I just got a blinky project working for my new ULX3S Board with a 45F FPGA chip. I had to git clone and rebuild all three of yosys, trellis and nextpnr. Details of doing this are at https://github.com/YosysHQ/yosys and https://github.com/YosysHQ/nextpnr#nextpnr-ecp5 . I used git repos of the above dated early December 2018. The early November 2018 ones didn't work.

The version of nextpnr I'm using supports an external constraints file. I have a v3.0.3 ULX3S board, and the constraints file for this is ulx3s_v20.lpf.

The blinky.v file can be simulated under Verilator, just type make at the command line. It will use blinky_tb.cpp as the testbench and that requires testb.h.

To build the ULX3S bitstream, do a make ulx3s.bit . If you don't have a 45F FPGA chip, change the nextpnr-ecp5 --45k line in the Makefile to something more suitable. If you have an older board, you will need to find a constraints file that matches your board. Have a look in https://github.com/emard/ulx3s/tree/master/doc/constraints .

Making the ulx3s.bit file requires blinky.ys which tells yosys what to do, and ulx3s_v20.lpf and ulx3s_empty.config to tell nextpnr what to do.

Use ujprog from [https://github.com/emard/ulx3s-bin] to program your board.

If you are using the serial link to the FT231X chip, you need to disable hardware flow control. With minicom, ctrl-A O, Serial port setup, F, Exit.

As I get other projects to work on the board, I'll put links below:

• Echo characters on the USB serial port
• Tic Tac Toe using the serial port, and with HDMI output
• A 4-bit CPU using the serial port
• A HDMI test pattern generator based on Emard and Dan Gisselquist's code