Using I2C Addresses As Chip Selects

March 27, 2015 by Elliot Williams 42 Comments

I2C has a seven-bit address space, and you’re thinking “when do I ever need more than 127 devices on a pair of wires?” So you order up some parts only to find that they have one, two, or three user-configurable address pins for any given device type. And you need a bunch more than four or eight capacitive sensor buttons on your project. What do you do?

If you’re reader [Marv G], you think outside the box and realize that you can change the addresses on the fly by toggling address pins high and low with your microcontroller. That is, you can use a single I2C address pin for each device as a chip select signal just like you would have with SPI.

That’s it, really. [Marv G] goes through all of the other possible options in his writeup, and they’re all unsavory: multiple I2C busses, a multiplexer, buying different sensors, or changing micros. None of these are as straightforward as just running some more wires and toggling these with your micro.

We’d even go so far as to suggest that you could fan these chip select lines out with a shift register or one of those 1-of-N decoder chips, depending on how many I2C devices you need to chip-selectify. (We’re thinking 74HC595 or 74HC154.)

Along the way, we found this nice list of the number of address pins for a bunch of common peripherals provided by [LadyAda], in case you don’t believe us about how ubiquitous this problem is. How many devices on that list have one (1!!) address pin?

At the end of his post, [Marv G] asks if anyone else has thought of this chip select trick before. We hadn’t. Here’s your chance to play the smart-ass in the comments.

Re-purposing Old Electronics To Inspire New Designs

March 27, 2015 by James Hobson 15 Comments

We love seeing how things work. Exploded views are like mechanical eye-candy to most engineers, so when [Chris’] Kindle Touch died, he decided to give it new life… on his wall.

Inspired by others, he decided to mount all the components of his Kindle onto a piece of plastic that he could hang up on his wall. As an electronics design engineer, he’s always looking for new ideas and ways to design and build circuits — what better way to inspire creativity than to see a real product blown apart? Does anyone remember reading [Stephen Biesty’s] Incredible Cross Sections or Incredible Explosions as a child?

The construction is quite simple, relying on mounting holes where possible to screw parts directly to the board, or by using heavy duty double-sided tape. After finishing the Kindle, [Chris] found an old iPod of his and decided to give it the same ritual.

For some more in-depth exploded physical models, take a look Bolt.io’s office art we covered last year!

Training Fish To Feed Themselves

March 26, 2015 by Anool Mahidharia 41 Comments

We’ve featured quite a few aquarium and fish feeder hacks on our blog. [RoboPandaPDX] thought of taking it up a notch and make an interactive fish feeder. He built a Fish feeder that train’s them to feed themselves.

A copper bar hangs from the middle of a metal cylinder – much like a bell. The end of the bar has a fish lure. When a fish pushes the lure, the copper bar touches the metal cylinder and closes the circuit. This signal goes to an Arduino. To catch the attention of the fishes and to “teach” them, an RGB LED is used. The fish need to figure out that the feeder will dispense food only when the LED is ON and the Lure is pushed. If the fish figure that out, and push the lure when the LED is on, a servo is activated which pushes the feeder to deliver 1 unit of fish food. While at it, he added a couple of bells and whistles. A buzzer to indicate when the Lure switch is closed and a 2 line LCD shows how many times the switch has been activated and how long the program has been running.

A Sparkfun open logger stores the hit count and the minutes and seconds of the hit for data analysis later on. The good news is that it seems to be working. The current code activates the feeder for 30 to 60 minutes every day, which is indicated by the LED. At the end of 9 days, [RoboPandaPDX] found that the goldfish would hit the Lure when the LED turned on, and then turn around to face where the feeder would dispense food in to the tank. His next plan is to put up some obstacles along the path to see if the fish learn some new tricks. His schematic looks a little iffy (the Lure switch is connected to the RST pin of the Arduino), and it seems he cannot remember why he ever did that. He’s happy that it works though, but we’re sure that’s not the right way to wire it up.

[RoboPandaPDX] is looking for suggestions on improving his interactive feeder, so if you have any, do add them in the comments below.

If you need some more fish feeder ideas, check out this and this that we blogged about earlier.

A Laptop With An External Graphics Card?

March 26, 2015 by James Hobson 80 Comments

It used to be that desktop computers reigned king in the world of powerful computing, and to some extent, they still do. But laptops are pretty powerful these days, and in our experience, a lot of engineering companies have actually swapped over to them for resource hungry 3D CAD applications — But what if you still need a bit more power?

Well, [Kamueone] wasn’t satisfied with the performance of his Razer Blade GTX870m laptop, so he decided to hack it and give it its own external graphics card.

Now unfortunately this really isn’t quite a simple as running some PCIE extender cables — nope. You’ll have to modify the BIOS first, which according to [Kamueone], isn’t that bad. But after that’s done you’ll also need a way to mount your graphics card outside of the laptop. He’s using an EXP GDC Beast V6 which uses a mini PCIE cable that can be connected directly to the laptop motherboard. You’re also going to need an external power supply.

[Kamueone] ran some benchmarks and upgrading from the stock onboard GTX870m to an external GTX 780ti resulted in over three times the frame rate capability — 40fps stock, 130fps upgraded!

SparkFun Stair Climbing Robot Challenge

March 26, 2015 by James Hobson 5 Comments

In case you missed it, SparkFun recently held the Actobotics Stair Climber Challenge competition, where you could build a robot capable of ascending stairs and win some sweet SparkFun cash!

The contest is over now and the winners have just been announced — and some of the bots the contestants came up with are just plain awesome!

First prize went to the [Jaeger Family] who built a wheeled robot that can roll right up stairs without even batting an eyelash — it’s pretty cool to see. Check that out and more below.

Continue reading “SparkFun Stair Climbing Robot Challenge” →

Caption CERN Contest Enters Week 8

March 26, 2015 by Adam Fabio 25 Comments

The Caption CERN Contest has been going great guns thanks to the community of users over on Hackaday.io. The contest just finished up its seventh week of finding funny captions for images which CERN has in their archives. CERN has decades of great photo documentation of their projects. Unfortunately they don’t know which project each image goes with, or who exactly is in the image. We’re helping them out where we can, by letting CERN know any information we can find on their photos. We’re also having some fun along the way, by giving out a T-Shirt for the best caption each week.

Here are some of the best quotes from week 7

The Funnies:

“Are Socks and Sandals acceptable safety equipment for the Demolition Pit? Yes, because these are Kelvar socks and Zylon sandals being testing. Quite uncomfortable, but these feet will survive a close proximity blast.” – [controlmypad]

“Check it out! One tube for each Ninja Turtle” – [OzQube]

“Before the LHC, hunting for the Higgs was much less glamorous.” – [Tachyon]

The winner of course is [Tim] with the featured image at the top of this article.

If [Tachyon] sounds familiar, that’s because he came up with the best caption back in week 6. Runners up for week 6 were:

“Damn Mario Brothers ….. ‘gotta save the princess’ How about watching where you’re going for once. – [Scott Galvin]

“Here at CERN, you don’t get shafted. You get tubed.” – [Rollyn01]

“Thank god the separator caught him. Another 50 meters, and he’d be nothing but quarks.” – [Curtis Carlsen]

Click past the break to check out this week’s image!

Continue reading “Caption CERN Contest Enters Week 8” →

Generating The Mandelbrot Set With IBM Mainframes

March 26, 2015 by Brian Benchoff 34 Comments

[Ken Shirriff] is apparently very cool, and when he found out the Computer History Museum had a working IBM 1401 mainframe, he decided to write a program. Not just any program, mind you; one that would generate a Mandelbrot fractal on a line printer.

The IBM 1401 is an odd beast. Even though it’s a fully transistorized computer, these transistors are germanium. These transistors are stuffed onto tiny cards with resistors, caps, and diodes, than then stuck in a pull-out card cage that, in IBM parlance, is called a ‘gate’. The computer used decimal arithmetic, and things like ‘bytes’ wouldn’t be standard for 20 years after this computer was designed – 4,000 characters of memory are stored in a 6-bit binary coded decimal format.

To the modern eye, the 1401 appears to be a very odd machine, but thanks to the ROPE compiler, [Ken] was able to develop his code and run it before committing it to punched cards. An IBM 029 keypunch was used to send the code from a PC to cards with the help of some USB-controlled relays.

With the deck of cards properly sorted, the 1401 was powered up, the cards loaded, and the impressive ‘Load’ button pressed. After 12 minutes of a line printer hammering out characters one at a time, a Mandelbrot fractal appears from a line printer. Interestingly, the first image of the Mandelbrot set was printed off a line printer in 1978. The IBM 1401 was introduced nearly 20 years before that.