JNZ testing and availability Dec 2016

At the time of writing this (end Dec 2016), there have been three prototyping rounds for the new JeeNode Zero. The current “rev3” board is getting close to the intended final release - the STM32L052 µC is a good choice, and due to STM’s impressive chip compatibility, the same PCB can be used with a variety of other lower-cost or higher-performance chips.

There’s an optional CR2032 coin cell holder on board, which sets the stage for a very small self-contained Wireless Sensor Node. The lifetime for autonomous use will depend entirely on how well the sleep mode is implemented (looking great so far), the sensor’s own quiescent current, and of course the duty-cycle requirements for radio use.

There have been some experiments with on-board sensors, but due to the huge range of available sensor types, the variety of expected use cases, and the relatively quick pace of innovation in that area, the JeeNode won’t be fitted directly with sensors on the board itself. Some novel ideas are being explored right now, but it’s too early to tell how they will turn out.

The current rev3 board has been tested as a “fridge node” at JeeLabs, i.e. placed inside the fridge, reporting temperature and humidity over wireless - and it was really surprising to see just how wide the temperature swings of a 20-year old unit were: over 5°C!

So what’s the next step?

There are four tasks ahead: 1) gaining more experience with these nodes, 2) finalising the board design, 3) building some test jigs, and 4) getting production and assembly runs going.

Several dozen rev3 boards have been assembled so far, loaded up with firmware, and verified to work - including this set of twenty sample units:

All units include a CR2032 coin cell battery holder (except that one in the front: we ran out of components during the last assembly run), since this will be a major use case for these nodes.

If you’re interested in this development, and would like to try them out and help come up with the final adjustments needed to make these maximally useful in a truly wide range of home monitoring + automation scenarios, you can now order one from the JeeLabs shop.

The price of the new JeeNode Zero will be identical to the classic JeeNode: €18.50, quantity 1. Due to the very limited availability of these initial boards, please order only a single unit.

The units in this first batch were all manually solder-pasted, picked-and-placed, reflowed using a neat vapour-phase reflow oven, flashed w/ Mecrisp Forth, and verified to receive RF.

To use the JeeNode Zero at this stage, you should be prepared to re-flash it with new firmware if important fixes or improvements are made in the next few weeks. For this, you will need to assemble a SerPlus using a Blue Pill or HyTiny board (or equivalent). Which in turn requires either an FTDI serial interface, a Black Magic Probe, or an ST-Link to upload the SerPlus code.

For wireless trials, to be described in an upcoming article, you’ll need another RFM69-based node to talk to, set to 868 MHz in “native” mode (the JNZ’s RF69 driver has no compatibility mode). A JeeNode v6 or JeeLink will be fine for this once you select the correct library that uses the “native” packet format.

While these requirements may seem daunting to some, please keep in mind that the current rev3 batch is really intended only for people who want to be actively involved in this phase of the process. Now is the time to push it in various new directions, and come up with ways to improve on the choices made so far. The more this design gets a beating now, the more useful and flexible it can be in the years ahead, as building block for numerous fun tasks in the house or local surrounds.

The first three revisions are a good example: components and connections have changed, a serious bug with serial-vs-untethered use has been found and fixed, and slightly adjusted pin choices for the main header have increased flexibility. But there might still be more tricks to increase the (re-) usability of GPIO pins or bugs lurking in deeply hidden places.

Although the Chinese New Year festivities may throw a spanner in the works, the plan is to have the JeeNode Zero in production by the end of Februrary 2017. Exciting times ahead!

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