Thursday, March 24, 2016

A bigger, almost as cheap FPGA experimenter's board

When I started looking at inexpensive FPGAs reference boards a few years back one I considered was the Lattice Semiconductor iCE40-HX1K. My Verilog i4004 implementation consumes 42% of the logic cells (and more than 58% of the 1280 PLBs). I expect I could probably squeeze the emulation for a few other MCS-4 chips needed for a simple system into it, but there wouldn't be a lot of resources left for anything else. Routing in an FPGA starts to become the limiting factor at some point even when there are free logic cells (75% seems to be a commonly quoted number).

The same line of Lattice chips has 4K and 8K parts. The 4K part comes in a 144-lead TQFP with 0.5mm lead pitch, which is manageable, but the 8K only comes in BGA packages. At the time there were no reference boards for these but that's changed; there is now a breakout board for the iCE40-HX8K:

This breakout board costs only $43 makes 120 I/Os available to the experimenter.

If the 1K part and only a few I/Os suits your needs, the iCEblink board seems to have been supplanted by the iCEstick, which is not much bigger than a large memory stick. It's dirt cheap at $22.

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