The top and bottom pin sets are the same for the headphone and amplifier out version of the sound board, we just use the headphone version for the photos below

Please note you can only connect a powered amp to the headphone jack output or L / R pins. You cannot connect the amplifier version output to another amplifier. The built in amp means they are for direct-to-speaker connection only.

The Sound Board has a lot of pins, but we can group them into chunks, lets go through each kind of group in order to understand all the stuff you can do.

Power Pins

There are a couple power pins in the top. This is what you'll use to power the Sound Board in your project.

  • Vin - This is the primary 'battery' power input pin. Power with 3-5.5 VDC
  • GND - there's a couple ground pins but we suggest this one for power input. The others can be used for signal grounds
  • BUS - this is the 5V that comes from the USB connector. We break this out in case you want to use it to say charge a LiPoly battery (See the Powering It page!)
  • PB - this is the 'Power Button' pin, which we use for testing. Just leave it disconnected for use.

In general, you'll only want to power through the Vin and GND pins. The Vin input pin is polarity protected and can use 3V-5.5V DC input. If you want to use a larger voltage, you'll need another regulator that can bring the voltage down to 3-5V DC


If you want to control the Sound Board over UART Serial, you can do so by using the TX, RX and UG pins.

  • TX - this is the serial OUT from the board. 3.3V logic
  • RX - this is the serial INTO the board. We add some level shifting so you can use 3-5V logic.
  • UG - the UART/GPIO selector pin. Pulled high for default GPIO trigger mode. Tie to ground and reset the board for UART mode.

Volume Trigger pins

These are two extra inputs that can be used to adjust the volume in GPIO trigger mode only. Connect buttons that go from each pin to ground, when the button is pressed, the volume will decrease or increase

The volume is not stored during power cycling or resets, so it will have to be re-applied after restarts.

Audio Outputs

If you don't want to use the headphone jack, connect your amplifier to the Right, Left and Ground pins. These are line level outputs for headphones of about 30 ohms, not for big speakers! There are output DC blocking capacitors so you can safely connect directly to any kind of amplifier

Trigger Pins

Finally, we're at the trigger pins! These are the 11 inputs that can be used to trigger audio playing. We'll go over how to set the file for each pin in a later page.

Each pin has a pullup resistor, use a button/switch to connect to ground when pressed in order to 'trigger' it. The board has debouncing logic built in.

Note: Trigger Pins are meant to be connected to switches   to ground and not voltage levels.

Other Pins

We have a few other pins you may be curious about

  • Rst - this is the reset pin, you probably don't need to use this pin but when tied to ground it resets the board.
  • Act - this is the Activity pin, which goes low when an audio file is played
  • CS - this is the chip select line for the onboard flash chip, do not connect anything to it! We use it for programming the chip during manufacture!

This guide was first published on Sep 23, 2014. It was last updated on Sep 23, 2014.

This page (Pinouts) was last updated on Oct 25, 2023.

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