Computing stuff tied to the physical world

Programming the JNµ v3 – part 1

In AVR, Hardware on Mar 3, 2013 at 00:01

The new JeeNode Micro v3 announced yesterday does some very subtle things w.r.t. how it deals with the SPI bus during ISP programming (don’t you love those silly acronyms?). I’ll have a lot more to tell about this in a future weblog post, but for now let’s just focus on getting a new sketch into the ATtiny84 chip!

As mentioned yesterday, there is no longer a standard 2×3 ISP header on this board. It’s just a 4-pin header, with GND and VCC obtained from the 8-pin header on the side of the board. For reference, here is the ISP header pinout as most ISP programmers expect it:

ISP 6 way pinout

In my case, I wanted to use the modified AVRISP mkII programmer, so I’ve set up a little cable + breadboard hack, as follows:


The 2×3 to 6-pin (actually 5-pin) header was constructed from an Extension Cable. Here is the hookup, using 2×3 long header pins to connect the 2 female ends together:


And here’s the breadboard side of things, in close-up:


Note the sixth wire (providing or sensing VCC power), which goes to either +3V or PWR on the main header. This flexibility will in fact turn out to be quite convenient when dealing with direct-power vs boost-power versions of the JeeNode Micro.

So much for the hardware side of things. The software side turned out to be a lot trickier, and I’d like to take a little more time to work out the best way to do things. After a short intermezzo tomorrow, will come part 2 – stay tuned!

  1. Well, it’s a lot of wire twisting this. Inventing of a new connector to gain (or loose) a few square millimeters on the board. I would have kept the standard ISP connector.

    • For a single unit, I’d agree – but I intend to sprinkle lots of these around in various projects, and for me size is currently more important than the one-off ISP adapter. For more standard stuff, I use the regular JeeNodes.

  2. How about designing the board to take the ISP 2×3 pin header to feed both sides at the end. A 2×3 pin male could slide on the end, making contact at 3 points on both sides. After programming is done, slide it off and you have a much shorter device. If you wanted it to stay on the micro, it could still be soldered.

    • Yep, it’s definitely an option. It’s on the list of things to reconsider for a future revision.

  3. @Ratib, nice idea. Not quite compatible with the board thickness, but with a little mechanical adjustment could work for the “slide on” case.

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