v01d commented on pull request #1252:
URL: https://github.com/apache/incubator-nuttx/pull/1252#issuecomment-644948366


   I usually use nsh config for testing. Anyway, clock selection requires 
editing the board header file. You should change the option at the top so that 
MSI is used. Then, inside the MSI section of that header, you can select MSI 
frequency by setting:
   
   #define STM32L4_BOARD_MSIRANGE    RCC_CR_MSIRANGE_48M
   
   and further below you should change:
   
   #define STM32L4_SYSCLK_FREQUENCY  48000000ul
   
   I did my tests using MSI as the main clock so you should disable the PLL 
with:
   
   #define STM32L4_BOARD_NOPLL
   
   Then choose sysclk by changing this line to:
   
   #define STM32L4_CLK48_SEL         RCC_CCIPR_CLK48SEL_MSI
   
   BTW, to my understanding all those "2*" on CLKIN definitions are not 
correct. I don't understand where that comes from, since the prescaler for 
peripheral clocks is clearly not divided by 2 as the comments a few lines above 
state. Anyway, it should not affect you.
   
   I think clock configuration should really be possible via menuconfig, I 
might work on that sometime.


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