BeagleWire by Michael Welling is a fully open ICE40 FPGA BeagleBone cape:

BeagleWire: fully open ICE40 FPGA BeagleBone cape

BeagleWire is a completely open source FPGA development board. Unlike most other FPGA dev boards, the BeagleWire’s hardware, software, and FPGA toolchain are completely open source.  The BeagleWire is a Beaglebone compatible cape leveraging the Lattice iCE40HX FPGA.

BeagleWire can be easily expanded by adding additional external modules for example, modules for high speed data acquisition, software defined radio, and advanced control applications. Using well-known connectors like Pmod and Grove makes it possible to connect various interesting external modules widely available in stores. Owing to this, prototyping new imaginative digital designs is easier.