nRF52840 raw RADIO mode: do TXADDRESS and RXADDRESSES imply a hard node-count limit?

[KH0]

Hi, for nRF52840 raw proprietary RADIO mode, do TXADDRESS and RXADDRESSES imply a hard total node-count limit for a custom multi-node network, or only a simultaneous hardware address-matching limit?

I understand RXADDRESSES covers logical addresses 0 to 7, but does that mean the whole network is limited by hardware to 8 peers, or can a larger network still be built if the protocol manages addressing and access in software?

My use case is a custom multi-radio network, not a simple star... In all, if this doesn't provide the node limit, I would like to know if this limit exists and what it is.
Thanks

[Simonr]

Hi

Yes, the TXADDRESS register is a 3 bit register, and the RXADDRESSES is an 8 bit register, so there will be a theoretical max to how many different addresses you can use, but is there a reason they will need different addresses, and how many nodes are you aiming to have in your network? The actual limit should be higher than 8 devices, please see page 601 in the datasheet for more details on how address configuration and on-air radio address fields work.

https://docs.nordicsemi.com/bundle/ps_nrf52840/page/keyfeatures_html5.html 

Best regards,

Simon

[KH0]

Hi Simon,

Thanks, that is helpful. My intended setup is a custom multi-robot network, each using the nRF52840 in raw proprietary RADIO mode (pref), not ESB, Gazell, BLE, Zigbee, or Thread.

The topology I am trying to support is roughly this:

• 1 base station

• around 9 to 20 robots

• robots may need robot-to-robot links as well as robot-to-base links

• so it is not a simple star network

What I am trying to understand is not whether more than 8 devices is theoretically possible in software, but whether the raw RADIO hardware imposes any practical or hard upper node-count limit for this kind of custom network.

More specifically:

does the 8 logical-address mechanism only limit how many addresses one receiver can match simultaneously at a time?

or is there any other raw-RADIO hardware constraint that would impose a total network-size limit for a custom protocol?

Thanks again.

[Andre]

Exactly, that is how many you can be listening for at a given time.

On a sender, you can reconfigure the addresses and send to whatever address you like.

[KH0]

That clarifies the 8 logical-address part well.

So for a custom multi-robot protocol, it sounds like the raw RADIO does not impose a fixed total node-count limit, but rather a simultaneous receive-listening limit per receiver... the practical limit is then mostly determined by protocol design factors such as airtime, packet frequency, retries, latency budget, and how RX address sets are managed, rather than by one fixed raw-RADIO hardware node limit?

thanks

[Simonr]

Hi Emmanuel

That is correct.

Best regards,

Simon