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Description:

SimulRPi 0.1.0a1

SimulRPi is a library that partly fakes
RPi.GPIO and simulates some I/O devices
on a Raspberry Pi (RPi).
Example: simulating LEDs connected to an RPi via a terminal

Introduction
Dependencies
Installation instructions 😎
Usage

Use the library in your own code

Case 1: with a try and except blocks
Case 2: with a simulation flag

Script run_examples

List of options
How to run the script

Examples

Example 1: display 1 LED
Example 2: display 3 LEDs
Example 3: detect a pressed key
Example 4: blink a LED
Example 5: blink a LED if a key is pressed

How to uninstall 😞
Resources
References

Introduction
In addition to partly faking RPi.GPIO, SimulRPi also simulates these I/O
devices connected to an RPi:

push buttons by listening to pressed keyboard keys and
LEDs by blinking dots in the terminal along with their GPIO pin
numbers.

When a LED is turned on, it is shown as a red dot in the terminal. The
pynput package is used to monitor the keyboard for any pressed key. Thus,
the SimulRPi library can be useful in the case that you want to try your
RPi.GPIO-based script by running it on your computer when no RPi is
available at the moment.
Example: terminal output

Each dot represents a blinking LED connected to an RPi and the number
between brackets is the associated GPIO channel number. Here the LED on
channel 22 toggles between on and off when a key is pressed.
Also, the color of the LEDs can be customized as you can see here where the LED
on channel 22 is colored differently from the others.
Important

This library is not a Raspberry Pi emulator nor a complete mock-up of
RPi.GPIO, only the most important functions that I needed for my
Darth-Vader-RPi project were added.
If there is enough interest in this library, I will eventually mock more
functions from RPi.GPIO.

Dependencies

Platforms: Linux, macOS
Python: 3.5, 3.6, 3.7, 3.8
pynput >=1.6.8: for monitoring the keyboard for any pressed key

Installation instructions 😎

Make sure to update pip:
$ pip install --upgrade pip

Install the package SimulRPi with pip:
$ pip install SimulRPi
It will install the dependency pynput if it is not already found in your
system.

Important

Make sure that pip is working with the correct Python version. It might be
the case that pip is using Python 2.x You can find what Python version
pip uses with the following:
$ pip -V
If pip is working with the wrong Python version, then try to use pip3
which works with Python 3.x

Note

To install the bleeding-edge version of the SimulRPi package,
install it from its github repository:
$ pip install git+https://github.com/raul23/SimulRPi#egg=SimulRPi
However, this latest version is not as stable as the one from
PyPI but you get the latest features being implemented.

Warning message
If you get the warning message from pip that the run_examples script
is not defined in your PATH:
WARNING: The script run_examples is installed in '/home/pi/.local/bin' which is not on PATH.
Add the directory mentioned in the warning to your PATH by editing your
configuration file (e.g. .bashrc). See this article on how to set PATH
on Linux and macOS.
Test installation
Test your installation by importing SimulRPi and printing its version:
$ python -c "import SimulRPi; print(SimulRPi.__version__)"

Usage

Use the library in your own code

Case 1: with a try and except blocks
You can try importing RPi.GPIO first and if it is not found, then fallback
on the SimulRPi.GPIO module.
try:
import RPi.GPIO as GPIO
except ImportError:
import SimulRPi.GPIO as GPIO

# Rest of your code
The code from the previous example would be put at the beginning of your file
with the other imports.

Case 2: with a simulation flag
Or maybe you have a flag to tell whether you want to work with the simulation
module or the real one.
if simulation:
import SimulRPi.GPIO as GPIO
else:
import RPi.GPIO as GPIO

# Rest of your code

Script run_examples
The run_examples script which you have access to once you install
the SimulRPi package allows you to run different code examples on your RPi
or computer. If it is run on your computer, it will make use of the
SimulRPi.GPIO module which partly fakes RPi.GPIO.
The different code examples are those presented in Examples and show the
capability of SimulRPi.GPIO for simulating I/O devices on an RPi such as
push buttons and LEDs.

Here is a list of the functions that implement each code example:

Example 1: ex1_turn_on_led()
Example 2: ex2_turn_on_many_leds()
Example 3: ex3_detect_button()
Example 4: ex4_blink_led()
Example 5: ex5_blink_led_if_button()

List of options
To display the script’s list of options and their descriptions:
$ run_examples -h

-e
The number of the code example you want to run. It is required.
(default: None)

-m
Set the numbering system (BCM or BOARD) used to identify the I/O pins
on an RPi. (default: BCM)

-s
Enable simulation mode, i.e. SimulRPi.GPIO will be used for
simulating RPi.GPIO. (default: False)

-l
The channel numbers to be used for LEDs. If an example only
requires 1 channel, the first channel from the provided list will
be used. (default: [9, 10, 11])

-b
The channel number to be used for a push button. The default value
is channel 17 which is associated by default with the keyboard key
cmd_r. (default: 17)

-k
The name of the key associated with the button channel. The name
must be one of those recognized by the pynput package. See the
SimulRPi documentation for a list of valid key names:
https://bit.ly/2Pw1OBe. Example: alt, ctrl_r (default: cmd_r)

-t
Total time in seconds the LEDs will be blinking. (default: 4)

--on
Time in seconds the LEDs will stay turned ON at a time. (default: 1)

--off
Time in seconds the LEDs will stay turned OFF at a time. (default: 1)

-a
Use ASCII-based LED symbols. Useful if you are having problems
displaying the default LED signs that make use of special characters.
However, it is recommended to fix your display problems which might be
caused by locale settings not set correctly. Check the article
‘Display problems’ @ https://bit.ly/35B8bfs for more info about
solutions to display problems (default: False)

How to run the script
Once you install the SimulRPi package, you should have access to the
run_examples script which can be called from the terminal by providing some
arguments.
For example:
$ run_examples -e 1 -s
Let’s run the code example 5 which blinks a LED if a specified key is
pressed:
$ run_examples -s -e 5 -l 22 -t 5 -k ctrl_r
Explanation of the previous command-line:

-s: we run the code example as a simulation, i.e. on our computer
instead of an RPi
-e 5: we run code example 5 which blinks a LED if a key is pressed
-l 22: we blink a LED on channel 22
-t 5: we blink a LED for a total of 5 seconds
-k ctrl_r: a LED is blinked if the key ctrl_r is pressed

Output:

Important

Don’t forget the -s flag when running the run_examples script as simulation,
if you want to run a code example on your computer, and not on your RPi.

Examples
The examples presented thereafter will show you how to use SimulRPi to
simulate LEDs and push buttons.
The code for the examples shown here can be also found as a script in
run_examples.
Note

Since we are showing how to use the SimulRPi package, the presented code
examples are to be executed on your computer. However, the
run_examples script which runs the following code examples can be executed on a
Raspberry Pi or your computer.

Example 1: display 1 LED
Example 1 consists in displaying one LED on the GPIO channel 10. Here is
the code along with the output from the terminal:
import SimulRPi.GPIO as GPIO

led_channel = 10
GPIO.setmode(GPIO.BCM)
GPIO.setup(led_channel, GPIO.OUT)
GPIO.output(led_channel, GPIO.HIGH)
GPIO.cleanup()
Output:

The command line for reproducing the same results for example 1 with the
run_examples script is the following:
$ run_examples -s -e 1 -l 10
Warning

Always call GPIO.cleanup() at the end of your program to free up any
resources such as stopping threads.

Example 2: display 3 LEDs
Example 2 consists in displaying three LEDs on channels 9, 10, and 11,
respectively. Here is the code along with the output from the terminal:
import SimulRPi.GPIO as GPIO

led_channels = [9, 10, 11]
GPIO.setmode(GPIO.BCM)
GPIO.setup(led_channels, GPIO.OUT)
GPIO.output(led_channels, GPIO.HIGH)
GPIO.cleanup()
Output:

The command line for reproducing the same results for example 2 with the
run_examples script is the following:
$ run_examples -s -e 2
Note

In example 2, we could have also used a for loop to setup the output
channels and set their states (but more cumbersome):
import SimulRPi.GPIO as GPIO

led_channels = [9, 10, 11]
GPIO.setmode(GPIO.BCM)
for ch in led_channels:
GPIO.setup(ch, GPIO.OUT)
GPIO.output(ch, GPIO.HIGH)
GPIO.cleanup()
The GPIO.setup() function accepts channel numbers as int, list,
and tuple. Same with the GPIO.output() function which also accepts
channel numbers and output states as int, list, and tuple.

Example 3: detect a pressed key
Example 3 consists in detecting if the key cmd_r is pressed and then
printing a message. Here is the code along with the output from the terminal:
import SimulRPi.GPIO as GPIO

channel = 17
GPIO.setmode(GPIO.BCM)
GPIO.setup(channel, GPIO.IN, pull_up_down=GPIO.PUD_UP)
print("Press key 'cmd_r' to exit\n")
while True:
if not GPIO.input(channel):
print("Key pressed!")
break
GPIO.cleanup()
Output:

The command line for reproducing the same results for example 3 with the
run_examples script is the following:
$ run_examples -s -e 3 -k cmd_r
Note

By default, SimulRPi maps the key cmd_r to channel 17 as can be
seen from the default key-to-channel map.
See also the documentation for SimulRPi.mapping where the default keymap
is defined.

Example 4: blink a LED
Example 4 consists in blinking a LED on channel 22 for 4 seconds (or until
you press ctrl + c). Here is the code along with the output from
the terminal:
import time
import SimulRPi.GPIO as GPIO

channel = 22
GPIO.setmode(GPIO.BCM)
GPIO.setup(channel, GPIO.OUT)
start = time.time()
print("Ex 4: blink a LED for 4.0 seconds\n")
while (time.time() - start) < 4:
try:
GPIO.output(channel, GPIO.HIGH)
time.sleep(0.5)
GPIO.output(channel, GPIO.LOW)
time.sleep(0.5)
except KeyboardInterrupt:
break
GPIO.cleanup()
Output:

The command line for reproducing the same results for example 4 with the
run_examples script is the following:
$ run_examples -s -e 4 -t 4 -l 22

Example 5: blink a LED if a key is pressed
Example 5 consists in blinking a LED on channel 10 for 3 seconds if the key
shift_r is pressed. And then exiting from the program. The program can
also be terminated at anytime by pressing ctrl + c. Here is the code
along with the output from the terminal:
import time
import SimulRPi.GPIO as GPIO

led_channel = 10
key_channel = 27
GPIO.setmode(GPIO.BCM)
GPIO.setup(led_channel, GPIO.OUT)
GPIO.setup(key_channel, GPIO.IN, pull_up_down=GPIO.PUD_UP)
print("Press the key 'shift_r' to turn on light ...\n")
while True:
try:
if not GPIO.input(key_channel):
print("The key 'shift_r' was pressed!")
start = time.time()
while (time.time() - start) < 3:
GPIO.output(led_channel, GPIO.HIGH)
time.sleep(0.5)
GPIO.output(led_channel, GPIO.LOW)
time.sleep(0.5)
break
except KeyboardInterrupt:
break
GPIO.cleanup()
Output:

The command line for reproducing the same results for example 5 with the
run_examples script is the following:
$ run_examples -s -e 5 -t 3 -l 10 -b 27
Note

By default, SimulRPi maps the key shift_r to channel 27 as can be
seen from the default key-to-channel map.
See also the documentation for SimulRPi.mapping where the default keymap
is defined.

How to uninstall 😞
To uninstall only the package SimulRPi:
$ pip uninstall simulrpi
To uninstall the package SimulRPi and its dependency:
$ pip uninstall simulrpi pynput

Resources

SimulRPi documentation
SimulRPi Changelog
SimulRPi GitHub: source code
Darth-Vader-RPi: personal project using RPi.GPIO for activating a Darth
Vader action figure with light and sounds and SimulRPi.GPIO as fallback if
testing on a computer when no RPi is available

References

pynput: package used for monitoring the keyboard for any pressed key as to
simulate push buttons connected to an RPi
RPi.GPIO: a module to control RPi GPIO channels