Using More Than One Gateway/RFM69 Network

[papa]

In the thread, Star vs mesh topology, Jan 5, 2016 13:20:35 GMT -5 computourist said:
Hi gandalph ,

Interesting idea, but also very complex. Every node would need some routing mechanisme, duplicate message prevention, maybe queueing and a lot more.
It would be good to first think on the functionality you would want; all cpu-power and memory needed for the mesh network functions would be lost to end node -sensor- functions. Given the limited resources of the Arduino chip this is a serious limitation.

Another option to consider would be using multiple gateways. This leads to a multiple-star topology. The gateway acts as a standard MQTT client to the broker and nothing keeps you from connecting multiple gateways. Each gateway could have a separate network number. The topic naming scheme used allows the root of the MQTT-topic to be different for each gateway (i.e. /home/rfm_gwA, /home/rfm_gwB, etc). The MQTT-broker would deliver all messages to the proper Openhab destination.

This setup would be static (not dynamically adjusting to circumstances like a mesh network) but for the majority of purposes it would be adequate.
It sure is a lot easier to implement

A last option would be to use multiple gateways within the same radio network. If the link to an end node is lost another gateway would take over.
For transmission to the node Openhab could decide which gateway to use, based on error messages received. Reception of end node messages would mostty be in multiples. With proper programming Openhab should be able to cope with that..... This setup is dynamic in nature and has the benefit that no extra code is needed on the end nodes.

In that thread, I agreed that more than one gateway/RFM69 Network seemed like the most doable way to spread the communication load & expand the capability of this project.

However, I did not try to create more than one gateway & network until lately.  I must admit that I stumbled around a bit with it, not knowing much about Mosquitto (MQTT).  My struggle & how I finally got the last piece is documented here.

In this thread, I'll try to document the essentials of having more than one gateway & nework.

[papa]

This will work for networks built around a computourist Gateway version 2.3 - 2.5.  At any one time, I have 2 or networks happily connecting at the same time to MQTT & OpenHAB UI.

Of course, you need to have built the gateways of either version & at least one node per gateway. To do this, see this thread & the other threads linked in that thread.

The first Gateway & node network you can pretty much use the sketches & OpenHAB items as described in that thread.

    For the second network, make the following changes in the Gateway Sketch & OpenHAB items.
[Not all these changes may be absolutely required, but making them will probably help keep each network's communications separate & not interfering with each other. One of them can help you keep straight which network a node is with.]

    In the section that starts with "// Ethernet settings"
1) Create a NEW MAC address by changing the last set of characters that starts 0x
       Be sure the MAC address is different from every other device on your Ethernet network.
2) Create a new Gateway IP address (if DHCP fails)
3) KEEP the mqtt_server mqtt broker address the SAME as the first Gateway.

                    In the section that starts with "// Wireless settings"
        [Even though it says keep NODEID as 1 ... ]
1) Change the NODEID to some UNIQUE number within your whole project (I used 250 for my second gateway)
2) Change the NETWORKID to some UNIQUE number within your whole project (I used 200 for my second gateway & would use 300 for the third)
3) Change the ENCRYPTKEY to be different from the first gateway & use this ENCRYPTKEY with all nodes to be connected to this gateway.

    Several places in the Gateway Sketch have the MQTT topic start "home/rfm_gw"   stricken text is not needed
For the second Gateway, I changed all these places to start with "hom2/rfm_gw" (For Gateway #3, I'd use "hom3/rfm_gw".)

Find the sketch line with "rfm_gw/nb/node01"  << At the end of that phrase, change node01 to the NODEID you used above, like node250.

    See the pattern which helps to show which network the Gateway & the node are in.
I recommend a small label on each gateway & node, indicating its version, NODEID, & NETWORK.

In OpenHAB's items file, to subscribe to messages from a node in the second gateway's network, still use home/rfm_gw

        Very important that hung me up a while:
For the second Gateway, find the line *clientName = "RFM_gateway"; & change it to *clientName = "RFM_gatewy2";
     For the third Gateway, I would change it to *clientName = "RFM_gatewy3";

                In a sketch program for a NODE to be connected wirelessly to the second gateway...
        set the following to match what's in the second gateway's sketch:
1) ENCRYPTKEY
2) NETWORKID
3) GATEWAYID  (Use the number assigned to NODEID in the gateway sketch.)

I believe that's all it takes to create two networks connected to the same MQTT server & OpenHAB UI.  It should provide a model that will spread the communication load & extend the capability of this DIY Home Automation project.

Update, Dec. 16, 2018: See this post for links to sketches that add the option of multiple RFM69 gateways / networks.