Pin

RPi.GPIO wrapper. Write code once, test it anywhere, run on Raspberry Pi

Why

I wanted to test some ideas I had in mind for my Raspberry Pi, but I didn't have it with me. So I made this really tiny library which acts as a wrapper for RPi.GPIO. You can write your code on your laptop, test it and then deploy it on your Raspberry Pi by only changing a value in a configuration file, only when it's really working.

How

First create a config file with this content:

{
  "test":true
}

This enables the mocking. If you're executing your script on a anctual raspberry you may want to set 'test' to false. This transforms every call to an actual GPIO call.

Now load your configuration file:

pin.config('/path/to/config/file')

Then you are ready to interact with the library exactly how you'd do with Rpi.GPIO:

pin.setmode(pin.BCM)
pin.setup(4,pin.OUT)
pin.output(4,pin.LOW)

The file and the call to config() are mandatory, since apparently RPi.GPIO can't be imported on a system that's not a Raspberry Pi. So the method also imports the module if the "test" value is false.

You may see a pin.conf dictionary and be tempted to set "test" there without an external file, and without calling config(). This way RPi.GPIO isn't imported and your code won't work on an actual Raspberry Pi. Use at your own risk.

What if you want your pin to read an input?

pin.setup(4,pin.IN)
value = pin.input(4)

This returns a random value. If you want to control the value read you can use pin.set_value():

# before starting your script
pin.set_value(4,0.5)
# your script
value = pin.input(4)

This way other applications can be built. For instance a GUI that simulates a Raspberry with devices attached.

Dependencies

You need to install RPi.GPIO for this to work https://sourceforge.net/p/raspberry-gpio-python/wiki/install/

In test mode this isn't required since RPi.GPIO isn't imported.

Tested under Python 3.6

Installation

Clone this repository, then run

python3 setup.py install

What's implemented of RPi.GPIO

• setup(channel,in_or_out,initial=pin.HIGH) same as GPIO, works also with a list of channels. Use pin.IN or pin.OUT, as well as pin.HIGH or pin.LOW
• setmode(mode) same as GPIO, use pin.BCM or pin.BOARD. In test mode this won't do anything.
• input(channel) same as GPIO, if pin.set_value(channel,value) isn't called before then a random number in range [0,1] is returned. Otherwise what you set with set_value() for that channel
• output(channel,value) same as GPIO, writes value to pin channel. In test mode you can retrieve what was set with pin.get_output(channel). You may use pin.HIGH or pin.LOW. As setup() works with a list of channels
• cleanup(channel) same as GPIO, works also with a list of channels

Additional functions

This functions are only useful in test mode. See `test` folder for better examples.

• set_value(channel,value) every time input(channel) is called, value is returned instead of a random number
• get_output(channel) returns whatever output(channel,value) wrote to channel

The future

People actually serious with their Raspberries, please let me know of improvement or whatever you may find useful. I use mine as an hobby, and I'm not an expert of IoT. Any contribution is welcomed basically.

Since I haven't found a way to properly and automatically test this library behaviour on a Rapsberry, either tell me how or report issues about the actual RPi.GPIO calls. What this library is trying to solve is exactly this apparent difficulty of testing Raspberry code properly.