I can't find any indication in DS/RM, what OTG_FS_NOE pin might be good for.
OTG_FS_NOE = USB FS OTG Output Enable (active low).
This point is highlighted internally and the explanation above will be added to our documentation.
OK so I guess this is the output to control the 5V power switch/charge pump/step-up, to provide 5V VBUS for the attached device in Host mode (or if set to be OTG A-device).Correct?
So how exactly does it work? What exactly controls its state?
IMO, answers to all these questions ought to be added to RM, and Figs.494..496 updated acordingly.
Is this feature available also on other STM32, e.g. the STM32F446, which has a newer version of the OTG core?
I looked also into Cube whether I can find usage cases: in the 'L476 EVAL, the VBUS switch is controlled by a different pin (i.e. has truly be GPIO); 'L496 Disco has this switch controlled by the slave mcu; and for the 'L476 DISCO, where it's controlled by PC9 which is also said to be OTG_FS_NOE, there's no host nor OTG example in Cube...
-> In fact, it's the USB FS OTG D+/D- data line Output Enable. So this is nothing to do with enabling VBUS (which is rather treated as an input on the STM32 MCU: section “Host port power" in the reference manuals explains that we do not handle the generation of VBUS).
-> This feature is available on STM32L4 devices.
Thanks. I still don't quite understand the usage:
-> In fact, it's the USB FS OTG D+/D- data line Output Enable.
So, if OTG_FS_DP/DM are correctly set in GPIO and I don't select the respective AF for any of the OTG_FS_NOE pins, DP/DM remains always enabled; and if I select the respective AF for one of the OTG_FS_NOE, then DP/DM are enabled only when that pin is low, correct? And if it is high, DP/DM goes Hi-Z, including all the OTG_FS-related pullups/pulldowns, correct?
Looking forward to the new DS+RM appearing soon, and explaining this in detail ;-)
Thanks for the details, Khouloud.
You're always welcomed!
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