In this guide, we will walk you through the process of setting up an HTTPS web server on the Raspberry Pi Pico W. This will allow you to securely serve web pages from your Raspberry Pi Pico W. We will be using the MicroPython firmware and the popular web framework Flask. This guide assumes that you have some basic knowledge of Python and that you have already set up your Raspberry Pi Pico W with MicroPython.

Installing the Required Libraries

In order to set up an HTTPS web server on your Raspberry Pi Pico W, you will need to install the Flask and cryptography libraries. You can do this by connecting to your Raspberry Pi Pico W using a serial connection and running the following commands:

import upip
upip.install('flask')
upip.install('cryptography')

Creating a Self-Signed SSL Certificate

The next step is to create a self-signed SSL certificate for your web server. This will allow you to use HTTPS to securely serve web pages. To do this, run the following code:

from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives import serialization
from cryptography.hazmat.primitives.asymmetric import rsa
from cryptography.x509.oid import ExtensionOID, NameOID
from cryptography.x509 import (
    CertificateSigningRequest,
    BasicConstraints,
    Name,
    Extension,
    CertificateBuilder,
)

private_key = rsa.generate_private_key(
    public_exponent=65537,
    key_size=2048,
    backend=default_backend()
)

certificate = CertificateBuilder().subject_name(
    Name([
        NameOID.COMMON_NAME,
        b'example.com',
    ])
).issuer_name(
    Name([
        NameOID.COMMON_NAME,
        b'example.com',
    ])
).add_extension(
    Extension(
        ExtensionOID.BASIC_CONSTRAINTS,
        critical=True,
        value=BasicConstraints(ca=False, path_length=None),
    )
).add_extension(
    Extension(
        ExtensionOID.KEY_USAGE,
        critical=True,
        value=certificate.key_usage(
            digital_signature=True,
            content_commitment=True,
            key_encipherment=True,
            data_encipherment=True,
        ),
    )
).add_extension(
    Extension(
        ExtensionOID.SUBJECT_ALTERNATIVE_NAME,
        critical=False,
        value=certificate.subject_alternative_name(b'example.com'),
    )
).sign(private_key, algorithm=certificate.default_signature_algorithm(), backend=default_backend())

certificate_bytes = certificate.public_bytes(serialization.Encoding.PEM)
private_key_bytes = private_key.private_bytes(
    encoding=serialization.Encoding.PEM,
    format=serialization.PrivateFormat.TraditionalOpenSSL,
    encryption_algorithm=serialization.NoEncryption(),
)

with open('cert.pem', 'wb') as f:
    f.write(certificate_bytes)

with open('key.pem', 'wb') as f:
    f.write(private_key_bytes)

This code will create a self-signed SSL certificate for the domain example.com. You will need to replace this with your own domain name. The certificate and private key will be saved to the files cert.pem and key.pem respectively.

Setting Up the Web Server

Now that you have your SSL certificate and private key, you can set up the web server. To do this, run the following code:

from flask import Flask, render_template_string
from flask_sslify import SSLify
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives.asymmetric import rsa
from cryptography.hazmat.primitives import serialization
from cryptography.hazmat.primitives.asymmetric import padding
from cryptography.hazmat.primitives import hmac
from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
from cryptography.hazmat.primitives.hashes import Hash, HMAC, SHA256
from OpenSSL import SSL

app = Flask(__name__)
app.config['SSL_CONTEXT'] = ('cert.pem', 'key.pem')
app.config['DEBUG'] = True
sslify = SSLify(app)

@app.route('/')
def index():
    return render_template_string('
Hello, World!
')

if __name__ == '__main__':
    app.run()

This code creates a new Flask app and sets the SSL context to the certificate and private key that you created earlier. The index() function is the route for the root URL, which will display a simple Hello, World! page.

You can now access your web server using HTTPS by visiting https://example.com in your web browser.

You have now successfully set up an HTTPS web server on your Raspberry Pi Pico W. This guide covered installing the required libraries, creating a self-signed SSL certificate, and setting up the web server. This guide should have provided you with a good understanding of the process and how to set up your own HTTPS web server on the Raspberry Pi Pico W.

References