Building A PDA From Scratch

Extremely powerful ARM microcontrollers have been around for ages now, but only recently have they been available for just a few dollars with a good enough toolchain for some serious development work. [Jose] wanted to develop something awesome with an ARM chip he had lying around, so he built a PDA (Spanish, translation) that can be used as a game console, an oscilloscope, a clock, or a wristwatch. Basically, it’s a portable homebrew computer that can do just about anything.

The hardware is built around an ARM Cortex M4 chip clocked at 170MHz. Included on the PCB is an SD card slot, a JTAG interface, a USB port (only used for charging the battery at this point), and a touch screen LCD controller.

After designing the PCB and enclosure, [Jose] looked around the Internet for a decent GUI library without much success. He eventually found Gwen, a lightweight library for programming GUIs that is easily ported to [Jose]’s hardware.

So far, [Jose] has a few GUI demos up and running on his homebrew PDA, but nothing very useful yet. Still, the fact that [Jose] can get a full-featured ARM tablet-like piece of hardware off the ground without a team of developers brings a smile to our face. We can’t wait to see the state of homebrew ARM devices in a few years when everyone has the requisite hardware and software knowledge.

Labor Day Weekend Water Gun Spectacular

In the US, summer is marked by two holidays. In late May, Memorial day traditionally marks the the beginning of summer, the opening of public pools, and the day shopping malls are invaded by scores of petulant teenagers. In early September, Labor day marks the traditional end of summer, a great weekend to fire up the grill, and finally – finally – an end to the neighborhood kids screaming their heads off outside. Being Labor day weekend, we were very happy to see two builds show up in the tip jar concerning the one object that defines summer: water guns.

Homemade Super Soaker

[Michael] had the genius idea of building a water gun out of a diaphragm expansion tank (German, here’s the terrible translation). These tanks – usually connected to a house’s hot water line near the hot water heater – allow for the expansion of hot water and protects pipes from excessive pressure. It does this with a rubber membrane separating the inside the tank into two halves. Half the tank is filled with water while the other half is filled with compressed air from a bicycle pump.

[Michael] connected a hose and made a nice gun out of aluminum pipe to build the ‘gun’ part of his build. With 9 bar of pressure in the expansion tank, [Michael] can shoot a stream of water 20 meters.

Water gun turret with a laser sight

This build comes from [Valentin]. He picked up a automobile water pump for just a few Euros, and attached it to a 1 liter bottle filled with water. A pan/tilt turret was constructed out of CNC milled aluminum and a pair of servos.

After [Valentin] got the water-shooting turret part of the build out of the way, he installed a 2.4 GHz wireless camera on the pan/tilt mount and taped a receiver to the back of his remote control.

The addition of a small LCD screen displaying the turret’s point of view makes for a very cool build, perfect for pestering those annoying neighborhood kids.

Video of [Valentin]’s build after the break.

Continue reading “Labor Day Weekend Water Gun Spectacular”

Lazy Labor Day Educational Time. Watch Cornell’s Microcontroller Courses.


C’mon, you know you’re not really going to do much today. You might as well spend that time learning some skills instead of watching funny cats. The Cornell ECE lectures on microcontrollers (ECE 4760 and ECE5760), taught by [Bruce Land], are available online for free.

Not only do you get to enjoy these two courses, but there are videos available showing off several different categories of student projects as well.

Continue reading “Lazy Labor Day Educational Time. Watch Cornell’s Microcontroller Courses.”

Raspberry Pi - rpi

Operating Systems Development With The Raspberry Pi

Even though the Raspberry Pi has, from the very beginning, been touted as an educational computer, we’ve seen neither hide nor hare of coursework, lesson plans, or even computer sciencey tutorials using the Raspi. We’re guessing academia works at a much slower pace than the average hardware hacker, but [Alex Chadwick] at Cambridge University has managed to put together an online tutorial on developing an operating system from scratch for the Raspi.

The goal of this tutorial is to throw a budding Raspi tinkerer into the strange and confusing world of registers, hexadecimal, and ARMv6 assembly. After going through the necessary toolchain, [Alex]’s tutorials cover blinking the ‘OK’ LED on the Raspberry Pi using only assembly.

The OS development guide goes on from there to include drawing graphics on the screen and even accepting input from a USB keyboard.

It’s important to point out what [Alex]’s tutorial isn’t; even though this series of tutorials goes through manipulating the bare metal of the Raspberry Pi, don’t expect to be porting UNIX to the Raspi after going through these guides. That being said, after completing these tutorials, you’ll be in a fabulous position for building your own homebrew OS on the Raspberry Pi.