Switching between the system clock sources

nanayakkaraan · ‎2010-11-18

Posted on November 19, 2010 at 05:42

Tesla DeLorean · ‎2011-05-17

Posted on May 17, 2011 at 14:15

I think you are one of a handful using the STM32L

The sequence will likely go

Enable HSI

Wait for HSI to start

Switch to HSI

Wait for HSI to become source

Disable other clocks (MSI, etc)

There should be examples of this, or other clock switches, in the STM32L or other STM32 series parts.

The reverse sequence will likely go

Enable MSI

Wait for MSI to start

Switch to MSI

Wait for MSI to become source

Disable other clocks (HSI, etc)

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picguy2 · ‎2011-05-17

Posted on May 17, 2011 at 14:15

Just do it. But do understand that some processors and debuggers can do bad stuff.

I’m a “just do it�? kind of guy. But that cost me $49+s/h on a non-ST demo board. I stopped the clock leaving the debugger no way to recover. Thereafter I first prove that I can read a push button on the demo board and loop waiting until it is released before going on. If I kill something real bad I can boot with the button pressed and stop things before my code messes up.

It’s only a little code and can be left in production code. Pull the pin up. Then when needed ground the pin. Program then waits before any clock changing.

nanayakkaraan · ‎2011-05-17

Posted on May 17, 2011 at 14:15

Hello clive1,

Thank you for replying. 🙂

Will give it a try later.