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$805 pledged of $5,500 goal
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$805 pledged of $5,500 goal
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About this project

SPICE I2C Expansion Board

The SPICE I2C expansion board is a showcase design for I2C devices. It adds sensors, memory, display, I/O expander, etc. while only using two analog signals. 

The SPICE board does require 5 volts and ground for power.

This board is built to plug into an Arduino Uno. We included a standalone secondary 3.3 V power supply to control the low voltage devices. The board can be used with any microcontroller that supports I2C. This includes Raspberry Pi, PIC and other AVR microcontrollers, etc.



We have the following eight I2C devices on board:



1. Three Axis Accelerometer 
 

2. Four LED Driver (PWM for Dimming and/or Blinking)

3. EEPROM Memory - 32Kbit 


4. Digital Potentiometer - 5 kohm


5. RTCC, Real Time Clock/Calendar


6. 12-bit DAC 
(Digital to Analog Converter)

7. 16-bit I/O Expander 


8. Temperature Sensor 


Non-I2C Devices

1. Voltage Regulator & Level Shift, 3.3V 


2. Two (2) Seven-Segment Displays 


Hardware

Each I2C chip select represents a unique set of functions. For this reason we used chips from several manufacturers. SPICE I2C includes parts from NXP (formerly Philips the developer of the I2C protocol), Microchip, Texas Instruments, and Freescale. Each of these companies has areas of expertise that was leveraged to develop a board with a wide range of capabilities.

Software

Another major element of the development was software. In choosing a broad range of devices, we created a situation where controlling everything required unique software. Controlling a 16-bit I/O expander is different from setting the output on a digital potentiometer.

The most challenging was the accelerometer from Freescale. This device uses a repeat start operation that is not supported by the standard Wire library from Arduino. We found an alternate library from a great developer that does support this operation. That developer DSS Circuits has agreed to let us share their Arduino I2C library:

http://www.dsscircuits.com/articles/arduino-i2c-master-library.

For each device, we will have working sample code that will include comments to describe how the software works. This will give you a great starting point for developing code for your application.

Design Process

Because I2C devices are designed to work with a microcontroller, it is natural that most of them are small surface mounted devices (SMD). This created a development situation where straight forward breadboard alone would not work. We had to first mount the devices to breakout boards and then assemble them on a breadboard to test out the operation of the device.

Development on multiple breadboards.
Development on multiple breadboards.

That would have been difficult enough on its own, but we wanted to use parts that were designed for use in smartphones. These parts are extra small, and use tricky footprints. (You cannot find a breakout board for a DFN-8 device. There can be more than one style depending on size of the chip.) Custom designed and fabricated circuit boards were required to test the operation of some devices. 

This board was harder than it looks.
This board was harder than it looks.

These I2C devices are amazing with features like 3-axis accelerometer, temperature sensors, memory, expanders, etc. The small size and uncommon solder pads make them feel like they were designed to keep away hobbyist because they are difficult to solder. That made us more determined to open up opportunities for everyone to use them.

Did we mention that these parts are small? That meant the pad size and space between pads were small. Custom fabricated break out boards were going to push the boundaries of what we thought was possible. The prototype boards were not pretty, but they allowed us to verify we could use these parts before we built an expansion board around them.

These parts are small!!
These parts are small!!

We learned the difficulty in soldering these devices, difficult but possible with determination. For some of these devices, the soldering pads are on the bottom of the chip with no external leads.

We did most of the soldering using hot air oven re-flow, but then we had to use hand soldering to fix solder bridges. It felt like an impossible task when we first tried fixing a solder bridge under the chip.

Some parts were too small to fabricate in-house PCB. The pads were too close together, e.g. QFN-16 parts had too many leads on too small a package. For these we designed breakout boards for commercial PCB fabrication. These were made at the same time as the fully designed expansion board. The plan was to test the final few parts, and at the same time be ready with a fully designed expansion board.

This was a risk, but there was simply no way to fabricate them with our equipment.

Features

Hardware and software are only part of our development efforts. Integration was an element in the selection process. We included components that operate both at 5V and at 3.3V. This requires not only a second voltage, but also level conversion for the I2C communication signals.

3.3V Power and Level Shift Included.
3.3V Power and Level Shift Included.

While the Arduino board can provide the 3.3 volts, we built in the capability  into the expansion board. The SPICE board can be used standalone with most other microcontrollers that have I2C capabilities.

The I2C protocol allows for all the devices on the expansion board to be controlled with only two wires. That is eight I2C devices using just two wires for control and another two wires to provide 5V and ground. You can connect even more external I2C devices using the same two analog signals.

Add more.
Add more.


Special Reward

We had fun working with all the different SMD parts, so we designed a souvenir board based on the development breakout boards. Each side of the souvenir board has a different SMD layouts for many wiring possibilities.

Top Side - Souvenier Board
Top Side - Souvenier Board
Bottom Side - Souvenier Board
Bottom Side - Souvenier Board

Stretch Goals

Previously all of our projects have been launched as assembled and DIY. That is because we believe that by building it yourself, you will be empowered to take on greater challenges.

This project is at the very edge of DIY. After we raise enough funds to cover the minimum assembly cost, we will begin offering this as a DIY kit. This will be an advanced level kit, not recommended for beginners. See our store website http://www.jouletime.com/store.html for beginner or intermediate level kits.

Shipping

We do ship internationally. If you don't see your country listed, contact us for a estimate for shipping. Our international shipping is usually USPS first class without tracking.

Risks and challenges

We have successfully launched two Kickstarter campaigns. Each was more complex and difficult to assemble. This is the most complex and challenging project we have attempted.

Because of these complexities, this project has the highest initial launch cost of any of our projects. We have to reach this goal to make this project cost effective.

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  1. Select this reward

    Pledge $1 or more About $1.00

    Supporter

    Thank you for supporting our campaign. You will get access to all of our updates and you name posted to our website.

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    Pledge $5 or more About $5

    Project Supporter - Development Board

    We will have a limited number of prototype boards (no additional parts). We cannot use them for production, but they would make a good challenge or drink coaster.

    We may substitute a production board if we run out of prototype boards.

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    Pledge $10 or more About $10

    Project Supporter - Souvenir PCB Board

    If you like this project, but are not interested in all the devices, then here is a small token of appreciation for your support. You will receive a bare printed circuit board (no additional parts).

    This board is a giant break out board with many of the SMD footprints used in the SPICE board.

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    Pledge $49 or more About $49

    Early Bird Special - Partially-Assembled SPICE I2C, expansion board.

    These boards will not have any of the headers soldered on the boards. You can use the ones we send or substitute whatever you like.

    This will include one set of headers. All the SMD parts will be soldered before shipping.

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  5. Select this reward

    Pledge $54 or more About $54

    Some Assembly Required - Partially-Assembled SPICE I2C, expansion board.

    These boards will not have any of the headers soldered on the boards. You can use the ones we send or substitute whatever you like.

    This will include one set of headers. All the SMD parts will be soldered before shipping.

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    Pledge $59 or more About $59

    Assembled Spectrum I2C, expansion board.

    This is a fully assembled and working SPICE I2C expansion board.

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  7. Select this reward

    Pledge $60 or more About $60

    Early Bird Special - Partially-Assembled SPICE I2C, expansion board.

    These boards will not have any of the headers soldered on the boards. You can use the ones we send or substitute whatever you like.

    This will include one set of headers. All the SMD parts will be soldered before shipping.

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    Ships to Anywhere in the world
    Limited 2 backers
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  8. Select this reward

    Pledge $70 or more About $70

    Assembled Spectrum I2C, expansion board.

    This is a fully assembled and working SPICE I2C expansion board.

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    Ships to Anywhere in the world
    3 backers
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Funding period

- (32 days)