Reliable communication.



  • I know, there are tons of threads on this subject.
    Most of them are old, back on 1.5.*
    I have some nodes. The messages arrives 95% of the times. I would like 100% 🙂
    I know, more repeaters might help but i have 4-10 meters between my nodes and my gateway.
    Is it possible to acheave reliable communication?
    I've seen examples on resend, but is there a "right" way to do it? It seems you have to do it different depending of what type av node it is?
    I am on 2.1.1 right now. Are there any difference in 2.2.0 in this area?
    Other stuff is often very well explained. Like how to connect stuff and the battery measurement part is so easy with pictures like a child could understand it.


  • Hardware Contributor

    Hello, @xydix

    you should not have any problem for such a short distance.
    Before checking acks and retrying to send I would check those:

    • problem with radio quality: what modules do you use on nodes and gateway ? Did you set the TX power to PA_MAX ?
    • problem with interferences: what channel do you use ? have you tried one of the channels outside of the wifi frequency ? (>=100)


  • I did notice a remarkable increase in performance upgrading to 2.2.0, especially downlink. It is worth a try.



  • @nca78 said in Reliable communication.:

    Hello, @xydix

    you should not have any problem for such a short distance.
    Before checking acks and retrying to send I would check those:

    • problem with radio quality: what modules do you use on nodes and gateway ? Did you set the TX power to PA_MAX ?
    • problem with interferences: what channel do you use ? have you tried one of the channels outside of the wifi frequency ? (>=100)

    I got som concrete walls that might block the signal a little.
    For my gateway I use this radio. Bought it after watched a YouTube video, a guy compared radios.

    In my nodes I use various radios. Some bought from eBay, aliexpress, electrodragon.
    I tried different capacitors, some antenna mods.
    All nodes us PA_MAX. Gateway is low I think.
    My problem is receiving messages from nodes.
    I haven't changed the channel.
    It is so hard to know when a test/change give results. I might have a missed message once a week or something like that. This is based on when one of my motion sensors showing motion for a long time and there is no motion.
    A resend function solves the problem even if the actual problem is the hardware.


  • Hardware Contributor

    @xydix this is a good radio from EByte, but if "Gateway is low I think" means you have a lower power setting then you're not making use of the PA/LNA on that radio which is a shame. I have a similar radio, with 25-30cm thick concrete walls and signal manages to go around the walls.
    So I would check the power level of the gateway first, and if it doesn't solve the problem then you have to implement the resend, but no there doesn't seem to be a "right" way to do it. You just need to :

    • make sure ACK is enabled for the node (I think there is an automatic resend implemented in radio in this case)
    • check result of the send command, and if false sleep a little bit and send again, you can do this in a loop to try sending a few more times.


  • @xydix I had also problems with reliable comunication using nrf modules. I switched to rfm69 and it is much much better. It is easy to switch to rfm69 using this: https://www.mysensors.org/hardware/nrf2rfm69. But appart from that a good resend algorithm is also necessary. Unfortunately there is no one good resend algorithm for every use case, it depends on the node usage.



  • I have to second the RFM69 modules over the NRF modules. I was struggling to get more than about 7 metres in open air on the NRF modules that I had, however swapping over to trying the RFM69 modules for me will get me 30m distance through 2-3 brick walls with no hassle at all. I haven't looked back 🙂



  • @chester It is worth emphasising that there are huge differences in object penetration and range between 2.4GHz and for instance 433MHz, before considering how cluttered and noisy the wifi band has become in recent years, even in my own country village setting.
    My only Wifi connection from the monitoring system is collecting Internet data and remote viewing, all Gateway and Node comms are via the RFM69s which have proven completely reliable.



  • Yes, I believe that the frequency is the key factor here. Additionally, the RFM69 provides RSSI reading so it is much easier to troubleshoot connection problems.



  • @nca78 said in Reliable communication.:

    @xydix this is a good radio from EByte, but if "Gateway is low I think" means you have a lower power setting then you're not making use of the PA/LNA on that radio which is a shame. I have a similar radio, with 25-30cm thick concrete walls and signal manages to go around the walls.
    So I would check the power level of the gateway first, and if it doesn't solve the problem then you have to implement the resend, but no there doesn't seem to be a "right" way to do it. You just need to :

    • make sure ACK is enabled for the node (I think there is an automatic resend implemented in radio in this case)
    • check result of the send command, and if false sleep a little bit and send again, you can do this in a loop to try sending a few more times.

    I had my radio on high or max at first but experience it more stable now. After all, everything i send out from my gateway is ok. I have problem receiving from my nodes.
    Today i do not use ack on any node.
    May it be enough to enable ack to make the node try again if it doesn't receive the ack back?

    @rozpruwacz said in Reliable communication.:

    @xydix I had also problems with reliable comunication using nrf modules. I switched to rfm69 and it is much much better. It is easy to switch to rfm69 using this: https://www.mysensors.org/hardware/nrf2rfm69. But appart from that a good resend algorithm is also necessary. Unfortunately there is no one good resend algorithm for every use case, it depends on the node usage.

    I started with nrf because I was to cheap to buy RFM69, and didn't know if mysensors was something I would like.
    Then there was a lot of different versions, so i went for the NFR because it was easy. I am pretty happy with it but it isn't 100%.
    What should i choose? 433 or 868? Do they both got same features?



  • You should choose the one that is legal in Your country. If both are legal I would go for 868 because it requires shorter antenna.



  • How about RFM69W? 13dBm And RFM69HW? 20dBm. Wich one for battery nodes? Are there more alternatives? Have i seen a RFM69C somewhere? HW for the gateway?



  • use only RFM69W. RFM69HW has additional power amplifier on TX but the RX side is the same so there is no benefit, maybe You will have better link from GW to the nodes, but from the nodes to the gateway it will still be the same as for RFM69W.



  • @xydix The lower power you can use the better, particularly where battery powered.
    You can see the size differences between the W and the CW on the lowpowerlab link below, but note that W and HW are pin compatible, CW and HCW are not...
    link text


 

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