['F446 documentation] SAI/SPDIF-Tx bit clock formula missing

The formula I mentioned above I've seen in 'F7 documentation is wrong anyway:

as fS is not fSCK_x/64; and certainly not fSAI_CK_x / 64.

And this is wrong, too:

as it's not just the input frequency to SAI block, i.e. fSAI_CK_x , which is alone responsible for the resulting sampling frequency.

The fact is that (denoting the SPDIF symbol rate fSYMB) fS = fSYMB / 64; but fSYMB=fSCK_x / 2.

And, fSCK_x follows the same rules as in FREE mode, i.e. fSCK_x = fSAI_CK_x if NODIV=1; fSCK_x = fSAI_CK_x / (256 / (FRL+1)) if NODIV=

1

[EDIT]was a typo, sorry[/EDIT]

In other words, the final fS-to-fSAI_SCK_x ratio is half of what would be for the FREE mode with the same NODIV and MCKDIV settings.

Of course, Cube gets it wrong, too; as it does not account for this factor of half. The only example I could find for SAI in SPDIF-Tx mode (namely in [STM32Cube_FW_F7_V1.7.0]\Projects\STM32F769I-Discovery\Examples\SPDIFRX\SPDIFRX_Loopback\) has no visible/audible output, and uses as receiver the SPDIFRX module, which is adaptive enough to ignore the fact that the output sample rate is half of what was intended.

JW