Douwe de Vries

Tang Nano 20K

—

by

douwe
in

Installation

The following applications are required:

  • yosys
  • nextpnr-himbaechel
  • gowin_pack
  • openFPGALoader

yosys and openfpgaloader

Install both yosys and openfpgaloader via apt.

apt install yosys openfpgaloader

https://github.com/yosyshq/yosys#setup

gowin_pack

Install via pip

pip install apycula

https://github.com/YosysHQ/apicula

It could be that the error “error: externally-managed-environment” occurs. This can be solved by adding the flag –break-system-packages to the install command.

nextpnr-himbaechel

This one is a bit more tricky as it needs to be compiled. For dependencies please see git repository: https://github.com/YosysHQ/nextpnr?tab=readme-ov-file#prerequisites.

git clone https://github.com/YosysHQ/nextpnr
cmake . -DARCH="himbaechel" -DHIMBAECHEL_GOWIN_DEVICES="all"
make -j$(nproc)
sudo make install

Usage

Now lets use the system we just installed. The code needed for this can be found in my git repository: https://github.com/douwedevries/tangnano20k. This includes sythesize.sh, tangnano20k.cst and topentity.v. They are all the files that are required.

sythesize.sh

This script first sets some variables to let the tools know we are working with a Tang Nano 20k. Next it goes though the tool chain. Each step should be confirmed with an enter. This allows you to read error messages. ctrl+c can be used to escape the script.

This file contains a simple verilog description that allow the leds to count when a button is pressed.

tangnano20k.cst

This file connects object name to object location. Or simply said, the verilog name to the actual hardware pin. Sipeed provides a file called Tang_Nano_20K_3921_Schematics.pdf in which the hardware is described. From you can create your custom CST file. The file in my repository only contains the system clock, leds and keys.