Wii Nunchuck On An 80s Computer

January 16, 2012 by Brian Benchoff 3 Comments

For a computer that debuted in the early 80s the MSX was a very respectable machine. Of course these were the days that superimposing graphics over a video was an amazing feat, but [Danjovic] and [Igor] are still having fun with their boxen. They designed a software interface for the Wii Nunchuck (translation) on their trusty MSX computer.

The plug coming out the back of a standard Wiimote is just a simple I2C bus. Many things can be done with this port from plugging in ancient controllers to controlling robots. [Danjovic] and [Igor] managed to write a routine in Basic that converts the I2C data coming out of the Nunchuck to data the MSX can understand without any modification of the hardware whatsoever.

All the guys needed to plug the Nunchuck into the MSX was a voltage divider and a few pull-up resistors between the computer and controller. They got data from both buttons, the joystick and the accelerometer in the Nunchuck and made a small program to display some sprites on the screen to demonstrate this. Check that out after the break.

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Programming AVR I2C Interface

January 9, 2012 by Kevin Dady 8 Comments

I²C as many of you know, is a simple serial interface for many peripheral devices to micro controllers, but it can quickly become confusing to people who may not be accustom to it. Because of that, I²C tutorials are always welcome, and this new tutorial by [Embedds] does an excellent job of how to use I ²C with an AVR with a 24C16 2Kbyte EEPROM.

The first half of the tutorial provides a clear explanation of how I²C works, including its signal structure, addressing, and data packets. It then moves on to AVR territory showing how to setup the I²C in an AtMega micro controller. The author uses a pretty standard to most of us Arduino, with software written in AVR C and a nifty little GUI programming application which eases the hassle of dealing with AVRDude directly.

Plenty of code samples follow from twiddling registers to a full blown application reading and writing bits from the EEPROM to a serial terminal on a PC.

I2C Level Converter

December 7, 2011 by Mike Szczys 23 Comments

You’ve got several devices which communicate via the I2C protocol, but some of them can only operate at 3.3V while the rest are hungry for a 5V connection. What to do? [Linux-works] built this I2C level converter to solve the problem.

The circuit comes from an NXP app note (PDF) on the issue. You can take a quick peek at the suggested schematic from that document. The design uses two MOSFETS for each side of the adaptor. Perhaps a better way to explain this is that you need one for the higher voltage and one for the lower voltage on each of the two data lines for a total of four parts. This allows for both of the buses to communicate as one, while still having their own 3.3V and 5V pull-up resistors.

[Linux-works] concedes that there are chips designed to do this for you, but he was able to source the BSS138 MOSFETs locally and for about ten cents a piece. Not a bad alternative to putting in a parts order.

FT-2232 Bridges Python And I2C/SPI

November 14, 2011 by Mike Szczys 9 Comments

You might already have the hardware on hand to easily interface I2C and SPI devices with Python scripts on your computer. The board seen above is an FT-2232 breakout board. These chips are often used to facilitate JTAG programming via USB, but they have other features that might be useful to you as well. The chip has a Multi-Protocol Synchronous Serial Engine (MPSSE) which can speak the I2C and SPI protocols, you just need to know how to active them in your code.

[Craig] makes this easy with his MPSSE Python wrapper. Simply install his module, and you’ll be able to import all the commands you need. He demonstrates reading the data out of a 1 MB SPI flash memory chip. This could be used for a lot more, including debugging peripherals à la the Bus Pirate, or reprogramming chips to add to your projects (we’re thinking font arrays and sprites for displays, or look-up tables).

If you’re not aware, these FTDI chips were the go-to for USB support for a long time. We’ve got a guide for bit-banging using this hardware. Lately more chips have become available with USB hardware built-in. They’re quite useful and cost-effective, especially with the availability of open-source stacks like the LUFA project.

Auxiliary Display For Beat707 Works Via I2C

July 26, 2011 by Mike Szczys 8 Comments

Bigtime is a simple way to create an auxiliary display for the Beat707 MIDI controller. The right half of the display shows the beat pattern that the drum machine is using, while the left half keeps track of the current measure.

Just a few components went into the extra hardware. A four-digit seven segment display is fed data from an ATtiny85. Since that microcontroller has only eight pins, a 595 shift register and CD4067 take care of translating serial data into the outputs necessary to light the display. The entire thing connects to the Beat707’s I2C bus, which means you don’t need to make hardware alterations to the original, and this leaves plenty of room for more addons.

The code package includes a Fritzing file, but for your convenience we’ve embedded a PNG of the hardware connections after the break. You’ll also find the demo video where [Guilherme] explains how this works.

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Working With I2C Port Expanders

June 7, 2011 by Mike Szczys 4 Comments

There are times when you don’t need much processing power for your project but you do need a lot of I/O pins. It often doesn’t make economic sense to choose a larger microcontroller just to get extra pins so the answer is to use a port expander chip. [Raendra] posted a guide for using one of these chips, it’s a Microchip MCP23008 chip that uses the I2C protocol for communications.

You are probably already familiar with using shift registers like the 595 series for port expansion. There can be benefits to using an I2C device instead. One of them comes when using multiple port expander chips. With cascading shift registers you must always shift in the data for the entire chain of chips. But I2C devices are individually addressable, so you only need to push data over the I2C bus for the chips that need to be changed, the others will remain unaffected. It is especially easy to use these if you already have another I2C device in your project design as the addition only requires the connection of the SDA and SCL lines. Keep them in mind for future undertakings.

I2C Arduino GPS Shield

May 24, 2011 by Mike Nathan 11 Comments

i2c_gps_shield

[Wayne] wrote in to share an item he just finished working on, an I²C GPS shield for the Arduino. While other GPS solutions have existed for quite some time, his caught our eye due to its feature list.

The shield removes a good bit of the hassle associated with parsing raw NMEA data from traditional GPS addons. While you have the option to communicate with the GPS module over serial in order to obtain the raw data, the use of the I²C interface makes getting the most commonly used GPS data a breeze. The GPS module itself can be set to update at anywhere from 1 to 10 Hz, and [Wayne] says that the I²C bus blows away the oft-used 9600 baud serial interface. While I²C is primarily used for receiving data, it can also be utilized to configure the GPS via its control registers, allowing for on the fly settings tweaks.

While he does sell the units pre-assembled at a competitive price, [Wayne] also provides a full schematic, making this an easy afternoon project once you have sourced the proper components.