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MicroPython WebAssembly

MicroPython for WebAssembly.

Dependencies

Building webassembly port bears the same requirements as the standard MicroPython ports with the addition of Emscripten (and uglify-js for the minified file).

The output includes micropython.js (a JavaScript wrapper for the MicroPython runtime) and firmware.wasm (actual MicroPython compiled to WASM).

Build instructions

In order to build micropython.js, run:

$ make

To generate the minified file micropython.min.js, run:

$ make min

Running with Node.js

Access the repl with:

$ node build/micropython.js

Stack size may be modified using:

$ node build/micropython.js -X stack=64K

Where stack size may be represented in Bytes, KiB or MiB.

MicroPython scripts may be executed using:

$ node build/micropython.js hello.py

Alternatively micropython.js may by accessed by other javascript programs in node using the require command and the general API outlined below. For example:

var mp_js = require('./build/micropython.js');

mp_js_init(64 * 1024);
mp_js_do_str("print('hello world')\n");

Running with HTML

The prerequisite for browser operation of micropython.js is to listen to the micropython-print event, which is passed data when MicroPython code prints something to stdout. The following code demonstrates basic functionality:

<!doctype html>
<html>
  <head>
    <script src="build/micropython.js"></script>
  </head>
  <body>
    <pre id="micropython-stdout"></pre>
    <script>
      document.addEventListener("micropython-print", function(e) {
        let output = document.getElementById("micropython-stdout");
        output.innerText += new TextDecoder().decode(e.detail);
      }, false);

      var mp_js_startup = Module["onRuntimeInitialized"];
      Module["onRuntimeInitialized"] = async function() {
        mp_js_startup();
        mp_js_init(64 * 1024);
        mp_js_do_str("print('hello world')");
      };
    </script>
  </body>
</html>

MicroPython code execution will suspend the browser so be sure to atomize usage within this environment. Unfortunately interrupts have not been implemented for the browser.

Testing

Run the test suite using:

$ make test

API

The following functions have been exposed to javascript.

mp_js_init(stack_size)

Initialize MicroPython with the given stack size in bytes. This must be called before attempting to interact with MicroPython.

mp_js_do_str(code)

Execute the input code. code must be a string.

mp_js_init_repl()

Initialize MicroPython repl. Must be called before entering characters into the repl.

mp_js_process_char(char)

Input character into MicroPython repl. char must be of type number. This will execute MicroPython code when necessary.

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