What is PWM?
Pulse-width Modulation
Go to https://github.com/sarfata/pi-blaster/
and Download.
Installing:
sudo apt-get install autoconf
Then unzip pi-blaster-master.zip and do:
./autogen.sh ./configure && make
To start pi-blaster and have it relaunched automatically on every reboot:
sudo make install
Afterwards it should look like this:
/etc/init.d/pi-blaster.boot.sh start
Using hardware: PWM
Number of channels: 8
PWM frequency: 100 Hz
PWM steps: 1000
Maximum period (100 %): 10000us
Minimum period (0.100%): 10us
How to use
Pi-Blaster creates a special FIFO file in /dev/pi-blaster. Any application on your Raspberry Pi can write to it (this means that only pi-blaster needs to be root, your application can run as a normal user).
Important: when using pi-blaster, the GPIO pins you send to it are configured as output.
To set the value of a PIN, you write a command to /dev/pi-blaster in the form <GPIOPinName>=<value> where <value> must be a number between 0 and 1 (included).
For a short example, this is how we set GPIO pin 17 to a PWM of 70%:
echo "17=0.7" > /dev/pi-blaster
I figured out which Gpio-ports are working for revision B:
GPIO number Pin in P1 header wPi numbers
4 P1-7 7
17 P1-11 0
18 P1-12 1
21 P1-13 2
22 P1-15 3
23 P1-16 4
24 P1-18 5
25 P1-22 6