Radio network questions

[delivereath]

Hi all,

I'm interested in creating a mysensors network to add some sensors that are currently missing on my z-wave home automation network.

Regarding the radio, I will probably use the RFM69 at 433MHz. I've seen that the nrf can be set up to act as repeater-sensor node. Is that also available on RFM69 ?

Regarding general sensor power consumption, do they only transmit RF data when the sensors or repeater has a real value to transmit to the gateway or is there any general metadata to send that requires regular packets to be sent ? In other words, if I have a temperature sensor sending only data when there is a temperature change, is it true to say that there won't be any radio activity if there is no temperature change ?

Last question, is it the gateway that requests values from the sensors (with no risk of collisions) or do the sensors send data to the gateway as soon as it is available (with risk of radio collision) ? Or is the protocol smarter than this ?

Thanks !

[mfalkvidd]

Welcome to the MySensors community, @delivereath!
If you haven't already, check out https://www.mysensors.org/about/network

Regarding the radio, I will probably use the RFM69 at 433MHz. I've seen that the nrf can be set up to act as repeater-sensor node. Is that also available on RFM69 ?

Yes. It works the same way for nrf and rfm. https://www.mysensors.org/download/sensor_api_20#create-repeating-nodes has more information.

Regarding general sensor ower consumption, do they only transmit RF data when the sensors or repeater has a real value to transmit to the gateway or is there any general metadata to send that requires regular packets to be sent ? In other words, if I have a temperature sensor sending only data when there is a temperature change, is it true to say that there won't be any radio activity if there is no temperature change ?

All nodes check the network connectivity at startup. It is possibe to enable heartbeats, but they are not enabled by default. Except that, nodes will only communicate when receiving and sending messages.

Last question, is it the gateway that requests values from the sensors (with no risk of collisions) or do the sensors send data to the gateway as soon as it is available (with risk of radio collision) ? Or is the protocol smarter than this ?

Any node is allowed to send a message at any time, so it is up to you. Messages are short and MySensors is not meant for streaming data so the risk of collision is low. All messages are acknowledged and re-sent a few times if acknowledgement fails.

[hek]

@mfalkvidd said:

All messages are acknowledged and re-sent a few times if acknowledgement fails.

Only true for RF24.

RFM69 has no build in hardware inter-node re-transmission mechanism. But as @mfalkvidd says, the risk of collision is low. For really important message such as light switch status etc, you could enable the software ack for the message (and handle re-transmission yourself if no ack is received within an acceptable timeout).

EDIT: Sorry, @tekka did just spanked me up. We have software inter-node ack for RFM69 nowadays.

[delivereath]

Hi !

Thanks for these detailed answers. Everything seems well designed. Looking forward to receive my hardware and be able to get my hands on.

[Mihai]

@hek
Please let me know if in v.2.1.0 the ACK is enabled by default for NRF24 or if we may enable/disable it (where?).
Also I am interesting about the retain flag management from the gateway toward the mqtt broker: is it possible to manage it? How?
Thank you