Looking into accuracy of internal oscillator, and wondering if it is sufficient to drive USB as virtual COM port over large variance in temperatures.

MCrew.1 · ‎2020-09-22

I am using the STM32L476 MCU on a board that will be used on a boat with varying temperature conditions, and using the USB as a virtual COM port to send and receive data for diagnostics of the board. When configuring the clock using the MSI to drive 48MHz, will this internal oscillator be accurate to operate over a large variance of temperatures? Or will I need to use an external clock?

TDK · ‎2020-09-22

The L4 has a clock recovery system. If you use that, you can use USB without a crystal. The MSI by itself is not accurate enough.

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waclawek.jan · ‎2020-09-22

> The L4 has a clock recovery system

Not the 'L476, though.

JW

MCrew.1 · ‎2020-09-22

Can you explain how to use the clock recovery system?

TDK · ‎2020-09-22

I could, but it seems your chip doesn't have it so it wouldn't be much use.

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MCrew.1 · ‎2020-09-24

Does the L496 have a clock recovery system? If so, can you explain how it would be used? Considering switching chips from the L476 to the L496.

MCrew.1 · ‎2020-09-24

Or would the HSI48 be accurate for the application as specified above?