Hardware in 2016

Oh Eye: Analog Inputs for Raspberry Pi

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It isn’t an IO Board, it’s an “Oh Eye” board: sixteen 10-bit analog inputs and 8 digital inputs/outputs pulled out. It makes it easier to use the Pi as part of a special purpose appliance or musical instrument. The analog inputs are via two MCP3008 chips connected to the Raspberry Pi’s hardware SPI interface. The use of this ADC chip with the Pi is common and well documented. You may ask: “isn’t 16 channels of analog input a little overkill?” To which I would answer: yes it is, except when it isn’t.

There’s also a version for the Raspberry Pi Zero (will fit any post-Model B Raspberry Pi).

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The Oh Eye Zero for Raspberry Pi Zero is a more minimal board that will fit any post-Model B Pi boards.

A Mess of Inputs

Once you’ve done a number of projects with a lot of potentiometers or analog sensors you’ll appreciate the handiness of the convenience headers. When you’re using analog inputs you are always running three wires to everything: power, ground, and signal.

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Attach up to 16 analog sensors like this accelerometer (left) or 8 digital inputs like this button (right).

The convenience header makes it easy to use three-wire servo cables. With these cables you get a nice solid connection that isn’t going to break at the joint over time, and you can disconnect your panel of pots when you need to. No more stripping dozens of connections (although you can still do that if you like).

A Few More Features

If you’re hooking up buttons or switches to the Pi you’ll always need a connection to ground (or power) as well, so the Oh Eye pulls out 8 digital pins with a ground rail as well. On the digital inputs, you almost always need a pullup resistor. The Raspberry Pi has internal pullups but they are weak (in the 50k range) and may be susceptible to noise. If you need a smaller value, the Oh Eye has neat pads and holes for adding through hole, SMT or a network of resistors for all your pullup needs.

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It also has an six pin header (aka “FTDI header”) that allows you to connect to the Pi’s serial port via a 3.3V USB BUB or FTDI Friend. And an I2C header with power and ground, which is handy.

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