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SparkFun Blocks for Intel® Edison - Pi Block
Introduction
The Pi Block breaks out and level shifts several GPIO pins from the Intel
Edison. It presents them in the same configuration as a Raspberry Pi Model
B.
Pi Block
Suggested Reading
If you are unfamiliar with Blocks, take a look at the General Guide to
Sparkfun Blocks for Intel Edison.
Other tutorials that may help you on your Edison adventure include:
• Edison Getting Started Guide
• Logic Levels
Board Overview
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Pi Block Functional Diagram
• USB Power - used to provide 5V to Pi Block and power the Edison.
Note that the data lines are not connected to the Edison.
• Power Button - The power switch is connected to the “PWRBTN” line
on the Edison. This give the user the ability to place an Edison in
sleep or power down the module completely. This does not affect
power to other Blocks in the stack.
• Power LED - The power LED illuminates when power is present on
VSYS. This can come from the onboard USB Power or any other
powered Block in the stack.
• Expansion Header - The 70-pin Expansion header breaks out the
functionality of the Intel Edison. This header also passes signals and
power throughout the stack. These function much like an Arduino
Shield.
• LED Jumper - If power consumption is an issue, cut this jumper to
disable the power LED.
• VSYS Jumper - By default, a USB cable must be attached to the
USB Power port to provide power to the 5V pins on the RPi B
Header. You can power the Edison and Pi Block from another Block
(e.g. Base Block), but there will not be 5V on the pins labeled “5V”.
By closing this jumper, you can power the Edison and Pi Block from
another Block, and ~4.2V (VSYS) will appear on the pins labeled
“5V”.
• RPi B Header - Same configuration as the old Raspberry Pi Model B
pinout.
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.
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Edison installed on Pi Block
We have a nice Hardware Pack available that gives enough hardware to
secure three blocks and an Edison.
Intel Edison Hardware Pack
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 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).
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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).
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.
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active_low
device
direction
edge
power
subsystem
uevent
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:
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.
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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.
C++ Examples
We’re assuming that you’re using the Eclipse IDE as detailed in our Beyond
Arduino tutorial. If you aren’t, you’ll need to go to that tutorial to get up to
speed.
Hardware Connection
Hardware support for this library is simple; one basic red LED and one
momentary pushbutton. We’re using a 2N3904 NPN transistor to drive the
LED, however, as the drive strength of the outputs on the Pi Block is quite
weak. As you can see in the diagram, you’ll also need a couple of 1kΩ
resistors and a single 330Ω resistor.
While we’ve used GPIO45 and GPIO46 in this example, this code can be
used with any of the pins on the Pi breakout. The GPIO to MRAA pin map
can be found in the Resources and Going Further section.
Code
Follow the instructions in the programming tutorial to create a new project
named “SparkFun_Pi_Block_Example”. Once you’ve created the project,
open the “SparkFun_Pi_Block_Example.cpp” file and replace all the
existing code with the code block below.
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/***********************************************************
*****
Example file for SparkFun Pi Block Support
14 Jul 2015 Mike Hord, SparkFun Electronics
Code developed in Intel's Eclipse IOTDK
Modified on July 30, 2015 by Shawn Hymel, SparkFun Electroni
cs
This code requires the Intel mraa library to function; for m
ore
information see https://github.com/inteliotdevkit/mraa
This code is beerware; if you use it, please buy me (or any
other
SparkFun employee) a cold beverage next time you run into on
e of
us at the local.
************************************************************
****/
#include "mraa.hpp"
#include
#include
using namespace mraa;
using namespace std;
int main()
{
// Oddly, GPIO pin assignment numbers when using the MRAA li
braries are not
// the same as those inside the operating system. Thus, whi
le we're using
// pin 46 as far as the OS is concerned to drive the LED, w
e're using pin 32
// as far as MRAA is concerned. The cheat sheet for that ca
n be found here:
// https://github.com/inteliotdevkit/mraa/blob/master/doc
s/edison.md
Gpio LEDPin(45);
LEDPin.dir(DIR_OUT);
// Now do a quick little flicker.
LEDPin.write(0);
usleep(100000);
LEDPin.write(1);
usleep(100000);
LEDPin.write(0);
// Alternatively, we can declare the pin in "raw" mode, whic
h has a slightly
// different and more unwieldy constructor.
Gpio buttonPin(32, true, true);
buttonPin.dir(DIR_IN);
// In this infinite loop, we'll blink the LED once whenever
someone presses
// the button.
while (1)
{
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// We *know* that if the IO pin reads as 0, or is low, rea
d() returns zero.
// However, if it's high, it *may* return something els
e; the only guarantee
// is that it will be nonzero. Thus, don't test to see i
f a read() returned
// a 1!!!
if (buttonPin.read() == 0)
{
LEDPin.write(1);
sleep(1);
LEDPin.write(0);
sleep(1);
}
}
return MRAA_SUCCESS;
}
Additional Examples
Because this block is just a GPIO access device, the existing MRAA GPIO
examples can be used with it.
Example projects in the IDE
When you create a new project in the Eclipse IDE, it will offer you the option
of several starter projects. Some of them, noted above, are good examples
of using the MRAA GPIO functions. They’re more complex than what we’ve
provided here, however.
For full documentation of the C++ API for GPIO pins, please visit the official
MRAA documentation.
Resources and Going Further
Pin Map
You might have noticed that we used GP46 in hardware and GPIO 32 in
our example code. This is because the MRAA library uses a different
number for the pins. If you would like to use MRAA to control hardware,
figure out which GPIO pins you plan to use on the table below (labeled
“Edison Pin”) and then use the MRAA Number in software.
The available pins on the Pi Block have been highlighted in yellow in the
table.
Notes:
•
•
•
•
Input/output voltage on the Pi Block is 3.3V
Input/output voltage on the GPIO Block is 3.3V by default
Input/output voltage on the Arduino Breakout is 5V
Input/output voltage on the Mini Breadboard is 1.8V
MRAA pin map table based on Intel’s IOT Dev Kit Repository
Edison
Pin
(Linux)
Arduino
Breakout
Mini
Breakout
GP12
3
J18-7
GP13
5
GP14
A4
MRAA
Number
Pinmode0
Pinmode1
20
GPIO-12
PWM0
J18-1
14
GPIO-13
PWM1
J19-9
36
GPIO-14
Pinmode2
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Edison
Pin
(Linux)
Arduino
Breakout
Mini
Breakout
MRAA
Number
Pinmode0
Pinmode1
GP15
J20-7
48
GPIO-15
GP19
J18-6
19
GPIO-19
I2C-1-SCL
GP20
J17-8
7
GPIO-20
I2C-1-SDA
GP27
J17-7
6
GPIO-27
I2C-6-SCL
GP28
J17-9
8
GPIO-28
I2C-6-SDA
GP40
13
J19-10
37
GPIO-40
SSP2_CLK
GP41
10
J20-10
51
GPIO-41
SSP2_FS
GP42
12
J20-9
50
GPIO-42
SSP2_RXD
GP43
11
J19-11
38
GPIO-43
SSP2_TXD
GP44
A0
J19-4
31
GPIO-44
GP45
A1
J20-4
45
GPIO-45
GP46
A2
J19-5
32
GPIO-46
GP47
A3
J20-5
46
GPIO-47
GP48
7
J19-6
33
GPIO-48
GP49
8
J20-6
47
GPIO-49
GP77
J19-12
39
GPIO-77
SD
GP78
J20-11
52
GPIO-78
SD
GP79
J20-12
53
GPIO-79
SD
GP80
J20-13
54
GPIO-80
SD
GP81
J20-14
55
GPIO-81
SD
GP82
J19-13
40
GPIO-82
SD
GP83
J19-14
41
GPIO-83
SD
GP84
J20-8
49
GPIO-84
SD
GP109
J17-11
10
GPIO-109
SPI-5-SCK
GP110
J18-10
23
GPIO-110
SPI-5-CS0
GP111
J17-10
9
GPIO-111
SPI-5-CS1
GP114
J18-11
24
GPIO-114
SPI-5MISO
GP115
J17-12
11
GPIO-115
SPI-5MOSI
J17-14
13
GPIO-128
UART-1CTS
GP128
2
Pinmode2
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Edison
Pin
(Linux)
Arduino
Breakout
Mini
Breakout
GP129
4
GP130
GP131
MRAA
Number
Pinmode0
Pinmode1
J18-12
25
GPIO-129
UART-1RTS
0
J18-13
26
GPIO-130
UART-1RX
1
J19-8
35
GPIO-131
UART-1-TX
GP134
J20-3
44
GP135
J17-5
4
GPIO-135
UART
GP165
A5
J18-2
15
GPIO-165
GP182
6
J17-1
0
GPIO-182
PWM2
GP183
9
J18-8
21
GPIO-183
PWM3
Pinmode2
Edison General Topics:
• General Guide to Sparkfun Blocks for Intel Edison
• Edison Getting Started Guide - Programming with Arduino
• Loading Debian (Ubilinix) on the Edison
Block Specific Topics:
• Pi Block Github repo
Check out these other Edison related tutorials from SparkFun:
SparkFun Blocks for Intel®
Edison - OLED Block
SparkFun Blocks for Intel®
Edison - Dual H-Bridge
A quick overview of the features of
the OLED Block for the Edison.
A quick overview of the features of
the Dual H-bridge Block.
Programming the Intel®
Edison: Beyond the Arduino
IDE
SparkFun Blocks for Intel®
Edison - ADC V20
Intel's Edison module goes beyond
being just another Arduino clone.
Check this tutorial for advice on how
to get the most out of your Edison
by writing code in C++!
A quick overview of the features of
the ADC Block.
https://learn.sparkfun.com/tutorials/sparkfun-blocks-for-intel-edison---pi-block?_ga=1.23... 10/12/2015
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