Computing stuff tied to the physical world

Meet the JeeSMD kit

In AVR, Hardware on Mar 18, 2010 at 00:01

Meet the new kid kit in the Jee family – the JeeSMD !

DSC_1246.jpg

At a glance:

  • Same pinout as a JeeNode – same 4 port headers, same PWR/SER/I2C, same SPI/ISP
  • No wireless, no FTDI, just an ATmega328 – all SMD (32-TQFP, SOT-23, and 0603)
  • Two extra pins on the right side (allocated to the RFM12B module on JeeNodes)
  • Has a 3.3V regulator, a 16 MHz resonator, and four passive components

What’s the point? Well, it’s going to be made available as an SMD kit, and it’s going to be low-cost. If you don’t care about wireless or FTDI, then this is a convenient and compact way to hook up some Jee Labs plugs.

Of course, all the other stuff fits as before, including the Proto Board, for example:

DSC_1247.jpg

Here’s the board in more detail:

DSC_1243.jpg

(don’t look too closely at this prototype PCB – there are some silly cosmetic mistakes…)

There are some trade-offs w.r.t. JeeNodes:

  • No FTDI on board – you have to either add the equivalent connections yourself via the left and right headers plus a 0.1µF cap, or use ISP for flashing the ATmega328 chip
  • No wireless, so this isn’t a “node” in the usual sense – just a tiny Arduino’ish board
  • It’s all SMD, so if you want to practice soldering SMD by hand – this is one way to get started!

I’ve got a few boards for people who want to get their hands on them. The kits will be ready in about a week.

Now the JeeSMD kit needs a detailed set of instructions and close-up shots on how to assemble and start using it – more work to do!

  1. To reduce the height clearance, you could use machined (round) headers. I found them much better even from the electrical (contact) standpoint. See my post here: http://timewitharduino.blogspot.com/2010/01/what-difference.html.

    • Good point. Or forego the headers altogether. I agree that with something as small as this, headers are starting to take up a relatively large amount of space/height. For me, the main use will be “deeply embedded” (and permanent), maybe even soldering some plugs directly to the ports with short pieces of wire. Without headers, you can builds some pretty flat (or tightly-sandwiched) units.

      That’s also why I’m considering including only the PWR/SER/I2C and ISP/SPI headers in the kit.Enough to get going, but leaving all the options open w.r.t. the port headers.

  2. It will probably never be an issue but at 16MHz and 3.3V you are overclocking the MCU according to the datasheet (see the Speed Grades section in DC characteristics).

    • Yes – I’m aware of that – http://news.jeelabs.org/2009/02/27/out-of-spec/

      So far, I haven’t ever seen it cause problems – as you point out. I don’t know whether the clock itself is an issue, or circuits further down the line. In the latter case, one could run the units at a lower frequency using the system clock pre-scaler, e.g. when used in a wider temperature range.

  3. Whoops must have missed that… Thought I had read most of the blog posts. Following this project with interest. Great work!

  4. Sorry, most of (me) us cant do SMD soldering.

    I could solder the headers on, and that is one great Arduino (ish) kit in my opinion.

    but I dont have SMD soldering sorted.

  5. my point is I think this thing is actually Revolutionary when combined with the Ports library and Plugs.

    But I cant build one to save my life.

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