Kazakov wrote:
> On Tue, 24 Feb 2015 01:07:31 -0800 (PST), jan.de.kruyf wrote:
> 
> > I am busy doing a very light ethernet fieldbus for a few Olimex stm34 boards and a pc.
> 
> You mean the boards will be sort of terminals. And the master will be?
> Which cycles you are talking about, 1ms, 0.1ms, 0.01ms?

Pc, havn't dug into that part yet. I was going to use Proview scada/plc with powerlink, but there is a sizable custom section in my code. So its 'to be decided' at the moment.
I am aiming for 1 msec cycletime, but if it comes out at 2 I will also be happy. Remember STM runs only at 168 Mhz. 


> 
> EtherCAT does not need special hardware. If you mean Beckhoff's piggyback,
> you don't have to use it. You can do all it does with a plain board and raw
> Ethernet. Admittedly it would be a lot of work and EtherCAT slave protocol
> (all upper levels) is a horrific mess.
> 
yes I know, but then the timing advantage is virtually gone. And you are very right about the mess. I sorted a Beckhoff installation with comms issues a few years back. I  was on the phone to Germany daily, but I got send around in circles. From this supplier to that one to that one. . . .
So in the end -I- sorted it. Help from any of them was well below standard. 

> > Is there any interest in the community? I am willing to put it under GPL.
> 
> If that would not hinder selling the terminals to the end customers without
> exposing the sources...

You raise an interesting point. Do I give things away then for everybody to get rich with? . . . 

> 
> All existing fieldbuses are extremely poor designed, in my view. But I
> doubt it would be a work for one man.

[Begriffe, welche sich bei der Ordnung der Dinge als nützlich erwiesen haben, erlangen über uns leicht eine solche Autorität, dass wir ihres irdischen Ursprungs vergessen und sie als unabänderliche Gegebenheiten hinnehmen.]

from: http://en.wikiquote.org/wiki/Albert_Einstein

So it took me a week of sweating to get to the depth of that truth, but now it looks rather doable.

So, did you work at all with the gnat ravenscar package for STM, Dimitry?


cheers.

j.