l431: switch to HSI16 oscillator for PLL

the HSI16 is a bit more stable for CAN than the MSI

Mcu/l431/Inc/blutil.h

@@ -102,20 +102,17 @@ static inline void bl_clock_config(void)
     LL_PWR_SetRegulVoltageScaling(LL_PWR_REGU_VOLTAGE_SCALE1);
 
     while (LL_PWR_IsActiveFlag_VOS() != 0) ;
-    LL_RCC_MSI_Enable();
+    LL_RCC_HSI_Enable();
     LL_RCC_LSI_Enable();
 
     /* Wait till MSI and LSI are ready */
     while (LL_RCC_LSI_IsReady() != 1) ;
-    while (LL_RCC_MSI_IsReady() != 1) ;
+    while (LL_RCC_HSI_IsReady() != 1) ;
 
     LL_RCC_SetRTCClockSource(LL_RCC_RTC_CLKSOURCE_LSI);
     LL_RCC_EnableRTC();
 
-    LL_RCC_MSI_EnableRangeSelection();
-    LL_RCC_MSI_SetRange(LL_RCC_MSIRANGE_6);
-    LL_RCC_MSI_SetCalibTrimming(0);
-    LL_RCC_PLL_ConfigDomain_SYS(LL_RCC_PLLSOURCE_MSI, LL_RCC_PLLM_DIV_1, 40, LL_RCC_PLLR_DIV_2);
+    LL_RCC_PLL_ConfigDomain_SYS(LL_RCC_PLLSOURCE_HSI, LL_RCC_PLLM_DIV_2, 20, LL_RCC_PLLR_DIV_2);
     LL_RCC_PLL_EnableDomain_SYS();
     LL_RCC_PLL_Enable();
 
@@ -191,14 +188,11 @@ void SystemInit(void)
 
   /* Reset the RCC clock configuration to the default reset state ------------*/
   /* Set MSION bit */
-  RCC->CR |= RCC_CR_MSION;
+  RCC->CR |= RCC_CR_HSION;
 
   /* Reset CFGR register */
   RCC->CFGR = 0x00000000U;
 
-  /* Reset HSEON, CSSON , HSION, and PLLON bits */
-  RCC->CR &= 0xEAF6FFFFU;
-
   /* Reset PLLCFGR register */
   RCC->PLLCFGR = 0x00001000U;