As featured on Hackaday! This project for the Raspberry Pi uses cheap HC-SR04 ultrasonic sensors as inputs and turns them into keys on a MIDI keyboard. There's something pretty neat about using sound to make sound. It's like fighting fire with fire, but much safer.
There is a detailed instructable with full information on how to make this project.
To have the code start up when you boot the Raspberry Pi (without needing keyboard, mouse, and monitor attached) add these lines to your /etc/rc.local file and reboot.
. /home/pi/.cargo/env
cd /home/pi/UltrasonicPiPiano
./run.sh > /var/log/ultrasonic-pi.log 2>&1
In my case, the full /etc/rc.local file looked like this after adding those lines:
#!/bin/sh -e
#
# rc.local
#
# This script is executed at the end of each multiuser runlevel.
# Make sure that the script will "exit 0" on success or any other
# value on error.
#
# In order to enable or disable this script just change the execution
# bits.
#
# By default this script does nothing.
# Print the IP address
_IP=$(hostname -I) || true
if [ "$_IP" ]; then
printf "My IP address is %s\n" "$_IP"
fi
. /home/pi/.cargo/env
cd /home/pi/UltrasonicPiPiano
./run.sh > /var/log/ultrasonic-pi.log 2>&1
exit 0
If the code doesn't start running on bootup, check the log at /var/log/ultrasonic-pi.log for error messages.
To stop the program from running in the background, run the following command:
sudo killall -9 ultrasonic_piano