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• Tested. Works.

  Ted Yapo • 03/10/2018 at 23:31 • 0 comments

  The PCBs arrived last night, but I had to wait for this morning for the box of parts from DigiKey - I almost got the timing right this time.  Here's the assembled board with a Roman denarius for scale.  It's pretty small.  The #TinyFPGA Programmer is plugged in on top.  It programs the FPGA just fine.
  

  I was careful to apply just a little paste with a 25 Ga needle since I've been having issues with QFN packages. I still got 3 solder bridges I had to clean up with an iron, but otherwise it worked OK.  I think my paste is getting old - it's probably two years old now and never been in the fridge (I can hear you cringing, people :-)

  I wrote some quick test verilog just to make sure all the pins work, and they do.

  Now, I can build a few more of these things and put them to use.

  I think I'm going to make a composite video frame grabber as a test.
  

• PCB: First Cut

  Ted Yapo • 03/01/2018 at 03:09 • 0 comments

  So, I threw together a quick breakout PCB for the MachXO2-1200 FPGA. The idea is that you mount it to a solid ground plane (un-etched copper clad) by soldering down the castellations on the edges, then connect it up with wire wrap (twisted pairs when needed).

  The bottom has no soldermask, so it can make good contact with the ground plane.  You could theoretically reflow it to the plane, but if you just tack-solder the 6 castellations, you could remove the PCB if desired.

  The circuit is pretty simple: FPGA, bypass caps, and a 4k7 pulldown on the JTAG clock line I shamelessly stole from the TinyFPGA design.  It presumably keeps the clock from toggling spontaneously and screwing things up. It's mostly solder pads, really.  I added s 5-pin surface-mount header that's compatible with the TinyFPGA programmer.
  

  
  I've sent design to OSH Park, and now just have to wait.

  In case anyone is wondering what this is all about, here's another project I made with similar boards:

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