Tuesday, June 19, 2012

JeeNode Review

I've been playing around with JeeNodes lately and I thought I'd post a review.

Executive Summary
I really, really like JeeNodes.  The software APIs are easy to use and intuitive.  Soldering them was easy.  The PCBs are well thought-out.  My main complaint is the documentation.  It's not that the documentation doesn't exist or that it is unclear.  The problem is the documentation is badly organized and hard to find.  I will attempt to organize the documentation I used in this posting.

JeeNode v6 intro
I've been interested in doing some home automation projects and was looking for a good solution for smart wireless nodes.  I looked into the typcial XBee plus Arduino solution that lots of people used but I want to have many nodes and at $40-50 per node XBees were too expensive.  Then I found JeeNodes which can be summarized as inexpensive Arduinos with 2-way radios.  I purchased a set of 3 JeeNodes plus a USB-BUB from Modern Device.  The USB-BUB is a little USB adapter used to program a JeeNode.  It's only needed during programming so I bought one.

JeeNode assembly
I largely followed the instructions from the site above.  The only major difference I found was that the large electrolytic cap provided with the kit was much taller than the one in the instructions so I would recommend leaving it for last. This component is the tallest thing on the board and it's easiest to solder the components from shortest to tallest.  For the right angle header on the end, it's a little different than the instructions which use a straight header; it's actually easier.  Just solder one pin then re-flow the solder as needed
to get it positioned properly, then solder the rest of the pins.

Initial Tests
JeeNode initial tests
As far as power settings: The Vout jumper on the USB-BUB should be set to 5V while the LGLV should be set to 3.3V (or VL).  The 5V will power the Jeenode and run through the onboard 3.3V regulator, while the 3.3V will be used for logic levels.

Software setup: Download arduino IDE from here.  Download and install JeeLib library from here using instructions in readme.

Next follow the instructions for the RF12demo sketch which should be located here: \libraries\JeeLib\examples\RF12\RF12demo\README

Luckily the RF12demo app is already flashed into the JeeNodes so you can skip that step.  I kept one JeeNode attached to the USB-BUB for communication and the other one I stuck into a breadboard and powered with 5 volts via the programming header pins marked VCC and GND. Worked like a charm.

Sending packets via the RF12demo sketch is described in stesp 9 and 10 of the README.

The RF12demo (the sketch that the JeeNodes come preprogrammed with) displays received messages like this:

"OK 2 122 3"

which is interpreted like this:
"OK" = checksum passed ("?" means checksum didn't pass)
"2" = node id
"122 3 ..." = data payload

Reference Material
JeeNode v6 schematics and user manual
JeeNode power tips

I'm amazed at the quality of the end device.  The silkscreens are very good to the point where you really don't need assembly instructions.  Also the little things like the fact that the battery leads have built in strain relief through the PCB, and the port headers use the Sparkfun-style staggered holes to hold them in place
while soldering.  The software is easy to use especially once you've pinpointed some of the useful examples sketches from the JeeLib directory. The only thing that has been annoying is that the proper voltage settings for the USB-BUB are not spelled out; I had to look at the schematics for both the USB-BUB and JeeNode to figure out
the proper settings.  And as mentioned before generally the documentation is spread out willy-nilly across the jeelabs site.

Further Reading
The following examples are handy to use as building blocks for later reading.  I would also suggest perusing JC's blog and reading his various articles, he really goes in depth on various topics especially power management, which is very enlightening.

There are some very helpful and knowledgeable folks on the JeeLabs forums.

Here are some useful examples (from the the /libraries/JeeLib/examples/RF12 directory):
  • rfRangeTX - good example of a simple transmit
  • radioBlip - good example of putting processor and radio to sleep and waking up and sending message
  • roomNode - complex example of a full sensor node implementation