[TriEmbed] ChainDuino (on Kickstater)

[The MacDougals]

I have been working on RS485 network of Arduinos for my home automation
projects (cat feeder, drip irrigation, rain gauge, temp monitor, ...)
I am using an ATTiny84 and a MAX3483 chip and running RJ12 (4 conductor)
wire between them (daisy chain, not star).
The MAX3483 chip only does half duplex, so the 4 wires are a differential
pair, power, and ground.
Using Cat5 cable, I could see using power, ground, A/B outgoing and A/B
incoming (with 2 wires unused) to emulate a star topology.
You would need a central "hub" to handle the proper connections and power
amongst the cables.

I have not been terminating my cable runs with the 120 ohm resistors.
Things were not working with them on and did work fine without them.
I have not gone back to retest with proper termination.  I am only running
at 9600 baud, which I was told could be a reason it works w/o the
termination.
I currently start at a Raspberry Pi, run 50 feet to the drip irrigation node
and then another 35 feet to the cat feeder.
I am pulling power off of the Pi (3.3v).  With nothing going on, the current
is about 14mA to power the two remote nodes.

I am posting results from the rain gauge to Sparkfun.  I will show that at
the next meeting.

I plan to document this project better on the website in the near future.  I
can make the PC board for my design available on OSH Park if there is
interest.

---> Paul


-----Original Message-----
From: TriEmbed [mailto:triembed-bounces at triembed.org] On Behalf Of Bill
Farrow
Sent: Friday, August 22, 2014 4:19 PM
To: Rodney Radford
Cc: TriEmbed Discussion
Subject: Re: [TriEmbed] ChainDuino (on Kickstater)

On Fri, Aug 22, 2014 at 3:29 PM, Rodney Radford <ncgadgetry at gmail.com>
wrote:
> Very nice, but I am a little confused on the connection topology.  
> This device shows 2 ethernet jacks where the boards are connected in 
> series (A -> B -> C -> D...) which would be very limiting when it 
> comes to running boards around the house.  They also mention a 6 pin 
> header and a 6 wire IDC option on board.

The idea is to daisy-chain them using the RJ45 sockets using off the shelf
CAT5 cables. This would work quite nicely if you wanted to wire a greenhouse
or a perimeter fence.

The 6 pin connector is so you can use a continuous run of CAT5 cable to
connect multiple devices by crimping an IDC header onto the CAT5 wires
inline for each device.

You are correct: if you already have CAT5 wiring in your house, it is most
likely in a star topology, and I'm not sure that you could make this work
considering the RS485 termination requirements.

Bill

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