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FPGA STUFF

This page is about my interest in FPGA design. It is sooo much fun!

2026-06-13: FPGA design on OpenBSD 7.9

Ever wanted to design FPGAs whilst running OpenBSD 7.9? Now you can! I have recently purchased an Olimex GateMateA1-EVB.
It was rather reasonably priced, and the required toolchain was compiling with little modification on my OpenBSD machine. With a little bit of luck, when you are reading this, you might be able to install them by typing in

pkg_add prjpeppercorn nextpnr openfpgaloader yosys-takeover

Hello World example

A total of four files are needed:
- olimex_gatematea1-evb_cc.ccf for the input/output connection.
- helloworld.v for the actual design.
- 1_synth.sh to synthesize the bitstream.
- 2_program.sh to program the board with the bitstream.

olimex_gatematea1-evb_c.ccf

Net "clk" Loc = "IO_SB_A8" | SCHMITT_TRIGGER=true;
Net "btn" Loc = "IO_SB_B7";
Net "led" Loc = "IO_SB_B6"; # Led D1

Closer inspection of the board schematic reveals, that the main clock is connected to pin IO_SB_A8. And a LED to pin IO_SB_B6.
The intended way to give those pins names, which can be used in designs, is to place them in a .ccf file.

helloworld.v

module top(
        input  clk,		// connected to pin IO_SB_A8
        output wire led		// connected to pin IO_SB_B6
);
        reg   [23:0] counter=0;
        always @(posedge clk)
        begin
                counter<=counter+1;
        end
        assign  led=counter[23];
endmodule

This verilog file is a toplevel. Its input and output are directly connected to the pins via the names clk and led.

1_synth.sh

#!/bin/sh
echo "running yosys..."
yosys -p "read_verilog helloworld.v ; synth_gatemate -top top -luttree -nomx8 ; write_json helloworld_netlist.json ; write_verilog helloworld_netlist.v"

echo "running nextpnr..."
nextpnr-himbaechel --device=CCGM1A1 --json helloworld_netlist.json -o ccf=olimex_gatematea1-evb_c.ccf -o out=helloworld_bitstream.txt --router router2

echo "running gmpack (from prjpeppercorn)..."
gmpack helloworld_bitstream.txt helloworld.bit

This shell script synthesizes the bitstream.

2_program.sh

#!/bin/sh
doas openFPGALoader --index-chain 0 --cable dirtyJtag helloworld.bit

This shell script programs the FPGA board. If all went well, the LED on the board should blink at a leisurely pace.