Runs a python-uinput based joystick from IO Pi Plus i2c inputs
This project allows an AB Electronics IO Pi Plus Raspberry Pi expansion board (https://www.abelectronics.co.uk/p/54/IO-Pi-Plus) to be used to drive a python-uinput joystick.
The code currently supports a 1-Player and 2-Player joystick, but could easily be expanded to include more joysticks.
Refer to io_pi_plus_joystick/input_def.py for the IO Pi Plus pin - to - uinput joystick button mappings.
This project uses a submodule link to the AB Electronics UK IO Pi Python Library. To clone this project and the necessary submodule(s), use:
git clone --recursive https://github.com/csonsino/io_pi_plus_joystick.git
If you already cloned this repo without the "--recursive" argument, you can initialize the submodule(s) by running:
git submodule init
git submodule update
python-smbus
For Python 2.7:
sudo apt-get install python-smbus
For Python 3.4:
sudo apt-get install python3-smbus
I2C support enabled
sudo raspi-config
Select "Interfacing Options" -> "Enable I2C"
python-uinput
sudo apt-get install python-pip
sudo pip install python-uinput
Start the uinput kernel module:
sudo modprobe uinput
Optionally, add/create a modules.conf to autoload the uinput kernel module on boot:
sudo nano /etc/modules-load.d/modules.conf
Add the line:
uinput
Save the file and exit
To manually run a joystick:
- Use the run_joystick.sh script, supplying a "-p 1" argument for the Player 1 joystick, or a "-p 2" argument for the Player 2 joystick:
cd <io_pi_plus_joystick_dir>
./run_joystick.sh -p 1
- Run the python module directly:
cd <io_pi_plus_joystick_dir>
export PYTHONPATH=`pwd`:`pwd`/ABElectronics_Python_Libraries/IOPi:`pwd`/io_pi_plus_joystick
sudo python -m io_pi_plus_joystick.io_pi_plus_joystick -p <1_or_2>
To autoload a joystick using systemd, copy the included script(s) into the /lib/systemd/system/ directory:
Note - The scripts assume that you cloned this repository into /opt, if you cloned it into another location, you MUST update the .service scripts accordingly!
cd /opt/io_pi_plus_joystick
sudo cp ./systemd/io_pi_plus_joystick_1.service /lib/systemd/system/
sudo cp ./systemd/io_pi_plus_joystick_2.service /lib/systemd/system/
Start the service:
sudo systemctl start io_pi_plus_joystick_1.service
sudo systemctl start io_pi_plus_joystick_2.service
Enable the service on boot:
sudo systemctl enable io_pi_plus_joystick_1.service
sudo systemctl enable io_pi_plus_joystick_2.service
The easiest way to test the functionality of your joystick and this code is to use jstest:
Install the joystick tool kit:
sudo apt-get install joystick
Run jstest
For Player 1 Joystick, typically /dev/input/js0:
jstest /dev/input/js0
For Player 2 Joystick, typically /dev/input/js1:
jstest /dev/input/js1
The code currently uses a polling mechanism (see the Wishlist), and instead of using a single process with round-robin polling for all joysticks, I decided to run each joystick as a separate process. The thought is that a multiprocessor device could potentially handle the polling in parallel, thereby eliminating the round-robin delay for button processing on multiple joysticks. This might be a completely flawed thought process and for all I know it runs serially.
The polling interval is controlled by the BUTTON_POLL_S setting in io_pi_plus_joystick/input_def.py. There is a balance in trying to make this value as small as possible (to poll as quickly as possible, making the joystick more responsive), while still allowing the CPU to do other things (keeping the CPU utilization by the polling process as low as possible). On my Raspberry Pi 3 with the value of 0.007 (7 milliseconds between polling loops), I observe a typical CPU usage around 3.5-5% per joystick (under 10% for a 2-payer system). The joysticks and buttons seem to be very responsive, and it makes for a great playing experience on my custom built cabinet.
Ideally the joystick code should operate on an interrupt basis instead of the polling mechanism. Last I tried, I didn't have much luck using interrupts with the AB Electronics IO Pi Python library (the callbacks seemed to lock up with simultaneous button presses).