12 March 2022

Detecting Badger2040 boards and automating uploads

I recently bought a bunch of Pimoroni Badger2040 boards, and they are a lot of fun.

The Badger is basically a small microcontroller (the Raspberry Pico) with an eInk display, in the size of a typical office badge. It has a few buttons you can interact with, when powered, but because of eInk it doesn't actually need to be powered all the time - you can just set it to the desired screen, turn off the battery, and the screen will stay as it was more or less forever.

The fun bit is that it can run MicroPython, so programming it is a breeze. You don't have to deal with all the scary vagaries of C/C++; just write your Python scripts, save them to the board, and run them. Sweet!

There is already a fairly comprehensive tutorial on how to get started with Badger2040, but (like most Pico-related documentation out there) it assumes you're happy to use Thonny, an editor focused on the micropython ecosystem, in order to move files to the board. With all due respect, Thonny is a very limited editor, and it gets recommended only because it's the most intuitive when it comes to managing files on the Pico. I'm much happier when I live in my beloved PyCharm, but its MicroPython plugin is somewhat limited and requires manual interaction, so I investigated a strategy to automate the basic stuff directly from Python on my laptop.

The first step is detecting the board. It appears to the operating system as a serial port, so we have to list the available ports and find the one that looks like our guy.

 # badgerutils.py
import serial.tools.list_ports as list_ports
from serial.tools.list_ports_common import ListPortInfo
def is_badger(port: ListPortInfo):
    """ decide if the port looks like a Badger2040 """
    # mac, but other systems will probably be similar,
    # just add other "if" blocks for windows etc
    if sys.platform.startswith('darwin'):
    	# you should be more thorough, 
        # might want to check VID etc, but this will do for dev
        if port.manufacturer and \
            return True
    return False
def get_badger():
    """ loop through all the ports and find our board """
    ports = list(list_ports.comports())
    for p in ports:
        if is_badger(p):
            return p

The next step is where things get a bit hairy. Interacting over the serial port is not everyone's idea of fun, so we better stand on the shoulder of geeky giants if possible. We could dig through Thonny's code, but it's long and complicated and meant to support a lot of scenarios we don't really care about. Instead, we can reuse a little utility called ampy, which is slightly old but fairly robust and (more importantly) self-contained and easy to understand.

Ampy includes a couple of modules to interact with a micropython board. You can have a look at the functions found in its cli module to figure how to wrap them, but here's a simple approach to start pushing files to the board - some of the code is lifted almost entirely from ampy.cli, but it's MIT-licensed, so you can do that (just mention the original copyright notice somewhere, if you publish it!).

# BadgerManager.py
from serial.tools.list_ports_common import ListPortInfo
from ampy.files import Files, DirectoryExistsError
from ampy.pyboard import Pyboard
class MyBadger(Pyboard):

    def __init__(self, port: ListPortInfo):
        super(MyBadger, self).__init__(port.device)
        self.files = Files(self)

    def upload(self, file_path: Path, dest_path: Path):
        """ upload file or directory to board """
        if file_path.is_dir():
            # Directory copy, create the directory and walk all children 
            # to copy over the files. 
            for parent, child_dirs, child_files in os.walk(file_path):
                # Create board filesystem absolute path to parent directory.
                remote_parent = posixpath.normpath(
                    posixpath.join(dest_path, os.path.relpath(parent, file_path))
                    # Create remote parent directory.
                except DirectoryExistsError:
                    # Ignore errors for directories that already exist.
                # Loop through all the files and put them on the board too.
                for filename in child_files:
                    with open(os.path.join(parent, filename), "rb") as infile:
                        remote_filename = posixpath.join(remote_parent,
                        self.files.put(remote_filename, infile.read())
            # File copy
            # check if in subfolder
            if len(dest_path.parents) > 1:
                # subfolder was specified
                # each parent has to be created individually,
                # because of ampy limitations
                for d in sorted(dest_path.parents)[1:]:  # first is /, discard

            # Put the file on the board.
            with open(file_path, "rb") as infile:
                self.files.put(dest_path.absolute(), infile.read())

    def ls(self, dirname='/', recurse=True):
        """ List files on board """
        dirpath = dirname if type(dirname) == Path else Path(dirname)
        return self.files.ls(dirpath.absolute(),
                             long_format=False, recursive=recurse)

Putting both things together we can interact very easily with the board like this:

from badgerutils import get_badger
from BadgerManager import MyBadger

# Note: in real life, remember to manage error conditions ! 
port = get_badger()
board = MyBadger(port)
board.upload("./something.txt", "/something.txt")
assert('/something.txt' in board.ls())

Happy hacking!

1 comment:

Tonygo2 said...

Very interesting and useful, Thanks. Tonygo2