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Thread Closed: Became flame-war

???
04/17/08 08:05
Modified:
  04/17/08 08:08
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 		 #153597 - Listen Before Xmit ......
Responding to: ???'s previous message
Jack said:
Are you using frequency hopping, or at least using separate frequencies for transmit and receive?

Andy said:

How will each one "know" which slaves to scan...?


I am using DSSS transceiver with 13 channels, till date I have programmed my Chipcon parts (now texas) in a way that if a master speaks only the slaves listen . The masters use random seed and scan the channel before transmit , if it finds channel empty it transmits a beacon (now slaves listen to it). The master doesnt knows any slaves address at all as the phenomenon is random in process . Now the slave registering part has to be dealt with without much collisions in some effective way .
Andy , Slaves are shared by all the masters , master just have to register them when slaves starts to broadcast in some way , which is the point of discussion . If it had been a POLLING issue it doesnt require any discussion as the polling stuff is streight forward .

Jack said:

As for polling listeners, one approach may be to adapt the technique used in ARP (address resolution protocol) from tcp/ip. At periodic intervals have each slave advertise its address, similar to the ARP Announcement used to tell ethernet switches the subnets used on each port. You might want to read about how ARP (and ICMP) protocols work for some ideas.



I will have alook at how ARP is implemented , Collision will increase with this approch I guess , or we have to enable slaves with collision avoidance algorithm , if they go on by their own , what Erik says " picosecond stuff" will happen many times .

Andy Neil said:
http://www.edn-europe.com/rfmodules...urope.html


I have started .

Ap

List of 115 messages in thread
TopicAuthorDate
Wireless network            01/01/70 00:00      
   assign address to each slave?(with "jumpers")            01/01/70 00:00      
      Still you wont know which is which?            01/01/70 00:00      
         pay with time            01/01/70 00:00      
            not easy            01/01/70 00:00      
            or pay with money            01/01/70 00:00      
               or pay with money - not a solution            01/01/70 00:00      
                  Inherently not simple!            01/01/70 00:00      
         you cant poll for N number of slaves            01/01/70 00:00      
             automatic            01/01/70 00:00      
               N?            01/01/70 00:00      
                  N? - any            01/01/70 00:00      
         Ho about this ...            01/01/70 00:00      
            how do you propose to do that?            01/01/70 00:00      
               have a look at the picture on the website            01/01/70 00:00      
                  Obviously missing something here...            01/01/70 00:00      
                  dipswitch my butt            01/01/70 00:00      
                     it\'s pretty obvious, isn\'t it?            01/01/70 00:00      
                        first - then            01/01/70 00:00      
                           Once again you're assuming facts not in evidence            01/01/70 00:00      
                              The sample is much larger now            01/01/70 00:00      
                                 example            01/01/70 00:00      
                                    Yes, it is            01/01/70 00:00      
                                 I like that ...            01/01/70 00:00      
            I Don't get it either.            01/01/70 00:00      
               It's reall not that complicated ... but ...            01/01/70 00:00      
                  Still not with you            01/01/70 00:00      
                  Slaves to broadcast their presence HOW?            01/01/70 00:00      
                     Not that difficult            01/01/70 00:00      
                        Thats fine but what if we have            01/01/70 00:00      
                           Then you really do need a database!            01/01/70 00:00      
                              you WILL get in big doo-doo            01/01/70 00:00      
                                 this is absolutely true!            01/01/70 00:00      
                           You\'ll need lots of switches and lots of ports            01/01/70 00:00      
                              totally off the rocker            01/01/70 00:00      
                                 How long, at 8kbps            01/01/70 00:00      
                                    Who on Earth wants to do that            01/01/70 00:00      
                                       One has to set limits            01/01/70 00:00      
                                          It does not have to be manual            01/01/70 00:00      
                                             It has its "baggage"            01/01/70 00:00      
                                                no "significant burden" who cares about 'simpler'            01/01/70 00:00      
                                                   Maybe we need to bring the O/P back to reality            01/01/70 00:00      
                                                      I can't tell            01/01/70 00:00      
                                                         I may be slow today....            01/01/70 00:00      
                                                   ARP possiblities            01/01/70 00:00      
                                                Overhead - but possibly not too serious?            01/01/70 00:00      
                                                   You may be onto something ...            01/01/70 00:00      
                                                      you don't get it            01/01/70 00:00      
                                                         How long would it take?            01/01/70 00:00      
                                                            quicker than what?            01/01/70 00:00      
                                                               Obviously there's a trick involved            01/01/70 00:00      
                                                                  or ...            01/01/70 00:00      
                                                                     no patent ...            01/01/70 00:00      
                                                                        With that scheme you have to skip some            01/01/70 00:00      
                                                                           easy            01/01/70 00:00      
                                                                              No ... it means there's nobody at that one address            01/01/70 00:00      
                                                                                 Not an address, an address mask            01/01/70 00:00      
                                                                                    not likely on low-cost RF            01/01/70 00:00      
                                                                                       of course, but nobody woud dream of sending RF w/o            01/01/70 00:00      
                                                                                          Miracle ? , I differ            01/01/70 00:00      
                                                                                 confound it reat the stuff            01/01/70 00:00      
                                                                        no patent ... And after slaves colliding            01/01/70 00:00      
                                                                           after each 'find' it get faster            01/01/70 00:00      
                                                                              the cheap RF links are typically            01/01/70 00:00      
                                                               Erik, please clarify one point            01/01/70 00:00      
                                                                  If one could devise a suitable RF protocol...            01/01/70 00:00      
                                                                     the key is to know more than is known here            01/01/70 00:00      
                                                                        confound it can't you read            01/01/70 00:00      
                                                                           You're assuming facts not in evidence.            01/01/70 00:00      
                                                                              if a response comes, your code is faulty            01/01/70 00:00      
                                                                                 So ... how does that differ from not transmitting?            01/01/70 00:00      
                                                                                    Richard, Richard            01/01/70 00:00      
                                                                                       Yes, but what SHOULD happen?            01/01/70 00:00      
                                                                                       with a mask of zero any unassigned sign sho            01/01/70 00:00      
                                                                                          What is it you are recommending, Erik?            01/01/70 00:00      
                                                                                             Nothing I feel            01/01/70 00:00      
                                                                                             Reading Erik's mind            01/01/70 00:00      
                                                                                                Address+Mask - an RF twist            01/01/70 00:00      
                                                                                                   let me clarify            01/01/70 00:00      
                                                                                                Russ, I admire your "psychic abilities'            01/01/70 00:00      
                                                                                                   A refinement            01/01/70 00:00      
                                                                                                      yes            01/01/70 00:00      
                                                                                                         Starting over            01/01/70 00:00      
                                                                                                            Russ, you may very well be right            01/01/70 00:00      
                                                                                                   Erik, that is not what was asked for!            01/01/70 00:00      
                                                                                                      whic i would have done ...            01/01/70 00:00      
                                                                                                         Perhaps you\'re not aware ...            01/01/70 00:00      
                                                                                                            1) abd 2)            01/01/70 00:00      
                                                                                             NOT "mask address" but "mask AND address"            01/01/70 00:00      
                                                                        some things you can do on the one-wire channel            01/01/70 00:00      
                                                                           Very tricky indeed            01/01/70 00:00      
                                                                              I do not ASS U ME diddlysquat            01/01/70 00:00      
                                                                           It is absolutly required for my scheme            01/01/70 00:00      
                                                                              That is a non-starter with low-cost RF.            01/01/70 00:00      
                                                                  sorry            01/01/70 00:00      
   OK, here's an idea            01/01/70 00:00      
      collisions avoidance ?            01/01/70 00:00      
         Surely the master needs to know its slaves?!            01/01/70 00:00      
            identifying slaves            01/01/70 00:00      
         I can not help with collisions but..            01/01/70 00:00      
   multimaster via RF            01/01/70 00:00      
      collision recovery            01/01/70 00:00      
         Not a few seconds            01/01/70 00:00      
         Listen Before Xmit            01/01/70 00:00      
            not that urban legend again            01/01/70 00:00      
               Accepted terminology            01/01/70 00:00      
            Collisions will still happen            01/01/70 00:00      
               Yes, but how will the system respond?            01/01/70 00:00      
            Listen Before Xmit ......            01/01/70 00:00      
               if slaves can "speak without being spoken to"            01/01/70 00:00      
   Perhaps you should read this article            01/01/70 00:00      
    A Better Way             01/01/70 00:00      
      There are some internal issues too            01/01/70 00:00      
         frequency hopping            01/01/70 00:00      
            frequency hopping , I have DSSS            01/01/70 00:00      

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