@weasel79 Just saw your DM. I was going to give a similar answer to what @deadsy mentioned. The codec is on the SAI peripheral. SPI3 can be switched into an I2S mode. SPI3 is currently left free with the idea of using it for multiprocessor sync. See the latest schematic. SPI2 can also technically be switched into I2S mode, but there look to be a couple of pin conflicts with the existing configuration that might need to be adjusted (PC2/PC3 are currently assigned to ADC and PB10 to USART3TX). I don't have time at the moment to fully verify if there are any restrictions about what combination of these peripherals can be activated simultaneously. SPI3 (PC10, PC11, PC12, PA10) would be the quickest to get going with I2S I think without needing any external hardware. Just to be clear I'm talking specifically about Axo core and the 427 processor.
Expanding on that first datasheet:
"When the I²S feature (included in the SPI peripheral) is not available or is already used
(full-duplex or multiple audio codec system), it is possible to emulate the I²S protocol master
or slave using standard SPI and timer peripherals."
I don't believe this is the case for us because the SPI peripherals we're talking about have an explicit I2S mode. Manual emulation should not be necessary. That would be a last resort.
Edit: I meant to say 427. The 407 is really similar with respect to I2S being multiplexed on the SPI channels but it lacks a SAI. @weasel79 Did you mean 427?