On Tue, Jul 28, 2009 at 9:27 AM, Rémi Villé<[email protected]> wrote: > Hi, > > TOSH_DATA_LENGTH is about 20-30 byte, depending of the mote. I have read > that we can increase this value to something like 100 byte. > But what would be the reason to choose a 100 byte payload rather than a 30 > byte one ? > I mean if I have 100 byte to send, should I send 4 packet of 30 byte ? Maybe > because if there's one error in the message (CRC detection) I should > retransmit 100 byte rather than 30 byte... > > I don't know which is the best way to choose a good TASH_DATA_LENGTH > (assuming that I have an infinite number of byte to send), maybe by > experimentation or by analyzing? or maybe the default length has been chosen > with this considerations? >
if you had infinite bytes to send I suspect the best choice would be the largest possible payload size. For 802.15.4 radios this is 128 bytes, but TOS adds some extra headers. I think you can go up to around 120 bytes for TOSH_DATA_LENGTH, you should verify this number to be sure. See this thread also: https://www.millennium.berkeley.edu/pipermail/tinyos-help/2009-May/040012.html I don't know exactly how the 30 byte default was chosen but I suspect it was chosen to provide 'enough' data for many sensor network applications while being small enough not to use up a not of memory on the mote. Since TOS is statically linked every message_t must hold TOSH_DATA_LENGTH bytes (plus some headers). _______________________________________________ Tinyos-help mailing list [email protected] https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
