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Wednesday, October 7, 2015

A close look at pwm input


PWM is used for things like controlling servos, motors and LEDs. Output from a micro-controller is easy, and the hardware usually handles it. Remote control receivers also output it, as they are used to control these things as well. RC transmitters often output the closely related PPM (aka CPPM). It's not unusual to want to read those values with an Arduino microcontroller, but this is not as easy, as common - meaning ATmega328 and similar - hardware doesn't do it directly. So let's look at some options to do that.

Monday, August 10, 2015

Unicode input with X11


Whether you like it or not, Unicode is here. Modern programming languages allow it to be used in variable names and for operator symbols, older ones are adding it as extensions, and inputting it is getting easier all the time.
And frankly, I think most of us would rather read x ≠ 23 instead of x /= 23 or x != 23 or even x =/= 23 . Or how about x ∈ A instead of element(x, A)?
So here's how I set up my X11 keyboard to allow me to input the more popular programming symbols - at least for Haskell - directly from the keyboard, without having to use some editor-specific magic.

Friday, April 17, 2015

Functional Mazes

Long time, no blog!

Wow, it's been a long time since I posted here. Well, I've been involved with rc stuff and 3d printing things.
The latter is what led to this post. I ran into a 3d printed maze that was generated programmatically. The authors comment that trying to do this in OpenSCAD was impossible because it was a functional language.
I had to disagree. First, that OpenSCAD is a functional language. It might have functional inspiration, and the developers try to stay with those principles, but as a functional language, it sucks. So much so that I wrote a Haskell library to generate OpenSCAD from a proper functional language, with static type checking and much better error messages.
Second, I disagree that a maze generator is impossible in a functional language. There was a time in the past - long enough ago that I was working in BASIC, C and PostScript - that I wrote maze generators. So I decided to write one in Haskell. The generator is purely functional, though the State monad is used to hide some of the plumbing.