Open Source Verilog tools for the Tang Nano

These amazing tools are part of the yowasp [https://yowasp.org] project that builds cross-platform tools based on YoSys [https://github.com/YosysHQ/].

INSTALL

The synthesis tools can all be installed through Python:

sudo pip3 install yowasp-yosys --upgrade
sudo pip3 install yowasp-nextpnr-gowin --upgrade

There is a script to do this

./INSTALL.sh

The final tool is openFPGALoader. It lives [https://github.com/trabucayre/openFPGALoader]. There is a script to build this

./install_openfpgaloader.sh

Alternately there is a Docker container that can do the same thing...

docker-compose up --build

Running the blinky example

Start with the following module which just flashes some LED's on the board. To make things simple, we have the file tangnano.cst that specifies the name and locations of pins on the tang nano. The relevant part describes the LEDs

module top (
    input clk,
    output [`LEDS_NR-1:0] led
);

reg [25:0] ctr_q;
wire [25:0] ctr_d;

// Sequential code (flip-flop)
always @(posedge clk)
    ctr_q <= ctr_d;

// Combinational code (boolean logic)
assign ctr_d = ctr_q + 1'b1;
assign led = ctr_q[25:25-`LEDS_NR];

endmodule

Download the pin descriptios

wget https://raw.githubusercontent.com/YosysHQ/apicula/master/examples/blinky.v
wget https://raw.githubusercontent.com/YosysHQ/apicula/master/examples/tangnano.cst

Using the Makefile

To just do the synthesis:

make blinky-tangnano.fs


make blinky-tangnano-prog

Requires openFPGALoader to be installed in /usr/local/bin/openFPGALoader. Alternatively, you can use the Dockerfile and docker-compose to program the FPGA

docker-compose up --build

Target the Tang Nano 4k

This uses a different device and pin number. Override these on the make command line

make DEVICE=GW1NSR-LV4CQN48PC7/I6 LED_PIN=8 blinky-tangnano-prog

Using the tools by themselves

Now synthesize the verilog, producing a blinky.json file:

yowasp-yosys -D LEDS_NR=3 -p "read_verilog blinky.v; synth_gowin -json blinky.json" blinky.v

The next step is to place and route the design onto the tang nano board.

yowasp-nextpnr-gowin --json blinky.json \
          --write pnrblinky.json \
          --device GW1NR-UV9QN881C6/I5 \
          --cst tangnano.cst

Then generate a programming file:

gowin_pack -d GW1NR-UV9QN881C6/I5 -o pack.fs pnrblinky.json

gowin_unpack -d GW1NR-UV9QN881C6/I5 -o unpack.v pack.fs

yosys -p "read_verilog -lib +/gowin/cells_sim.v; clean -purge; show" unpack.v

Finally program the device using openFPGALoader:

./usr/local/bin/openFPGALoader -b tangnano pack.fs