Our friend [Garrett Mace] from macetech has finished a prototype of a new shield which allows the Arduino (or any other microcontroller with I2C) to add 64 digital I/O pins using only 2 of the analog pins. Currently he only has a few pre-production boards, and rather than selling them he is throwing a contest to win them. The contest is looking for people who have a specific project in mind that could use the centipede, and on Friday November 13th he will pick his favorite two. To submit an idea, just head over the Arduino forums and post an idea complete with details and relevant schematics, etc.

We will be sure to follow up with the winners of the contest, as well as let you all know when the Centipede Shield makes it into production.

Hackaday alum [Ian Lesnet] tipped us off about some reverse engineering of the HVR-1600, an analog and digital television encoder/tuner. The project was spawned when [Devin] noticed his Hauppauge HVR-1600 didn’t tune channels in Linux quite as well as it did in Windows. He had a hunch this was due to improper initialization settings for either the tuner chip or the demodulator.

To fix this he used two test points on the board to tap into the I2C bus. Using a logic analyzer he captured the command traffic from the bus while running Linux, then while running Windows. By filtering the results with a bit of Perl, and comparing them by using diff, he tracks down and finds the variation in the commands being sent by the two drivers. After a bit of poking around in the Linux source and making the necessary changes, he improved the tuning ability of the Linux package.

[Devin's] work looks simple enough, and it is. The difficult part of this process is being smart enough to know what you’re looking for, and what you’ve got once you’ve found it.

Macetech’s ChronoDot is a Real Time Clock module for projects requiring highly accurate time keeping and measurement. The ChronoDot uses the DS3231 chip, which features a TCXO to compensate for variations in temperature which affect normal oscillators, like the ones in most microcontrollers. The DS3231 uses simple I2C commands and registers for storing and retrieving time, but also features a variable output that goes all the way down to 1.000 hz for low power, interrupt style timekeeping applications. With the provided watch battery, the ChronoDot can keep time in idle mode for up to 8 years.

Normally the ChronoDot comes mostly assembled, requiring you to only solder on the watch battery. However, due to a manufacturing mistake, Macetech is selling a version with the header pins on the wrong side they call the ChronoDoh. This module is currently nearly half off the regular price of $14.99, which makes it a great low cost addition to a project. Macetech has sent us a couple of these modules to demonstrate how functional they still are.

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For months we’ve used our Bus Pirate universal serial interface tool to demonstrate electronics parts, so it’s only appropriate that the Bus Pirate get it’s own parts post. We recently had a Bus Pirate preorder, and today we received the pre-production Bus Pirate prototype from Seeed Studio. This prototype was mailed just a few days before preorder 1 started to ship, so those packages should start arriving any day.

Follow along as we unbox the prototype Bus Pirate, and connect it to a debugger to determine the PIC24FJ64GA002-I/SO revision that shipped with this board. Use this post to share your own Bus Pirate unboxing experience. Pictures and discussion after the break.

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[Marcus] has written up his experiences using the AD7746 capacitance sensor. He used the SparkFun breakout board in conjunction with an Arduino. The available Arduino code wasn’t that great so he rewrote it to be easier to understand. The AD7746 is an I2C device that can be continuously read, but this doesn’t mesh well with the Wiring libraries. Additionally, the calibration routine from the data sheet is difficult to understand. He’s included all of the code he used plus a Processing sketch to help visualize the input which will hopefully make your experience with the chip much more smooth.

The PCF8563 is a real-time clock/calendar/alarm chip with an I2C interface. This would be useful in projects where the primary microcontroller doesn’t have enough resources for an interrupt driven clock.

We demonstrate the PCF8563 using the Bus Pirate after the break. For a limited time you can get your own Bus Pirate, fully assembled and shipped worldwide, for only $30.

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Update, Saturday July 4th, 2009: All preorders are closed.

The Bus Pirate is a universal serial interface tool, we use it to test new chips without writing any code. It currently supports most serial protocols, including 1-Wire, I2C, SPI, JTAG, asynchronous serial, MIDI, and more. We added some other features we frequently need, like pulse-width modulation, frequency measurement, voltage measurement, bus sniffers, pull-up resistors, and switchable 3.3volt and 5volt power supplies.

The new v2 family adds USB power and connectivity to the best Bus Pirate design yet. We also reduced the part count and cost wherever possible. If you want to get your hands on some Bus Pirate USB goodness, Seeed Studio has assembled hardware for $30 (including worldwide shipping).

Read about the new design after the break.

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The DS1807 contains two logarithmic digital potentiometers (pots) for audio volume adjustment. Each pot has 64 volume levels plus a mute setting. The volume level of each pot is set over a two-wire I2C serial interface. We’ll show you how to connect and interface the DS1807 below.

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Linear Technology’s LTC2631A-LZ8 is an 8bit digital to analog converter (DAC) with an I2C interface. This DAC can output 255 different voltages, spaced evenly between 0 and 2.5volts. We previously demonstrated the LTC2640 with a three-wire SPI interface, but this version is controlled with only two signal wires.

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We use the Bus Pirate to interface a new chip without writing code or designing a PCB. Based on your feedback, and our experience using the original Bus Pirate to demonstrate various parts, we updated the design with new features and cheaper components.

There’s also a firmware update for both Bus Pirate hardware versions, with bug fixes, and a PC AT keyboard decoder. Check out the new Hack a Day Bus Pirate page, and browse the Bus Pirate source code in our Google code SVN repository.

We cover the design updates and interface a digital to analog converter below.

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