Leopold Palomo-Avellaneda wrote: > A Dimarts 20 Març 2007 15:50, Jan Kiszka va escriure: >> Leopold Palomo-Avellaneda wrote: >>> A Dimarts 20 Març 2007 15:00, Jan Kiszka va escriure: >>>> Leopold Palomo-Avellaneda wrote: >>>>> ... >>>>> Ok, >>>>> >>>>> thanks for the answer. I have to addmitt that to me all the >>>>> documentation is a bit confuse for someone that begins in this area. >>>>> Although there are a lot documents, I'm a bit lost. >>>> That's what we are gradually trying to improve via the wiki. Work in >>>> progress, contributions of any form are welcome. >>> a Readme first ... >> What information are you missing in the existing top-level readme? > > Well first of all please I have to agree all you effort (and the others > developers) in the rtnet. To me the main problem is the begin. I'm not an > expert in realtime and I'm doing this for a work in my phD using only the rt > as a tool, not as target. > > Mainly, although I have a rtnet configured and working I'm not sure what I'm > doing. Probably is my problem because the lack of knowledge in this area and > the nomenclature or the concepts are a bit unclear to me. Basically I need a > step 0 or step -2 to begin. In the top-level readme I found: > > > What is it? > .... > ... RTmac layer > > I don't know what is a RTmac layer
"Access to nondeterministic media is managed by the pluggable RTmac layer and the actual control discipline." > ... > and I don't know what is a TDMA Ok, that's improvable. > > What are the requirements? > ok > > How to install it? > ok > > How to test it? > > 3. Check <PREFIX>/etc/rtnet.conf and adapt at least the following parameters: > RT_DRIVER, IPADDR, TDMA_MODE, TDMA_SLAVES. > > maybe an example of configuration (or I didn't found it) with two boxes with > cross cable, tree boxes an a hub, n-boxes and a hup... That's intended to be derived from the additional in-place comments in rtnet.conf. > > Special notes > 3. Configure real-time NICs: rtifconfig rtethX up <IP>, > rtifconfig rtlo up 127.0.0.1 > 4. Add host routes to target nodes, either explicitly: > rtroute add <target IP> <target hw-address> dev <local NIC> > Or trigger an ARP handshake: > rtroute solicit <target IP> dev <local NIC> > > in a normal net I don't need to add a node if it has a local address, maybe a > point that it's necessary in the rtmodule (or I have understand it) RTnet implements "static ARP", which means that ARP requests need to be triggered manually and that ARP table entries do not automatically expire. > > > [.....] > >>>> If you picked the default setup via rtnet.conf, TDMA was activated at a >>>> cycle period of 5 ms, one transmission slot per node and cycle. Thus you >>>> get a latency of up to 2 x 5 ms. >>>> >>>> You can improve this by reducing the period or adding more transmission >>>> slots per cycle. If you only want to use the RTnet link for RT traffic >>>> and you have a collision-free media (cross-link or switched Ethernet), >>>> you could also run RTnet without RTmac/TDMA. Writing a specialised RTmac >>>> discipline (as a replacement for TDMA) is yet another option, but surely >>>> a more complex one. >>> Ok, I only want a simple thing. The problem is that I need the fastest >>> low latency response as I can. I have only to send some bytes, no a lot >>> of info. >> Then you probably want plain RTnet without RTmac/TDMA. > > so I throw away the tdma.conf file and I only wotk with the rtnet.conf. Through rtnet.conf away as well, switch to "Starting the RTnet core manually (without RTmac)" from the README. > >>> You comment something about to modify the tdma.conf file. I have this >>> parameters: >>> >>> master: >>> ip 192.168.1.3 >>> cycle 5000 >>> slot 0 0 >>> slot 1 100 >>> >>> #slave: >> ^^^ >> This comments out the slave section mark, thus breaking the syntax. > > yes, I did a mistake!!!!!! > >>> ip 192.168.1.3 >>> #mac 00:C0:3A:25:01:OB >>> mac 00:A0:C9:1D:52:B9 >>> slot 0 2400 >>> slot 1 2200 2/2 >>> >>> but I don't know if this are correct or not. >> The fragment above is for demonstration of the tdma.conf language. See >> Documentation/README.rtmac for details about what those lines express. >> >>>> However, it all melts down to scheduling your network traffic for hard >>>> real-time use, not to make it simply as fast as possible, but to make it >>>> fully predictable. >>> Yes I know, but is a simple system: a PC with rtai and rtnet and a robot >>> controller with vxworks. >> This doesn't tell anything about the communication structure, the timing >> of your system, or the closure of the control loop (if there is any). > > Well, I have a rtai box with orocos [1]. The idea is that here we will > implement a software controller of a robot. In the other part (the vxworks) > we have the controller of the robot. However we have a library that let us > send the torque to each joint and read the position of the jooint. The > controller says that has a close loop of 4 ms. So the idea is that in this > time, we could read the positions of the robot, send then to the > rtai-controller and read the torques to apply to the robot. All of this is > thinking that we can do the control in one milisecon in the rtai-controller. So you need RTnet to talk to the VxWorks box on the robot or/and to build a distributed robot controller over multiple RTnet nodes? Jan
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