Oct 19

Updates in the world of Open Source Laser Tag

To quote GLaDOS, "It's been a long time."

While I've been away, there have been plenty of things going on in the world of open source, laser tag, etc. A quick google search showed me some recent developments that look exciting.

Skirmos is an open source laser tag game made by college students. It is based on the arduino, uses IR LED's to send tags (with a range of 500 feet according to their kickstarter page), X-bee radios to sync data, tricolor LED's for coloring the tag unit, has a screen (which seems to be their differentiator), and has a cool shell. Since it uses an arduino, it is hack-tastic for other arduino enthusiasts. I missed the initial kickstater, and will have to follow up with this in the future. Based on their website and kickstarter goals, the final product may not have all of the functionality that they state in their kickstarter video. But hey, they are building something cool, and I am supportive of building cool things.

The guys at Skirmos mention that they are working with Kevin Darrah. He's another person who has a tutorial for using those silly NRF24L01+ radios (and I say that they are silly because, while I have read their data sheet and understand how one could control them, I haven't spent the time to write a library for controlling them and don't want to. I want a free one that I can use for whatever I want. Including teaching children how to build laser tag). Kevin has a website here with some cool projects relating to LED cubes (shift registers, multiplexing, etc.) and some home automation stuff with the aforementioned radios (which turns out are really cheap on ebay). He also made a breakout board for those things. Because who wants to solder 8 pins every time they use one?

IBM developerWorks has a three part tutorial on building laser tag. Who knew? I had some trouble navigating from part 1 to part 2 (there wasn't a link from part 1 to part 2 that I found faster than googling for part 2, so I'm posting the links to all 3 parts). I may have to look at developerWorks from IBM for more cool projects.
Part 1
Part 2
Part 3

May 02

Quadcopters, mini and otherwise

I saw an article about a mini quadcopter that uses an ATMega128RFA1 (8 bit processor with built in 2.4 GHz transceiver). It's pretty cool, though the website didn't have a lot of build information in the post (there's some more stuff in his earlier posts, but it's not a clear cut thing to look at and know how to build your own without previous knowledge. Maybe I didn't look long enough.) Good instructions or not, it's a sweet project.

Speaking of Quadrotor helicopters, there's a nice youtube series done by The Crash Cast about building a tricopter (three rotor helicopter). If I ever have time to build one, after all of my other projects, then this is where I'd start. Maybe after I'm done teaching about registers and bits I can start teaching about PID controllers with this. How cool would of an advanced project would a quadcopter helicopter be (or tricopter. I don't judge)?

Apr 18

Board to use for permanent Laser Tag modules

I would like to have a stand-alone board to put in the laser tag modules instead of an arduino. This would allow students to use the arduino that they use in class for other projects while keeping the laser tag module intact. Right now I have two alternatives:

Moteino: Cost: $18.95. Uses surface mount components for a really small footprint (1.3x0.9 inches), ATMega328P processor, RFM12B tranceiver. This is the lowest cost module that I could find (as opposed to the JeeNode, which is 18 euros, and has a much larger footprint). I would need an FTDI adapter (or just use the one in the arduino to program it) to program the module, but that's fine. The Moteino also has a version without the RFM12B, which is $12.95.
Update: Low Power Lab is working on an ATMega32u4 based Moteino called the Moteeino Leo, which will probably be less expensive (since it's USB native). Keep an eye out for this.

Freakduino: Cost: $33. Freakduino is an open source arduino clone with an on board 2.4GHz radio (the Atmel AT86RF230). It has a great datasheet, and is a bit bigger than a standard arduino. It's a little pricier, but I like that it can have a longer range by adding an antenna.

miniSWARM: Cost: $25. miniSWARM is an open source arduino compatible with a 2.4GHz radio built into the chip. As of this posting, it is on Indiegogo for crowd funding. It can be used to build a mesh network and is based on the ATmega128RFA1. They are also giving away some miniSWARMs away on their website. This module has much more capability than I need for my application, but it may be useful if I want a mesh network and a much more complicated game.

Note: Both of these alternatives have built in radios for communicating with a central hub, which would keep track of tags. I could not have a wireless module and have all the communication between the central hub, bases, etc be done through IR. It'd be more protocol to write, but I can do it. Just not sure if I want the added flexibility of getting data from players as they play the game.

Later Note: The Waspmote is a commercial wireless sensor node based of the ATMega1281, which is arduino compatible. ATMega processors can be used for real, commercial applications. Fun fact to know.

Processor Note: So, I'm using an ATMega328p when I don't need that much functionality. I mean, I need 1 hardware timer, at least 10 I/O pins (if I put a 7-seg LED on it, or other peripherals), and some program space. But switching to an ATTiny could prove prohibitively complicated in the context of an introductory course. I don't want to have people programming an AVR with an arduino just to get a smaller microprocessor. It's a nice thought to use something with less capability because I don't need the capability, but if I end up expanding this project, it'll be nice to have excess program space and I/O pins to play around with. And who knows, maybe I'll need another hardware timer.

Apr 01

RFduino, single chip arduino and Bluetooth

The RFduino is an arduino compatible made using the Nordic 32-bit ARM Cortex-M0 processor. The cool thing about this is that it can run arduino code and has bluetooth built in. If I can find something like this that can do RF mesh networking (or maybe bluetooth can be used, though it's usually for short range applications) so I can make wireless sensor nodes/laser tag modules that can communicate to a central hub. Just an idea.

Mar 26

ATmega32U4 vs ATmega328P

I am thinking about using an ATmega32U4 instead of the ATmega328P for my laser tag project. The main advantage of the 32U would be built in USB (at the cost of built in serial hardware. Oh darn, I can use software serial. Not a big deal). The 32U is also twice as expensive. The table below summarizes the differences that matter for the laser tag project (there are many differences. I only care about the ones that my project needs. Mainly, programmability and cost; both chips have the functionality that I need).

Microprocessor ATmega32U4 ATmega328P
USB Yes No
Serial (hardware) No Yes
Price (Quantity = 1) $6.04 $3.05
Price (Quantity = 100) $3.42 $1.73
Barebones Arduino $22.95 (adafruit) $29.95 (adafruit)

But, of course, there are similarities. Both chips have 32 kB of flash memory for storing programs, and both have hardware timers, PWM and enough output for the basic laser tag game that I want to implement. Therefore, since both of these chips have these properties, this information has no effect on my decision because it does not help me distinguish which alternative is better.

Both processors are supported (can be programmed with) the arduino IDE, which makes my life a lot easier. Since the 32U doesn't need an FTDI chip for USB to serial conversion, it saves about $15 for the cost of the board. As of now, I should use the 32U instead of the 328P, since it will make the device cheaper by implementing USB communication on chip.

Dangerous Prototypes posted an article about Paperduino, an arduino Leonardo (Leonardo uses the 32U) clone. It has a cool tutorial on putting a paper label onto the board as well, which is a nice touch. For more information on the 32U4 and the Leonardo, the guys at arduino posted a great article.

Mar 21

The terror of the Snooze Button

Lifehacker posted a video today by ASAP Science (they have a Youtube channel) about how the snooze button doesn't help you get any more sleep and can actually make you more tired. This adds to my convictions that the alarm clock that I make will not have a snooze button. It will wake me up, whether I want it to or not. And as the saying goes, "The me in the morning will have no respect for the me that set the alarm."

Mar 15

RFM12B Wireless Modules

Over the months, I've ran across a number of wireless modules, each telling me different things about their capabilities. There's the XBee, a great module that has books written to teach people how to use it. They come in many flavors and have a lot of breakout boards. They are also $17 for the low power version or $28 for the Xbee Pro, according to digi.com. Then there's the Nordic nRF24L01, which is a low cost module with an arduino library. They cost $4.75 (on sale now at yourduino.com for $2.75. Nice) Lower cost, but more difficult to set up for the beginner (there are code samples, people have used these before).

I recently came across the RFM12B. It's $6.95 at Sparkfun, but I doubt that's as cheap as one can find them, since Sparkfun usually is a bit more expensive than other suppliers (I have nothing against them. They were one of the first suppliers to carry arduinos, and I appreciate that. I also look for bargains). It also has a library (created by Low Power Lab based on the JeeLabs RFM12B library), which is completely open source (MIT license, so the code that uses it must also be open source, but since my project is open source too, that doesn't matter). Not sure whether or not it will be easier to use than the nRF24L01, but it's worth looking into if I make all the laser tag modules use RF to communicate hits to a central hub. That'll happen later in the process, after the core functionality is ironed out. Potentially, IR communication could be all I use for my open source laser tag project (note, OpenTag is a  DASH7 protocol stack, which is an open source wireless network standard. Damn. Can't use that name), so I won't need to have a wireless module on the units.

Note: the guy over at Low Power Lab is manufacturing an arduino clone with a RFM12B wireless module called the Moteino. He has some videos about soldering the Moteinos  (along with the stencil he uses to apply the solder paste) along with the iTeadStudio PCB's that he's using. Check out his blog at lowpowerlab.com.

You can also build a DIY laser cutter that can cut stencils. The tutorial is here.