I2S Amplifier

• The grey square located towards the top right of the BFF is the MAX98357 I2S amplifier chip. It supports digital audio.

Default I2S Pins

These pins are compatible with ESP32-series, nRF52840 and RP2040 microcontroller boards.

• A1 - This is used for audio data, or DAT.
• A2 - This is used for wordselect clock, or LR.
• A3 - This is used for bitclock, or BCLK.

Default SD Card Pins

The SD Card is connected to the default SPI pins on the QT Py. SDCS is connected to pin A0.

• MO - This is the SPI MOSI (Microcontroller Out / Serial In) pin. It is used to send data from the microcontroller to the SD card. It is connected to the default MOSI pin on the QT Py.
• MI - This is the SPI MISO (Microcontroller In / Serial Out) pin. It's used for sending data from the SD card to the microcontroller. It is connected to the default MISO pin on the QT Py.
• SCK - This is the SPI clock input pin. It is connected to the default SCK pin on the QT Py.
• A0 - This is the SD chip select pin (SDCS).

I2S Gain Jumper

On the back of the board, towards the top, are the I2S gain jumper pads. They are outlined in white on the board silk and are labeled Gain. The default gain for the amplifier is 9 dB.

• To set the gain to 6 dB, solder the center jumper, labeled 9, to the jumper above labeled 6. This connects the GAIN pin on the I2S amplifier to 5V.
• To set the gain to 12 dB, solder the center jumper, labeled 9, to the right jumper below labeled 12. This connects the GAIN pin on the I2S amplifier to GND.

Speaker Connector

• This two-pin PicoBlade-compatible speaker connector, located at the center of the front of the BFF, is meant for plugging in a 4-8Ω, 3W-or-less speaker.
• To connect a speaker with bare wires, you'll want to pick up this cable.
• If you need a speaker, this speaker is an excellent place to start.

micro SD Card Slot

• On the front of the board, towards the bottom, is the micro SD card slot. You can use any micro SD card that supports SPI mode with one CS pin.