What is it?

Raspberry Pi audio hat with 40-pin header, which uses the PWM0 and PWM1 Raspberry PI outputs to produce a sound. It works with the GPIO12 and GPIO13 outputs of the Raspberry Pi. A headphone or audio cable can be connected to an 3.5mm mm audio jack. On the board is embedded also stereo audio amplifier at which outputs can be connected speakers. Their impedance can be in the range 4-8 Ohm. The maximum possible power is 3W. The volume can be regulated by the use of potentiometer. The audio power amplifier can be switched off by the use of micro slide switch.

Why did you make it?

Some models Raspberry Pi does not have direct audio output. The audio can be extracted from the HDMI output but this reqires bulky external devices, which can be quite expensive. An USB audio cards can be used also, but they require also the use of USB hub and they are not always compatible with the OS. The designed by me audio hat solves these problems.

What makes it special?

It works with the GPIO12 and GPIO13 outputs of the Raspberry Pi configured as PWM0 and PWM1 outputs.

Here is the procedure to make this possible:

• run sudo raspi-config
• go to "Advanced options"
• chose "Audio"
• select "Force 3.5mm (Headphone) jack"

You also have to add the following line at the bottom of the "/boot/config.txt" : dtoverlay=pwm-2chan,pin=12,func=4,pin2=13,func2=4

You can test the sound with the command : aplay /usr/share/sounds/alsa/Front_Center.wav For that purpose at the beginning is better to use headphones connected the audio jack or external amplifier. If the sound is produced, you can try further with the board amplifier and speakers. You have to play with the potentiometer and the slide switch until sound is heard. To increase the volume if not enough you can use the "alsamixer", sliding its control up to 100%.