I am working on a data logger for the wii nunchuck. I need something to record the accelerometer values that get output from the nunchuck. I had a Microchip 25LC080 eeprom handy and decided to hook it up to my Arduino.

The Arduino site has a great tutorial on working with serial eeproms http://www.arduino.cc/en/Tutorial/SPIEEPROM . I used it to get most of my information. The eeprom I am using is a just little different than the one in the tutorial.

With a little hacking, data can be read from a wii nunchuck directly into an Arduino, using TWI (aka I2C). The nunchuck contains a 3 axis accelerometer, joystick and buttons for only $19.95. The same accelerometer in kit form, cost $34.95 at Sparkfun. Plus the nunchuck is already wired up in a nice clean case! So the wii nunchuck should fit nicely into anyones robotic project.

After some trying, I have been able to use a wiimote for two-way communication for an Arduino. So far I just have a proof of concept. The code is very rough. For the set up and wiring, first look at my earlier entry on using the wiimote for one way communication.

I recently switched from using plain Atmel chips to Arduino. Arduino is a development platform that uses an Atmel Atmege168 chip. It simplifies things a lot.

The Arduino board has a USB port. It has a built in FTDI chip for USB to serial conversions.

This HOWTO shows how to communicate between Perl/Linux and the Arduino. Because of the Arduinos FTDI chip, I can use regular serial communication, I just needed to first set up the USB serial adapter drivers. Most modern linux distro should come with them installed.

The perl script will transmit a number, starting at 0, to the Arduino. The Arduino will then echo that number back to your linux/perl computer.

With a little wiring a Wiimote can be made into a cheap bluetooth transmitter for your microcontroller project. Wiimote peripherals like the nunchuk, communicate with the wiimote over I2C (aka Two Wire Interface, TWI). A number of microcontrollers support TWI, such as the Arduino,the Make Controller and Atmels ATmega series. I am using an arduino with a ATmega168 for this project.

Here is how I controlled a stepper motor with an Atmel attiny2313. I found an old stepper motor in my junk box. I remembered it was a unipolar stepper but that was about it. Google couldn't find the part number, so I had no data sheet.

A unipolar stepper motor has four magnet/coils. Each coil must energize in sequence to spin the motor. The coils are in pairs. Each pair shares a common positive line.

The motor has 6 wires so I had to figure out what each was. The colors where: white, black, blue/red, white/blue, white/black. I pulled out my meter and checked the resistance between each set of wires.

The attiny2313 has a built in UART for serial communication. You need a few outside parts to allow it to communicate with a PC over a serial connection.

I wanted to put my Minipov on something so it would be easy to see the persistence of vision. So I put the minipov board on a piece of flat aluminum and connected it to a 9 volt hobby motor.





Then put a model airplane prop drive adapter on the motor. I drilled a whole in the center of the aluminum and secured it to the motor with the prop drive adapter and just powered it with a 9 volt battery.

I added a hall effect sensor to the minipov so the minipov could sync up with the rotation of the motor. I used ladyadas spokepov code as a reference for how to sync with a hall effect sensor. The hall effect sensor is rated for 3.5 volts, but it will work at 3 volts. My batteries got a little low and the sensor started missing the magnet. It took me a while to figure out that all I needed to do was get a fresh set of batteries (I spent over an hour repositioning the magnet and sensor).

I ordered the Minipov kit from adafruit. POV stands for persistence of vision. Basically flashing seperate images fast enough to make them look like motion.

The kit uses 8 red leds. It is pretty simple to build, it only took about 45 minutes to solder together. It took a little more time than that to install all of the software onto my linux box.

Getting the minipov to display a readable image took some work though. Waving the thing as fast as I could would sort of make a readable image. I slowed the blink rate down some and that helped.

I finally got the hardware watchdog working on my Soekris Net4511. The Soekris box runs my webcam and X10 stuff. I installed Voyage linux on the box. The default sc520_wdt does not work with the watchdog on the Net45* boxes. I found a patch to apply. I didn't write the patch, I found it from a post by Jakub Schmidtke.

Update: It turns out Punky does have this patch in the default build of Voyage linux. I just happened to download a snapshot of voyage that didn't include the patch. Anyway if you want watchdog support on a net4511 give voyage a try. It is a pretty good distro.