Power Pins

• VIN - This is the power pin - provide between 2.3 to 5V DC
• GND - This is common ground for power and logic.

I/O Pins

• SIG - The signal input pin. Provide a square wave from 20Hz to 300KHz to output to the attached piezo. The signal level does not have to match the power voltage level
• VO+ - The positive output for a piezo. 
• VO- - The negative output for a piezo. 

STEMMA Connector

The STEMMA connector is located on the left side of the front of the board, to the left of the Gain DIP switch. You can use a STEMMA JST PH 2mm 3-pin cable to connect the driver to your microcontroller board, for example this cable to connect using a breadboard.

The STEMMA connector has the following pins:

• SIGNAL (white wire) - Signal input pin
• VIN (red wire) - Power pin, 3-5VDC
• GND (black wire) - Ground pin.

Terminal Block

The terminal block is located on the right side of the front of the board, above the PAM8904 label on the board silk.

The block has the following terminals:

• VO+ - This terminal is towards the top of the board, and is located next to the x1 label on the board silk. It is the same as the VO+ pin. Connect the positive wire on your piezo to this terminal.
• VO- - This terminal is towards the bottom of the board and is located next to the PAM8904 label on the board silk. It is the same as the VO- pin. Connect the negative wire on your piezo to this terminal.

Gain Selector Switch

• Gain - The dual DIP switch at the top of the board lets you adjust the gain output from the PAM8904. You can set it to off (zero gain), x1 gain by flipping the x1 switch to ON, x2 gain by flipping the x2 switch to ON and x3 gain by flipping both the x1 and x2 switches to ON. The output is differential so 2x gain will give you 4xVin peak-to-peak across the piezo lines.

Please note: If you are powering the driver from 5VDC, don't set the gain to x3 because the 15V output is higher than the driver is specified for. So if you are using 3.3V power, x3 gain is OK and will give you about 10V out but if you're powering with 5V use 2x gain max to keep the max voltage at 10V.

Power LED and Jumper

• Power LED - On the front of the board, below the JST-PH connector, is the power LED, labeled ON. It is a green LED.
• Power LED jumper - In the lower right corner on the back of the board is a jumper for the power LED. It is labeled LED on the board silk. To disable the power LED, cut the trace on this jumper. To enable it again, solder the pads back together.

Signal LED and Jumper

• Signal LED - On the front of the board, above the JST-PH connector, is the signal LED, labeled Sig. It is a red LED. It will light-up every time a signal is received on the signal pin.
• Signal LED jumper - In the upper right corner on the back of the board is a jumper for the signal LED. It is labeled SIG on the board silk. To disable the signal LED, cut the trace on this jumper. To enable it again, solder the pads back together.