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EFish.1
EFish.1
Visitor II
July 9, 2020
Question

Do I need an external crystal if I want to use the STM32F412 USB FS device ? or can I use the internal HSI ?

  • July 9, 2020
  • 9 replies
  • 2079 views

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9 replies

berendi
berendi
Principal
July 9, 2020

Yes, the internal oscillator can not provide the accuracy required by USB.

frank.zhao
frank.zhao
Associate II
July 9, 2020

STM32 chips with crystal-less USB are

STM32F072

STM32F078

STM32F04x

STM32F105/107

STM32H743/753

STM32H750

STM32L0x2

STM32L0x3

STM32L4x2

STM32L4x3

STM32L4x5

STM32L4x6

STM32L4Rx

STM32L4Sx

Terry Greeniaus
Terry Greeniaus
Senior
July 9, 2020

The G4 series also has crystal-less USB using the CRS.

waclawek.jan
waclawek.jan
Super User
July 9, 2020

I wonder how would 'F105/107 work crystal-less. Can you please post source?

JW

frank.zhao
frank.zhao
Associate II
July 9, 2020

@Community member​ I'm reading AN4879 "USB implementation on STM32 products", section 2.1, table 4 "USB implementation on STM32 mainstream products". F105/107 does indeed have a X under crystal-less. But reading the datasheet I can't see that feature.

waclawek.jan
waclawek.jan
Super User
July 9, 2020

@Imen DAHMEN​  Hi, this appears to be an error, can you please have a look at it?

Thanks,

Jan

Imen.D
ST Technical Moderator
July 10, 2020

Ok, I will check and raise it internally for fix.

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waclawek.jan
waclawek.jan
Super User
July 10, 2020

Thanks, Imen.

JW

S.Ma
S.Ma
Principal
July 9, 2020

To complement: Most STM32L4 have MSI which generates 48MHz from the 32.768kHz LSE and is suitable for USB Device function without LSE.

In Host mode, HSE crystal becomes required.

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