Traceroute scraper in Processing

There are many web-based interfaces to traceroute available, including a nice list at  Here’s a Processing sketch that retrieves the raw HTML from one of them and separates the traceroute lines into time taken, hop IP, and hop name.

This sketch can be modified to scrape other web-based traceroute apps, but you’d need to change the last two methods, parseHop() and printHopList(), depending on how your particular app formats the results. You’d also need to change the global variables at the top that pertain to the site being used.

One caveat: the traceroute takes some time.

To see the full output of the HTML call, change debug to true.

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Chat Server in Processing

Here’s a basic chat server written in Processing.  It’s a bit more complex than the basic test server.  This server keeps track of all the clients who log into it in an ArrayList.  Using an ArrayList is useful when you need to do more complex things with the clients, as in my pong server from Making Things Talk. This is the most minimal server I could come up with that keeps a list of its clients.

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CNMAT resources archive

Berkeley’s CNMAT (center for new music and audio technologies) has a nice resource archive, with pictures.  Useful if you’re looking for electronic parts, microphones, and other things audio-related.  Similar to RISDpedia and ITPedia, among others, very useful.  Thanks to Tom Gerhardt and Adrian Freed for the link.

A Few Good Reasons Why Peter Knight Rocks

Peter Knight works with Massimo and Alex and co. at He’s written some great AVR code, which is useful in Arduino.  For example:

Secret Thermometer takes advantage of the ATMega’s internal thermometer. Turns your ‘328-based Arduino into a thermometer with no extra parts.

Secret Voltmeter same idea, but this reads the internal analog-to-digital converter to tell you the Arduino’s supply voltage. Also works on the ATMega168.

He’s also done Cantarino, a speech synthesis engine; Auduino, a granular sound synthesis engine; a DMX library; and more.  Check them all out at the code repository.

Controlling Lots of Outputs from a Microcontroller

Making LED displays is fun. There are a a few tools that get used all the time, from row-column scanning to LED driver chips to multplexers and shift registers. This tutorial discusses some of the more popular methods for controlling large amounts of LEDs from a microcontroller, including their various strengths and weaknesses, and how they work. For more on this subject see chapter 14 of “Physical Computing“, where Dan O’Sullivan and I discussed it in more depth.  I’ll also include some notes on how to apply these ideas to controlling multiple motors or other high-current loads.

Most microcontroller modules have a limited number of outputs. Even if you use the analog inputs as digital I/O, there are only 19 pins on an Arduino, for example. That’s a fairly typical number for an 8-bit controller, and it seems not nearly enough if you want to control, say, 100 LEDs or more.  There are a couple ways around this problem.  Without adding any additional hardware, you can make a matrix of your LEDs and control them using row-column scanning.  If you want discrete analog control over one output at a time, you can use a multiplexer. For digital control over multiple pins, you could use an addressable latch or a shift register. If you need pseudo-analog control over multiple pins, you could use a PWM driver.  There are also several LED driver chips that are designed specifically to control groups of LEDS.

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