SparkFun Blocks for Intel® Edison - Pi Block

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Contributors: Shawn Hymel
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Using the Pi Block

To use the Pi Block, attach an Intel® Edison to the back of the board, or add it to your current stack. Blocks can be stacked without hardware, but it leaves the expansion connectors unprotected from mechanical stress.

Edison installed on Pi Block

Edison installed on Pi Block

We have a nice Hardware Pack available that gives enough hardware to secure three blocks and an Edison.

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NOTE: It is recommended to use a console communication block in conjunction with this block like ones found in the General Guide to Sparkfun Blocks for Intel Edison. Once you have the Edison configured, you can remove the console communication block, power the Edison from the Pi Block, and SSH into the Edison.

You can put headers on the Edison side, which gives you easy access to the pin labels. Note that this pinout is mirrored from the Raspberry Pi Model B pinout.

Headers on top of Edison Pi Block

Headers on Edison side

Alternatively, you can populate the back side of the Pi Block with headers. This method gives the same pinout as a Raspberry Pi Model B. You could, in theory, swap the Edison in for your Raspberry Pi on an existing project, or use Raspberry Pi accessories (e.g. Pi Wedge).

Headers on bottom of Edison Pi Block

Or put headers on the back side of Pi Block

Using the Pi Block as an output device

If you want to use the Pi Block to control high power LEDs or relays, an external transistor or MOSFET will be required. It is possible to illuminate a small LED directly from the level shifter. It may not be as bright since the current output of the TXB0108 level converter is very low (~5ma).

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Connection Diagram for Load (LED, Motor, or Relay)

In the terminal, we will demonstrate how to activate and use a GPIO pin as an output.

First navigate to the GPIO directory on the Edison.

cd /sys/class/gpio

Select the GPIO pin to enable. In this case, we used GPIO 14, which is labeled "GP14" on the Pi Block.

echo 14 > export

Navigate to the newly created GPIO directory.

cd gpio14

If you type "ls", you should see a bunch of variables.

active_low  direction   power       uevent
device      edge        subsystem   value

Let's set the "direction" of the port to output

echo out > direction

To confirm this, we will "cat" the value

cat direction

You should see the "out" in the command line. Now the device is configured as an output. "value" is where the status of the pin is set, 1 for high, 0 for low.

echo 1 > value

Testing with a multi-meter, small led, or oscilloscope, you should see a "high" status (3.3V) present on gpio14.

Using the Pi Block as an input device

If you want the Pi Block to read switches, buttons, or other logic level inputs, you must pay attention to pull-up and pull-down resistors. The level converter on board is very weak. Here are two scenarios explained:

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Connection Diagram for Active High Push Button

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Connection Diagram for Active Low Push Button

In the terminal, we will demonstrate how to activate and use a GPIO pin as an input configured as an active high.

First, navigate to the GPIO directory on the Edison.

cd /sys/class/gpio

Select the GPIO pin to enable. In this case let us use GPIO 14.

echo 14 > export

Navigate to the newly created GPIO directory.

cd gpio14

If you type "ls", you should see a bunch of variables.

active_low  direction   power       uevent
device      edge        subsystem   value

Let's set the "direction" of the port to output.

echo in > direction

To confirm this, we will "cat" the value.

cat direction

You should see the "in" in the command line. Now the device is configured as an input. "value" is where the status of the pin is set, 1 for high, 0 for low.

cat value

With a button pressed, you should see a 1. When the button is not pressed you should see a 0. Using the up arrow, you can recall previously run commands.