Switch from HSE to HSI on failure of the HSE?

[sima2]

Posted on August 15, 2011 at 13:50

Hello

I would like to switch from the HSE oscilator to the HSI oscilator if there is a failure of the HSE oscilator. How can I do that with preserved SYSCLK (64MHz)? The HSI klock is divided på 2 så the PLL would need to be changed by a factor of 2.

[Tesla DeLorean]

Posted on August 15, 2011 at 14:32

PLLXTPRE (RCC_CFGR) permits you to feed HSE/2 into the PLL.

Although losing a synchronous clock, and switching a locked PLL to a different clock (even slightly), is a whole barrel of fun.