Merge pull request #6821 from haukepetersen/add_stm32l4_hwrng

boards/cpu: added hwrng for nucleo-l476 / stm32l4

boards/nucleo-l476/Makefile.features

@@ -1,6 +1,7 @@
 # Put defined MCU peripherals here (in alphabetical order)
 FEATURES_PROVIDED += periph_cpuid
 FEATURES_PROVIDED += periph_gpio
+FEATURES_PROVIDED += periph_hwrng
 FEATURES_PROVIDED += periph_pwm
 FEATURES_PROVIDED += periph_spi
 FEATURES_PROVIDED += periph_timer

cpu/stm32l4/cpu.c

@@ -143,6 +143,9 @@ static void cpu_clock_init(void)
     while (!(RCC->CSR & RCC_CSR_LSIRDY)) {}
 #endif
 
+    /* select the MSI clock for the 48MHz clock tree (USB, RNG) */
+    RCC->CCIPR = (RCC_CCIPR_CLK48SEL_0 | RCC_CCIPR_CLK48SEL_1);
+
     /* if configured: enable the HSE clock */
 #if CLOCK_HSE
     RCC->CR |= RCC_CR_HSEON;

tests/periph_hwrng/main.c

@@ -31,7 +31,7 @@ int main(void)
     uint8_t buf[LIMIT];
 
     puts("\nHWRNG peripheral driver test\n");
-    printf("This test will print from 1 to %i random bytes about every"
+    printf("This test will print from 1 to %i random bytes about every "
            "second\n\n", LIMIT);
 
     puts("Initializing the HWRNG driver.\n");