Computing stuff tied to the physical world

More JeeNode v3 changes

In Hardware, News on Jun 22, 2009 at 00:01

Here are a few more details about the upcoming JeeNode v3 board.

First off, I said no more changes w.r.t. the pinout. Not true – the I2C/PWR pinout has also changed:

i2c.png

For a couple of reasons which I don’t want to go into just yet. The GND pin is now on the outside, just as on the FTDI header. Note that PWR is the incoming voltage, not the regulated 3.3V at which the ATmega operates (including those SDA / SCL pins).

The other change worth mentioning here, is that components have been rearranged slightly to make room for 2 pads to connect a battery or battery pack – along with holes for strain relief. Both leads are clearly marked “+” and “-” to avoid polarity mistakes.

The JeeNode is well suited for battery use due to it’s 3.3V design and because it has no on-board LEDs. The regulator lets you choose from a huge range of battery options (hence the soldering pads i.s.o. a fixed battery choice): 3x or 4x AAA or AA, NiMH or Alkaline, or one of the increasingly popular 3.6 .. 4.1 V Lithium batteries, which are great as long as you take care not to short-circuit them and not to discharge them beyond their advised limits.

So there you have it. The new JeeNode v3 board is just about ready to send off to manufacturing. I hope to get my hands on them early July.

  1. Just a note on your i2c pinout: The i2c specification recommends the following wiring pattern for i2c cables: SDA-VCC-GND-SCL This is to reduce the coupling between the data lines to minimize cross-talk over large (>10 cm) distances.

    Most i2c pinouts I’ve seen violate this though, so there doesn’t appear to be a de-facto standard for this apart from the specification recommendation.

  2. Thanks. Yes, I2C pinouts are all over the map from everything I’ve looked at. In this case there is an argument to be made to not match the recommended pinout, because it’s not VCC but the higher PWR voltage on one of the pins. For longer range use, I hope that it can be addressed with an example one day, on this weblog or elsewhere – showing how to get the max out of the I2C hardware.

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