Arnaud Durand DurandA

Calling `alert` from WebAssembly (WASM)

This very simple and minimal tutorial documents in a few easy steps how to play with WebAssembly (WASM) and get first results within minutes.

While the code below is mostly useless, it will show, how to call the alert function from within a WASM file and thus demonstrate how to import and export DOM objects.

Of course, this exercise has no real use. It is just meant to show, that getting started with WASM isn't hard. And there is no need for a complex build-chain, tons of tools or a dedicated VMs. Just use a browser, one online tool and that's it.

And Now?

Certificate CA Validation

The easy way

To validate a certificate agains a certificate authority you just have to run

openssl verify -trusted ca_root.pem -untrusted intermediate_ca.pem certificate.pem

You'll see a 'OK' message at the end of the output

Setup Wireless LAN for Raspberry Pi

The following guide describes how to setup Raspberry Pi to connect to Wifi. It was tested on the following environment:

Raspberry Pi Model B
Edimax EW-7811Un USB Wifi dongle
OS: Raspbian Jessie

Here are the overview of the steps:

	# Download and install BlueZ 5.43 and libreadline7 packages

	wget http://mirrors.kernel.org/ubuntu/pool/main/r/readline/libreadline7_7.0-0ubuntu2_amd64.deb
	wget http://ftp.debian.org/debian/pool/main/b/bluez/bluez_5.43-1_amd64.deb
	sudo dpkg -i libreadline7_7.0-0ubuntu2_amd64.deb
	sudo dpkg -i bluez_5.43-1_amd64.deb

	# Restart system or BlueZ service

	# Enable chrome://flags/#enable-experimental-web-platform-features and restart Chrome

	APP = hello
	APP_MODULES = src
	APP_FS_PATH = $(CURDIR)/fs
	APP_CONF_SCHEMA = $(CURDIR)/src/conf_schema.yaml
	MG_ENABLE_JS = 0
	MG_ENABLE_CLUBBY = 0

	MG_FEATURES = -DMG_ENABLE_HTTP_STREAMING_MULTIPART \
	-DMG_NO_BSD_SOCKETS \
	-DMG_LOCALS \

	import asyncio
	from aiohttp import web
	import subprocess


	async def uptime_handler(request):
	# http://HOST:PORT/?interval=90
	interval = int(request.GET.get('interval', 1))

	# Without the Content-Type, most (all?) browsers will not render

	/*
	servo controller
	Based on code from Mojo tutorial
	https://embeddedmicro.com/tutorials/mojo/servos

	Takes an 8-bit position as an input
	Output a single pwm signal with period of ~20ms
	Pulse width = 1ms -> 2ms full scale. 1.5ms is center position
	*/
	module servo_controller (

	#!/usr/bin/python3
	import quick2wire.i2c as i2c
	import time
	import RPi.GPIO as GPIO
	import alsaaudio
	import threading
	import logging
	import sys

	#Work in progress library for Si473x for Raspberry Pi by Jonathan Thorpe <[email protected]>

	#!/usr/bin/env python

	"""Simple HTTP Server With Upload.

	This module builds on BaseHTTPServer by implementing the standard GET
	and HEAD requests in a fairly straightforward manner.

	"""