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waclawek.jan
waclawek.jan
Super User
October 6, 2017
Solved

[OTG on 'L476] What is OTG_FS_NOE?

  • October 6, 2017
  • 8 replies
  • 2316 views
Posted on October 06, 2017 at 10:56

0690X00000608V1QAI.png

I can't find any indication in DS/RM, what OTG_FS_NOE pin might be good for.

Please, explain.

Jan Waclawek

    This topic has been closed for replies.
    Best answer by Khouloud GARSI
    Posted on November 09, 2017 at 15:59

    Hi Jan,

    • The NOE pin is only an output showing the current state of enable of the DM and DP lines. Programming AF (concerning NOE) will not in any way change the behavior of DM and DP pins.
    • After verifying, this feature is also available on STM32F0 and STM32L0 devices.
    • I have already reported this point internally and an explanation will be provided on our documentation.

    Khouloud.

    8 replies

    Khouloud GARSI
    Khouloud GARSI
    ST Employee
    October 27, 2017
    Posted on October 27, 2017 at 17:51

    Hello Jan,

    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.

    Khouloud.

    waclawek.jan
    waclawek.janAuthor
    Super User
    October 27, 2017
    Posted on October 27, 2017 at 19:06

    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    Is this feature available also on other STM32, e.g. the STM32F446, which has a newer version of the OTG core?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...

    JW

    Khouloud GARSI
    Khouloud GARSI
    ST Employee
    November 7, 2017
    Posted on November 07, 2017 at 18:12

    Hi Jan,

    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?

    -> 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).

    Is this feature available also on other STM32, e.g. the STM32F446, which has a newer version of the OTG core?

    -> This feature is available on STM32L4 devices.

    Khouloud.

    Georgi Marinov
    Georgi Marinov
    Associate
    January 24, 2019

    The output enable control signal of the analog transceiver (active low) is provided externally

    on USB_NOE. It can be used to drive some activity LED or to provide information about

    the actual communication direction to some other circuitry.

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