savetheclocktower

Using a rotary encoder as a volume control

On my RetroPie machine I wanted a hardware volume knob — the games I play use a handful of emulators, and there's no unified software interface for controlling the volume. The speakers I got for my cabinet are great, but don't have their own hardware volume knob. So with a bunch of googling and trial and error, I figured out what I need to pull this off: a rotary encoder and a daemon that listens for the signals it sends.

Rotary encoder

A rotary encoder is like the standard potentiometer (i.e., analog volume knob) we all know, except (a) you can keep turning it in either direction for as long as you want, and thus (b) it talks to the RPi differently than a potentiometer would.

I picked up this one from Adafruit, but there are plenty others available. This rotary encoder also lets you push the knob in and treats that like a button press, so I figured that would be useful for toggling mute on and off.

warpling

//
//  CircularTextView.h
//  Wormhole
//
//  Created by Ryan McLeod on 5/5/15.
//  Copyright (c) 2015 Ryan McLeod. All rights reserved.
//

#import <UIKit/UIKit.h>

samsonjs

// Taken from the commercial iOS PDF framework http://pspdfkit.com.
// Copyright (c) 2014 Peter Steinberger, PSPDFKit GmbH. All rights reserved.
// Licensed under MIT (http://opensource.org/licenses/MIT)
//
// You should only use this in debug builds. It doesn't use private API, but I wouldn't ship it.

#import <UIKit/UIKit.h>
#import <objc/runtime.h>
#import <objc/message.h>

FredrikSjoberg

// https://www.cs.rit.edu/~ncs/color/t_convert.html
struct RGB {
    // Percent
    let r: Float // [0,1]
    let g: Float // [0,1]
    let b: Float // [0,1]
    
    static func hsv(r: Float, g: Float, b: Float) -> HSV {
        let min = r < g ? (r < b ? r : b) : (g < b ? g : b)
        let max = r > g ? (r > b ? r : b) : (g > b ? g : b)

jasonpincin

Anivia

Anivia is Walmart's mobile analytics platform. It collects user-interaction metrics from mobile devices -- iPhone, iPad, Android, and mWeb. It also processes logging and other metrics from a bunch of mobile services. Anivia allows the business to have real-time insight and reporting into what is going on in the mobile business and provides vital capabilities for developers and ops folks to monitor the health of their services.

Anivia is built on Node.js, Hapi, RabbitMQ, and a multitude of downstream systems including Splunk and Omniture. Anivia is taking in 7,000 events per second on average (as of this writing), which after some fan-out and demuxing comes out to around 20,000 messages per second in flight. These rates are expected to soar leading up to and including Black Friday. The platform has grown in recent months to over 1,000 node processes spanning multiple data centers, gaining features such as link resiliency in the process.

A few of Anivia's functionalities

• __Timestamp Correc

milend

// https://en.wikipedia.org/wiki/Damping
double HTSpringOverdamped(double time, double damping, double freq, double offset, double velocity) {
	NSCParameterAssert(0.0 <= damping);
	NSCParameterAssert(damping < 1.0);
	
	if(time <= 0.0)
		return offset;
	
	const double wd = freq * (2.0 * M_PI);
	const double w0 = wd / sqrt(1.0 - damping * damping);

davist11

56k: "https://123.campfirenow.com/images/56k.gif"
bell: ":bell:"
bezos: ":laughing::thought_balloon:"
bueller: "anyone?"
butts: ":open_hands: :smoking:"
clowntown: "https://123.campfirenow.com/images/clowntown.gif"
cottoneyejoe: ":notes::hear_no_evil::notes:"
crickets: "hears crickets chirping"
dadgummit: "dad gummit!! :fishing_pole_and_fish:"
dangerzone: "https://123.campfirenow.com/images/dangerzone.png"