Tuesday, July 24, 2012

Project: OLS Logic Analyzer Hardwood Case

My Bus Pirate Case turned out so well that I decided to use the same approach to create a hardwood case for my Open Bench Logic Sniffer.

This is a open source logic analyzer with some pretty impressive specifications for the price.  It can handle sample speeds up to 200 million samples per second with up to 32 channels,  with varying numbers of samples based on the number of sampled channels, up to 16k samples for 8 channels.

16 of the channels are buffered 5 volt tolerant channels - these are the ones you see at the end of the board (and the only ones I've used so far).  There are another 16 channels (unbuffered 3.3v) on the unpopulated headers on the board.

I spent $50 for mine at Seeedstudios.

There are several software solutions available that talk to it - including the open source Java SUMP toolset that I have been using.  The hardware and software combination includes parallel and multi-step sequential triggering and adjustable pre-trigger storage.

Like the Bus Pirate, the OLS is a bare board, which puts it at risk of shorts from messy work surfaces with conductive things like paper clips and staples laying around.  I had previously hacked together a case from leftover acrylic and MDF, but this one is much better looking and more functional.

I did much of the work for this at Xerocraft -- our new Tucson hackerspace, using the milling machine to cut the openings in the chunk of leftover maple.

See the previous post on the Bus Pirate case for detail on the steps involved.

In short:

  • Cut an appropriate sized chuck of wood with a hand saw.
  • Milled the cavity and USB opening with the mill at 600RPM with a 1/2" end mill. 
  • Squared off the opening with a chisel and sander.
  • Rounded the corners and sanded a smooth shape with a belt sander.
  • Stained with the stuff I had lying around
  • Two coats of polyurethane with a light sanding between.
I again used #4 nylon machine screws and spacers to mount the board.  Because this board only has two mounting holes on one side, I added two extra holes on the other side evenly spaced such that one of then was directly below the buttons.  Nylon mounting parts are very reasonably priced in quantity, and are very easy to cut to exactly the desired size.

I marked the mounting holes with a transfer punch, then drilled and tapped the holes directly in the hardwood.  I screwed the machine screws in using the spacers and cut the excess length from the bottom with a good pair of flush cutters,  The screws with no hole got screwed in to the proper height to support the board from the bottom then cut off the same way.

I think it turned out pretty nice.

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