README.md

iCE40 Ring Test

Dependencies

• IceStorm tools
• yosys
• nextpnr

Install instructions for all of the above tools can be found on the IceStorm website.

Building

The default make target synthesizes the design and runs a timing analysis. The target prog programs an available iCEBreaker via USB.

Results

When clocking the FPGA at 24MHz, the resulting ring oscillation is still identifiable as a square wave.

By 111MHz, it's more of a triangle wave. But still stable and nearly rail to rail. This is the fastest clock speed that icetime approves.