nanode serial bus

[Andrew Elwell]

Hi Folks,

I'm at the stage of needing another arduino style atmega and am trying
to decide between another nanode or going for a freetronics etherten
(here in .au they work out roughly the same after shipping - I can
pick up an etherten in the local jaycar brick n mortar store.

One reason for perhaps sticking to the nanode is to use the
inter-nanode serial bus -- what's the state of this? did it ever get
developed into something useful?

My use case is to have several nanode style boxes with sensors /
contacts off them around the property. Given that they will all
eventually post back to an internal guruplug head the simple way is to
use ethernet but running long range serial may be quicker in short
term till the remote corners of the place are networked.

Advice?

Andrew

[Nicholas Humfrey]

Hello Andrew,

Creating a serial bus between multiple small devices is something that I am very interested in too.

I have been looking at doing MQTT-S over a multi-master half-duplex RS-485 bus - maybe I just like being punished? The reason for the multi-master is so that light switches can initiate communication and reduce the latency of switching on a light. Collision detection is likely to be tricky though. The electronics to do half-duplex (single balanced pair of wires) RS-485 looks fairly straight forward.

As far as I can tell the Nanode implementation is pretty basic. Most of the complexity would be in the firmware. The nanode is full duplex, which probably implies that it has to be used in a master-slave setup. Perhaps you could ask the Open Energy Monitor guys and see how far they got with it? Biggest blocker to using Nanode is probably finding someone to sell you one.

However, if having a single master and multiple slaves is good enough for you, then why not use a 1-wire bus instead? Then you can connect sensors, relays and many other devices with minimum number of components.

So I guess it depends when you want each of the nodes to do but I would use a Raspberry Pi for the Ethernet gateway node.


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[Andrew Elwell]

> I have been looking at doing MQTT-S over a multi-master half-duplex RS-485 bus

I have a feeling Andrew Beck of (possibly) this parish may have a club
for you to join :-)

> Perhaps you could ask the Open Energy Monitor guys and see how far they got with it?

Ah OK - I thought it was london hackspace who were the principal
proponents of it - OK I'll see what else I can dig up

> Biggest blocker to using Nanode is probably finding someone to sell you one.

Ah OK - is Debbie no longer running the store now ken's off to
pastures/engines new?

> However, if having a single master and multiple slaves is good enough for you, then why not use a 1-wire bus instead?

Yeah - I'm already hoping to do this for temp sensors etc - I wanted
the 'comms bus' for sending status of other things - reed switches
etc.

I think I'm going to go overboard on the comms side though and put in
a breadboarded atmega directly into an old wrt54g (1.1) and/or my old
fonera 2100 - both of which have 3.3v and serial headers easily
accessible


Andrew