I2S Interface

The expansion board provides one I2S port at the breakout connector to enable the connection of audio-based devices.

I2S Mapping to Breakout Connectors

Pin #

Signal Name

Direction Looking
into Breakout
Connector

Signal Description

J12.12

I2S_1_RXD_LS

Input

Audio data input to the expansion board, from an I2S compliant audio input device on the breakout board.

J12.14

I2S_1_TXD_LS

Output

Audio data output to an I2S compliant audio output device on the breakout board.

J12.16

I2S_1_FS_LS

Output

Audio left/right frame select signal to an I2S compliant audio device on the breakout board.

J12.18

I2S_1_CLK_LS

Input/Output

Audio bit clock output/input to an I2S compliant audio device on the breakout board.

Note: Direction can change for slave or master mode.

I2S Level Transitions

The breakout board must include pullup resistors to the logic levels required by the audio device on the breakout board, but not to exceed 3.3 V. The pullups are from the I2S signals to a 3.3 V source. We recommend using J13 pin 6 or 8 as the 3.3 V source for the pullup resistors.

Level translation is performed by a Texas Instruments* LSF0108RKSR open drain translator.

The expansion board uses a 200 kΩ pullup resistor from the +V3P3V supply to enable EU17 when the expansion board is active.

See I2S Interface Specifications for I2S technical specifications.

Audio Signal Termination and Conditioning

For information about signal termination and conditioning, definitions of the values in the following table, and how the values were measured, refer to Termination and Conditioning. For an example of how to wire a pullup resistor for a 3.3 V pullup voltage, refer to GPIO Signal Termination and Conditioning.

SPI signal level translation termination recommendations

Signal Name

Pullup Voltage

Rmin (Ω)

CLOAD (pF)

Trise (ns)

Tfall (ns)

I2S_1_CLK_LS

I2S_1_FS_LS

I2S_1_RXD_LS

I2S_1_TXD_LS

3.3 1100 47 56 17

 

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