Peter Drescher / ST_L152_32MHZ

Lib to change the clock speed of the ST Nucleo L152RE board to 32 MHz.

The ST Nucleo L152 board is running on 16 MHz out of the box. To speed up the cpu to the maximum 32MHz speed we have to change the clock setting. Simply add the lib and : 

         #include "ST_L152_32MHZ.h"
        L152_init32 myinit(0);   // use the internal oscillator

in front of your program. This should be the first line in main to ensure the frequency is changed before other objects are initialised.

This frequency is generated out of the internal RC oscillator. The frequency is not so stable like a crystal. The PLL is switched to 96MHz to enable the use of the USB interface.

If you need a more precise timing source, you have to add a external crystal.

/media/uploads/dreschpe/oszillator.jpg

You need : X3 8MHz crystal , C33 and C34 18pF 0603 , R35 and R37 have to be short with a small piece of wire.

         #include "ST_L152_32MHZ.h"
        L152_init32 myinit(1);   // use external crystal oscillator

Files at this revision

API Documentation at this revision

Revision 3:1e82f1f333ad, committed 2014-04-08

Comitter:
dreschpe
Date:
Tue Apr 08 17:17:56 2014 +0000
Parent:
2:9e2ba1d93567
Commit message:
We have to reset the clock setting to change the pll

Changed in this revision

ST_L152_32MHZ.cpp Show annotated file Show diff for this revision Revisions of this file 
diff -r 9e2ba1d93567 -r 1e82f1f333ad ST_L152_32MHZ.cpp
--- a/ST_L152_32MHZ.cpp	Wed Mar 19 18:07:11 2014 +0000
+++ b/ST_L152_32MHZ.cpp	Tue Apr 08 17:17:56 2014 +0000
@@ -30,7 +30,7 @@
 {
     uint32_t PLLStartUpCounter = 0,PLLStatus = 0,error;
 
-
+    RCC_DeInit();  // we have to reset the clock settings !
 /* Enable 64-bit access */
     FLASH->ACR |= FLASH_ACR_ACC64;