Photon + XBee Digi MESH


#21

I set the radios to send data every 250 milliseconds, four times a second.

The Gateway is receiving 12 messages per second and sending 12 replies on every receipt.

So the Gateway is processing 24 TX/RX events per second!

It’s crazy to see how quickly these continuously process info :slight_smile:


#22

Found this data in the manual for these radios as far as data rates.


#23

If you look on the Digi forums there are a lot of posts with people trying to replicate these numbers without success. In my own experience I can’t get any higher than ~43kbps. I call shenanigans on 91Kbps…


#24

With these exact same radios?


#25

Yes


#26

In case any one reading this is interested – I am selling a bunch of used Digi radios: https://www.ebay.com/itm/264091022783

As mentioned in the Ebay listing, no warranty on these, but they would be good for prototyping.

We ultimately decided to use Particle Electrons in place of Digi radios :man_shrugging:t3:


#27

Looks it could be a good deal for somebody.

These 900mhz units have been up and running non stop for a week with no issues running at 12 messages a second.

The Electrons can be perfect in a lot of situations so I’m not surprised you switched to them.

What kind of range were you trying to cover with the 2.4 GHz XBee radios?


#28

They were 500-1000ft away from each other with clear line of sight and a mesh topology.

For the most part they worked OK, as long as the network had less than 25-30 nodes. Once we went above that level the network became very unstable – i.e. a crash at a single node would take down the full network for a while. After lots of debugging and whatnot, we finally got on the phone with Digi tech support, and they said their mesh networks stop working well above 30 or so nodes, unless you follow a very specific setup process and split the networks.

The product we sell can’t have that type of strict setup process or that type of unreliability, so we started looking elsewhere and found the Electron. If we ever go down the local radio network route again, it would be with something with long range and hub/spoke topology, like LoRA.


#29

Interesting, I’ve never heard this before.

What mesh topology were you using? I’m using Digimesh where all Nodes are routers.

Were your radios always powered ON or did they go into sleep modes?

I started playing with LoRa radios first and didn’t really like them near as much as the Digi 900 radios as I found the Digi radios had better support and software code to go along with them, and many books written explaining how to use them.


#30

My opinion on LoRA is probably heavily influenced by “grass is greener” type thinking, so take it with a grain of salt. However, I do think field setup of a hub/spoke topology is much easier and more understandable for a third party. Our product is something we have others install for us, so we need that type of ease of use and troubleshooting.

When implementing XBee radios, they were reliable up to 30 or so devices on one network. Past this level I tried all methods I could find to get them working. 75% or so of my radios were nodes asleep most of the time, with the remainder awake and in router mode. We had two radios in base station node in order to help manage the network – if I remember correctly one for receiving data and the other for managing the network.

Ultimately, ease of setup and troubleshooting became big concerns for me with XBee, so we went down another route. If our use case was limited to 30 or less radios, we may still be using XBee. To me, mesh is a little like magic, which is awesome, but its also hard to troubleshoot magic.


#31

Do you remember if you were using the Digimesh protocol or one of the other methods?

I can see how sleeping nodes and using one of the other mesh topology options can make things more difficult.

I know @Rftop is successfuly deploying the 900mhz XBee radio networks in Digimesh mode that are bigger than 30 nodes with zero issues.


#32

I do not remember using DigiMesh in particular. I could dig it up in my old code if its really important to you, but I’m not sure I want to revisit all that. What I do remember is exhausting all options before having a few calls with Digi Technical Support / Sales and determining that DigiMesh was not going to be a good fit for our use case.

We wanted to push to 50-100 devices on a single mesh network – they said it was possible with extreme customization and planning on the network OR splitting the network up into multiple networks on different bands.

They could definitely have changed this limitation since I moved to Particle Electrons.

@Rftop – I’d be interested to know if you’ve had good experiences with large Digi mesh deployments. At some point I am sure we will cycle back to some sort of mesh, as we’d like to add wireless sensors to our primary product.


#33

Yea, the Digimesh scales better based on what I have read about different options.

I will soon be able to report back on larger sized network deployments in the 100 node quantity range using Digimesh on 900 MHz XBee radios.

I will be keeping network traffic to a minimum and all Nodes will be powered on via a AC wall adapter or built in rechargeable battery so no sleep modes to deal with which can makes things more difficult.


#34

That article is from 2009 – I’m sure I used Digimesh since I was prototyping my larger network in ~2014.

I think if you’re planning to power them all and keep network traffic low, you could be fine. I personally would not believe their claim of 500 devices on a network. I’d be interested to get the details on how they achieved that number and whether it is theoretical or tested and in what environment.


#35

The radios you have listed on EBay are obsolete now based on the product number.

The radios your selling look to be Zigbee Mesh Topology only so I doubt you ever tried Digimesh or the other Mesh topology that the other newer modules can work on.

The Zigbee MESH topoligy you were using is less than ideal compared to other options so that may be part of the reason it didn’t work out well for you.

Digimesh may be worth trying if your willing to give it another shot.

As far as max node size for Digimesh I think it’s 128 nodes max for always power nodes and more nodes if you devices are all just waking up and publishing data every now and then.

@Rftop will have more feedback on this.


#36

You are right, the S2B does not support Digimesh. Maybe if I’d used that it would have solved the issues with my deployment.


#37

I believe it’s 256 devices online per DigiMesh (900HP) Network, but there are ways around this.
{Edit} S3B hardware, not the S2B (2.4)


#38

@Rftop I got the 128 nodes from the Digi 900Mhz radio manual.

I did see in a link above it says you can do 500 nodes with Digimesh.

I’m not sure where the limitation comes from. Seems like it would be easy to setup two 128 node networks and have a single Photon be the Gateway for both networks.


#39

My guess is they will be happy to accept your money for their “optimization services” :wink:
For a very dense network, you can select the range of 64 channels to use, but most projects wouldn’t need to.
I just define a private network with the HP setting (Preamble ID).

For me, the limiting factor is the 1 publish per second limitation for the Particle Cloud/Gateway.
In a normal IoT scenario, the DigiMesh network is not the bottleneck. It will handle way more data than we should be pushing to the Cloud


#40

What is the max amount of nodes you have deployed at any single site?