Manufacturers of I2S-compatible devices notoriously label the signals in various ways.
The standard says:
3.0 THE I 2 S BUS
As shown in Figure 1, the bus has three lines:
• continuous serial clock (SCK);
• word select (WS);
• serial data (SD);
and the device generating SCK and WS is the master.
ST follows this nomenclature relatively well.
standard ST various manufacturers
SCK (Serial Clock) I2Sx_CK SCLK, BICK (Bit Clock)
WS (Word Select) I2Sx_WS LRCK (Left-Right Clock)
SD (Serial Data) I2Sx_SD SDIN/SDOUT, SDTI/SDTO, RXDAT/TXDAT, DACDAT/ADCDAT
There is an additional nonstandard but often used signal I2Sx_MCK/MCLK.
The SPI/I2S module in STM32 is simplex but the data direction is settable (Rx/Tx) that's why it's not marked at the pin, and it's marked as I2Sx_SD.
There are auxiliary stripped-down I2S-slave-only modules, I2SxExt - as they are slave-only and their WS and SCK clocks are connected internally to their respective "master" module, they have only a single pin brought out, I2SxExt_SD.
Refer to the F4 Disco boards (e.g. https://www.st.com/en/evaluation-tools/stm32f4discovery.html ) for reference, they have an I2S DAC on board. Maybe the EVAL boards have I2S device on board, too.
JW
