| ??? 04/18/08 05:37 Read: times |
#153653 - Maybe we need to bring the O/P back to reality Responding to: ???'s previous message |
Erik Malund said:
If it's internally stored, it places a significant burden on manufacturing, as they have to track which addresses have been used and ensure they're NEVER used again.
no "significant burden", just put a DS2411 on the board and let Maxim do it for you at a cost of $0.33 I agree, though, that if you decide to use that scheme, it IS simpler for the end-user. who cares about 'simpler' as Andy said If users can fiddle with it, then they will mess it up sooner or later! It increases the initialization time from several seconds to many hours, though, since it takes a while for the master to poll 2^64 addresses, waiting for all responses, then recording and tabulating the non-nil ones. nope, it's quite fast. With the proper algorithm you can 'find', say, 64 slaves (each with a 48 bit address) in about 2 seconds. Then assign them an 8 bit 'node address' Given that you have 10 billion possible addresses, and know nothing about which ones might or might not be used on your syste, how long does it take this scheme to ferret out all the possible stations at 8 kbps (a maximal rate limit common in low-cost RF hardware)? Clearly that would force some more complex protocol, with the baggage that brings with it, as polling is, under such conditions, far too time-consuming.
the remainder is based on 48 bit node address, max 250 nodes (with random 48 bit addresses changed by a boot routine to 1 byte) Perhaps, but he's stated that he has to use 10 billion addresses, not just 250. How does one cope with that? Once you have your "node list" it does not need to take more than the time for 2 bytes out and 1 byte in to poll.
Erik It looks to me as though the problem has been overstated by several orders of magnitude. Given his stated range, 10 billion addresses, which would have to be processed by each and every "master" combined with the low data rate, I'm persuaded that it will still take quite a while to determine how many slaves there are and what their functional characteristics are. Of course, I'm looking at this from the standpoint of the master, and you've apparently focused on the slaves. The DS2411 won't help make things happen any faster, though I'd like to see what sort of algorithm one might use to perform an exhaustive search of the entire range of addresses required. I suspect he doesn't really need 10 billion ... RE |
