Connecting to a Web Serial port under Pyodide

The Pyodide backend exposes the browser’s Web Serial API through the same serialx API you’d use on any other platform. The backend is registered automatically when running under Pyodide, with URIs of the form pyodide://<name>. There is no sync Serial class, the backend is async-only.

Registering a port

Unlike the other platforms, security constraints require user interaction before a reference to a serial port is given to the application. Use navigator.serial.requestPort() in response to a user interaction to get a SerialPort JS object. Once you have a reference to the SerialPort object, register the object with pyodide and attach it to a URI:

const pyodide = await loadPyodide();
const registerJsPort = pyodide.pyimport(
    "serialx.platforms.serial_pyodide"
).register_js_port;

document.getElementById("connect").addEventListener("click", async () => {
    const port = await navigator.serial.requestPort();
    registerJsPort("pyodide://my-device", port);
});

The Python half of your application can now connect to pyodide://my-device using the regular serialx async APIs (see the quickstart):

import serialx

reader, writer = await serialx.open_serial_connection(
    "pyodide://my-device",
    baudrate=115200,
)

writer.write(b"ping")
data = await reader.readexactly(4)