XBee SX 868 for unidirectional RF


I have a setup with one sensor and one collector. The local environment and design constraints of each means the sensor will be effectively TX-only, and the collector will be RX-only. Only sensor–>collector transfer is required.

The collector will potentially have a high-gain antenna to increase RX ability. However, should it transmit it would exceed local ERP TX regulations. As such, it must not transmit.

I have looked through the XBee SX 868 user manual, and I think using a permanent point-to-point setup should be possible to avoid needing a bidirectional handshake/network join. If we never directly ask the collector to transmit, no actual transmit will happen (even as part of the underlying protocol)?

The 10 kbs RF data rate is fine for us - is this likely to result in at least 5 kbs payload data continuous throughput? Is it correct that the XBee will still be using LBT, AFA and duty-cycle-aware protocols under the hood to keep within regulations even in this more “basic” mode and with this continuous data rate?

Many thanks


No that is not true. The module has built in a retry system that requires the receiving side to send back an ACK automatically. I am not aware of any setting that will keep the receiving from possibly re transmitting.

Hi mvut, thanks for your reply.

So even in this basic mode (not DigiMesh etc.) packets will always send an ACK and this cannot be disabled? Not even setting the “Disable ACK” bit on the “TO” AT command?

I think I’m going to need to go with an alternative IC that allows direct 868 radio control and develop our own protocol that will have to do almost exactly what the 868 SX does. What a lot of work!

Thanks anyway.