| Quote: Originally Posted by BZFrank | | | | |
| The first statement is true but not the second. XPS does not seem to use the IEEE 802.15.4 CSMA/CA (p-Persistance) feature, it just sends its data frames out regardless what else happens on the same channel.
Frank | |
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Well, Maxstream (Digi?) appears to disagree with you on that . . . . .
From the XBeePro documentation:
| Quote: | | | |
| CCA (Clear Channel Assessment)
Prior to transmitting a packet, a CCA (Clear Channel Assessment) is performed on the channel to
determine if the channel is available for transmission. The detected energy on the channel is compared
with the CA (Clear Channel Assessment) parameter value. If the detected energy exceeds
the CA parameter value, the packet is not transmitted.
Also, a delay is inserted before a transmission takes place. This delay is settable using the RN
(Backoff Exponent) parameter. If RN is set to “0”, then there is no delay before the first CCA is performed.
The RN parameter value is the equivalent of the “minBE” parameter in the 802.15.4 specification.
The transmit sequence follows the 802.15.4 specification. | |
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One of the primary features of the wireless stuff is that is does **not** blindly transmit and step on itself - that's how multiple devices can exist on the same channel cleanly!
- Tim