Posts

Raspberry Pi Zero boot speed

I enjoy working on embedded systems, but there’s a significant amount of work you have to do in getting the platform ready before getting to the more interesting business logic. The Raspberry Pi Zero W solves most of these problems: it’s small, has decent I/O, a decent price ($10 + $6 for storage + $4 for shipping) and runs full Linux so I can use my current language of choice.

cxx17: working through Cracking the Coding Interview

I’m working my way through Cracking the Coding Interview as a way of learning the new features and tool ecosystem of C++17. Q1.9 reminded me of those games where you need to make a shape by drawing straight lines through dots.

go packages on your own domain

go get has a nice feature where it will fetch the package URL and, based on a meta tag, redirect to the actual location. Here’s the nginx config I use to redirect go get juju.

DFRobot FIT0441 pinout

I ordered two FIT0441 brushless motors for use in v2 of my balancing robot. The DFRobot wiki page on the motor is incorrect so I thought I’d blog about it so someone else can find it 🙂

ESP8266 IO bridge

github.com/eriksl/esp8266-universal-io-bridge looks cool – it exposes the I/O of a ESP8266 wifi module including the GPIO, I2C, PWM, ADC, and UART via a line based telnet interface.

A toy PL/0 compiler

I’ve released a toy compiler for the PL/0 educational language at https://juju.net.nz/src/cgit.cgi/pl0.git/ or https://github.com/nzmichaelh/pl0. I did this as, despite working with compilers for a fair part of my life, I’d never written one from scratch.

Maker Faire Bodensee

We went to Maker Faire Bodensee on the weekend. The kids spent so much time with Paula Pongratz’s Post-apocalyptic jewlery that they missed most of the rest (heh). Other standouts were the breadboard / pus pin based electronic organ from [

Sending music over light

Someone recently mentioned that you can ‘hear’ a TV remote control by hooking a solar panel to a speaker and pointing the remote at it. It was a rainy weekend this weekend, so my son and I gave it a go:

Web connected NeoPixel ring

It’s taken a while (as you can tell from the date on the box), but here’s my web connected NeoPixel ring: https://juju.net.nz/michaelh/blog/wp-content/uploads/2016/02/Vid-20160207-165253-1.m4v Chroma trail: a comet with a trail that cycles through the colours of the rainbow.

Fading text on an OLED screen

Here’s my hack of the moment: text fading in on a OLIMEX 128×64 OLED display. The interesting bit is that this is a TTF font which is rendered by SDL2 into a buffer, dithered into black and white using Floyd-Steinberg error diffusion, and then written out using the Intel IoT upm display driver.