Probably this has already been answered before. I’m not sure I read it in the datasheet, so am asking: using Shockburst, do those transceiver automatically wait for the channel to be free, before transmitting?
In Chipcon2420 you could check for background RSSI before doing so.
I suppose the answer is “yes” since no other method for checking seems available.
No. The TRW24G does NOT check for on-air collisions.
Hmm, I see.
So, this should mean that in case 2 units transmit at the (exactly) same time, transmission will be scrambled and, in theory, no receiver should get it good, thanks to CRC16 ?
Thanks.
Yes. If two transmitters send at the same time, both transmissions will be messed up, and the CRC will catch it. If you want any kind of reliability you’ll want to come up with your own message acknowledgments.
Yes, I do have my ACK method.
My concern, in this moment, was that I wanted to have some nodes set up as “repeater” , so I was wandering what’d happen if 2 nodes sense the same packet incoming, and try to resend it at the same time.
ACK is something which would come from the real destination address, at a later moment.
networking protocols like IEEE 802.15.4 and 802.11 address data frames to a given network node by a node-unique address: MAC layer device address and optionally, a network layer address. So a node would ignore data frames not addressed to it. Same holds true for ethernet 802.3, but frames aren’t ACKed whereas many wireless protocols ACK each frame due to the higher error rate in wireless.
meshed networks (like ZigBee) relay the frame to a neighbor-node using a routing protocol for wireless, this being an adaptation of wireline protocols like AODV, OSPF, TBRPF - these are IETF RFC standards.
see zigbee.org and vendor websites for 802.15.4/ZigBee.