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SSing.10
SSing.10
Associate III
May 3, 2021
Solved

Is external crystal is needed for USB communication ?

  • May 3, 2021
  • 4 replies
  • 2160 views

Hi All,

I am working on the STM32F0 series for USB based application as Mass Storage Class and completed my initial testing on the NUCLEO-F767ZI board & POC's.

Further I have done & completed my custom hardware development, but I have didn't connect external crystal(DNP) on custom board.

Did I need to confirm that, external crystal is required in custom board developed to run the USB - Mass Storage Device ?

Looking forward for responses.

Thanks & Regards

Sachin

This topic has been closed for replies.
Best answer by TDK
The STM32F730V8T6 requires an external crystal to satisfy USB timing requirements per the datasheet.

4 replies

Tesla DeLorean
Tesla DeLorean
Guru
May 3, 2021

It is recommended to keep USB clock within specification. Without it you risk issues of connectivity related to temperature, or host system implementation. ie difference in clock offset between host and device exceed tolerances.

See if it is a check-box item for USB Certification

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TDK
TDK
May 3, 2021

Some STM32F0 chips support crystal-less USB. Otherwise you need a crystal to adhere to timing requirements.

https://www.st.com/resource/en/application_note/dm00296349-usb-hardware-and-pcb-guidelines-using-stm32-mcus-stmicroelectronics.pdf

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    SSing.10
    SSing.10Author
    Associate III
    May 16, 2021

    Ok I can see some STM32 MCU are having internal USB oscillator.

    Please confirm and correct me if I am wrong in getting proper configurations & settings, I am currently using STM32F730V8T6 so does it require external oscillator for my usb related operations.

    Please confirm me for the same.

    TDK
    TDKBest answer
    May 16, 2021
    The STM32F730V8T6 requires an external crystal to satisfy USB timing requirements per the datasheet.
    "If you feel a post has answered your question, please click ""Accept as Solution""."
    SSing.10
    SSing.10Author
    Associate III
    June 9, 2021

    Hi @TDK​ ,

    Thanks for confirming the crystal requirement for STM32F730V8T6, I have assembled and it works.

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