bronzebeard 0.0.9

Minimal ecosystem for bare-metal RISC-V development

bronzebeard

Minimal ecosystem for bare-metal RISC-V development

What

Bronzebeard is a collection of tools for writing RISC-V assembly and working with hobbyist development devices. It is designed for programs that will run on bare metal with no reliance on operating systems, frameworks, SDKs, or pre-existing software of any kind. The assembler currently supports RV32IM (AC are coming soon).

Why

Much of modern software has accrued vast amounts of bulk and complexity throughout the years. Can useful software be developed without relying on any of it? That's the question that this project seeks to answer. I believe that the rise of RISC-V provides a great opportunity to explore different methods of program development. Installing a full operating system doesn't have to be a prerequisite to building something useful.

How

Bronzebeard and its tools are implemented purely in Python. A simple, standalone assembler is the centerpiece. It has been written in order to be free from large, complex toolchains. This keeps the project portable, minimal, and easy to understand. At the moment, Bronzebeard only targets the Longan Nano and the Wio Lite. However, there are plans to broaden support to also include HiFive1 Rev B.

Documentation

Most of the surface-level documentation for Bronzebeard lives right here in this README. For more specific details regarding the usage and accepted syntax of the assembler, check out the docs directory. This is where the project's primary documentation will live until the time comes to setup something more official.

Installation

If you are unfamiliar with virtual environments, I suggest taking a brief moment to learn about them and set one up. The Python docs provide a great tutorial for getting started with virtual environments and packages.

Bronzebeard can be installed via pip:

pip install bronzebeard

Setup

All major operating system platforms are supported: Windows, macOS, and Linux. In order to utilize Bronzebeard, you need to download and install a recent version of Python. For more info, Real Python has a great installation and setup guide that I recommend following.

Windows

The USB-based devices that Bronzebeard targets don't work well with Windows by default. They each need to be associated with the generic WinUSB driver in order to be identified and programmed. The easiest way to accomplish this is with a tool called Zadig. With the device attached to your computer (and in DFU mode, if applicable), use Zadig to assign the WinUSB driver to the device. Note that you will have to apply this driver assignment to each physical USB port that you want to use for programming the device.

macOS

The only extra requirement on macOS is libusb. It can be easily installed via homebrew.

brew install libusb

Linux

Programming devices over DFU requires libusb version 1.0 or greater. The following command will install the library on Debian-based Linux systems such as Debian, Ubuntu, Linux Mint, and Pop!_OS.

sudo apt install libusb-1.0-0-dev

For other Linux ecosystems, consult their respective package repositories.

If you'd like to program and interact with the device as a normal, non-root user, create the following udev rules file:

# /etc/udev/rules.d/99-bronzebeard.rules

# Longan Nano / Wio Lite
ATTRS{idVendor}=="28e9", ATTRS{idProduct}=="0189", MODE="0666"
# Adafruit USB to TTL Serial Cable
ATTRS{idVendor}=="10c4", ATTRS{idProduct}=="ea60", MODE="0666"
# SparkFun USB to TTL Serial Cable
ATTRS{idVendor}=="0403", ATTRS{idProduct}=="6001", MODE="0666"

After the rules file is setup, reload udev via sudo udevadm control --reload.

Longan Nano

This section details how to run programs on the Longan Nano.

Cables

1. Attach the USB to USB-C cable for programming via DFU
2. (Optional) Attach the USB to TTL Serial cable (adafruit, sparkfun)
   • Attach GND to GND
   • Attach TX to RX
   • Attach RX to TX
   • Don't attach VCC (or jump to the 5V input if you want power via this cable)

Assemble

With Bronzebeard installed:

python3 -m bronzebeard.asm examples/led.asm led.bin

Program

Enable DFU mode on the Longan Nano: press BOOT, press RESET, release RESET, release BOOT.

python3 -m bronzebeard.dfu 28e9:0189 led.bin

After programming, press and release RESET in order to put the device back into normal mode.

Interact

If you have flashed a program that includes serial interaction, We can use pySerial's built-in terminal to communiate with the device.

To get a list of available serial ports, run the following command:

python3 -m serial.tools.list_ports

One of them should be the device we want to communicate with. You can specify the device port in the following command in order to initiate the connection.

python3 -m serial.tools.miniterm <device_port> 115200

Here are a few potential examples:

# Windows
python3 -m serial.tools.miniterm COM3 115200
# macOS
python3 -m serial.tools.miniterm /dev/TODO_what_goes_here 115200
# Linux
python3 -m serial.tools.miniterm /dev/ttyUSB0 115200