Attendees of the West Coast Propeller were offered the newest Schmartboard development board, the Parallax Propeller Schmart Module.  After the expo, I raced home to put it together, here's what I thought:

Packaging

While the label instructs the builder to check Parallax's site for more information, it's not yet available.  You can pick up the board today from Schmartboard, but it looks like the Parallax kit (which comes with the board, Prop, EEPROM and components) hasn't been officially released.  I can't evaluate the documentation that Parallax will provide, but I suspect it will be similar to other Parallax products: very good.  The kit comes in an anti-static bag, when you dump it out, you'll find the surface mount parts conveniently packed in a separate bag so you don't lose them.

The board is very small - 2" x 2".  Here's a photo for size comparison.

And here's a photo of all the parts in the kit.

Surface mount and through hole versions of all the passives are provided.  I found this to be extremely helpful, as a few surface mount resistors fell on my carpet & were never found again.  A 5MHz crystal is packed in, and so are 4 rubber feet.

Assembly was straightforward, even without Parallax's documentation.  I just grabbed the schematic from Schmartboard's product page and started soldering.  I couldn't see any value markings on the surface mount passives (there are 2 cap values on the board and 2 resistor values), but they're cut from their reel, so a little deduction makes it easy to figure out (the two identical resistors are 10k, the three identical caps are 10uf).

Soldering passives is a pain.  The problem is heating up the pad sufficiently without moving the component.  I got better as I went along, but it's not as easy as soldering through hole resistors and caps.  As noted earlier, the board has surface mount pads and corresponding through hole pads, and the kit includes both versions so the builder is free to choose.

Soldering the QFP prop is very easy.  Start by positioning the Prop exactly where you want it, the extended traces have extra solder, so you just push the iron up the trace to the IC.  I was able to quickly solder the chip on.  As I pushed the solder up, I did bridge a few of the IC legs, though.  I think most users will make a few bridges - they're easy to spot and easy to fix, as long as you have a solder sucker handy.  My soldering station is a low-end Elenco I got for $40 and has a standard tip – a smaller tip would have made the job easier.

Here's the result:

I switched the red LED with a blue LED from our inventory to make it look cooler.  I used a bit of my own solder and it has a ton of rosin, so there's a little extra gunk on the board (that can be removed with a dip in nail polish remover).  Build time was about 45 minutes.

Complaints — The pin sockets are set so it's not practical to plug the module into a breadboard.  Also, the sockets aren't labeled with their corresponding pins: you'll have to go back to the schematic (or whatever documentation Parallax provides) to figure out which socket is connected to which pin.

Nice Stuff — Including through hole AND surface mount components is a very nice touch.  The board also has a 5V regulator and pins for 5V out. Soldering QFP is easy with the SchmartBoard design.  Each set of jumpers has ground and 3.3V out.  I don't know what the price for the Parallax kit will be, but getting the board (plus a few extras) from Schmartboard is a reasonable $15. 

VERDICT
The Prop is available as a DIP package, so SMD soldering isn’t required to build a Propeller-based project.  But this board has a nice, small footprint and it’s well thought out and easy to put together. 


Great If — You're doing low volume Propeller prototyping.  You've already got a Prop Plug and experience with the Propeller.  You need a space-saving module.

Buy The Board From SchmartBoard »

Comments (5)

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Vaati

June 30, 2009

65.185.162.206

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Very nice!

Oh wow! That is very very nice! The thing about the QFN/P packages is that they are a LOT smaller than the 40 pin dip chip, which makes them perfect for smaller scale designs. I personally would probably prefer the ittybitty 1x1 propmod, as it has all the necessary stuff in an incredibly small space....

Nick

July 01, 2009

205.180.14.240

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Great QFP practice

One thing you can't beat about the Propmod is that you can use it with any project you publish. It's not a cheap part, but you can use it. The propmod is also pre-made, so you can just pop in and go. I think the Schmartmodule is more for folks who want to do some soldering and would just enjoy putting the thing together.

Michael M. Butler

July 03, 2009

75.30.177.102

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Tip(s) for holding down SMDs

Thanks for the speedy review!

One trick I use for non-critical parts is a tiny tiny dab of regular white glue (PVA) to hold them to their location while I solder. It seems to work fine, although I don't know if there are subtle side effects, so I try to stay away from that technique for low-level, high voltage or high speed circuit parts as much as possible.

There's another trick of using a semicircle of music wire stuck in a wooden or particle board base to make up a spring clamp to hold parts down, but passives are so small that's kind of not a good idea (heat sink!). Works great for chips, though.

Jim Gamblain

May 01, 2012

199.89.63.132

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Soldering tips

I read in your review about soldering passives being difficult, and I wanted to share my methods since I have been soldering for a good number of years, and have picked up a few tricks here and there.

What I do is put a very small amount of solder on one of the surface mount pads. Then, using a pair of tweezers, I line the part up with the pad and re-heat it, keeping the part centered and pushing downward slightly so the part becomes flush with the board. Once I am satisfied with the placement, I remove the iron, holding the part until the solder is cooled. Once that is done, I simply solder the other side of the part, and move on to the next component. For me, this method keeps everything nice and lined up, and is pretty quick. If one is worried about speed and lean manufacturing techniques, just prep one pad for each component, then place all of them like I just stated. Once all of the parts are "Pre-Soldered", then go back and do all the rest of the pads.

Jim Gamblain

May 01, 2012

199.89.63.132

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One more thing....

One more thing is I strongly urge against "a dip in nail polish remover". I have never tried it, but I would honestly be afraid that the plastic wrappings around capacitors would melt away, leaving you with at best a non-functioning board, worse case scenario, acid from them leaking out doing even more damage. I recommend as pure of isopropyl as you can find and a toothbrush or a hog's hair brush.

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