diff --git a/hw/bsp/board_api.h b/hw/bsp/board_api.h
index a7dcabfcc..404509a28 100644
--- a/hw/bsp/board_api.h
+++ b/hw/bsp/board_api.h
@@ -97,6 +97,9 @@ static inline uint32_t board_millis(void) {
   return (((uint64_t)rt_tick_get()) * 1000 / RT_TICK_PER_SECOND);
 }
 
+#elif CFG_TUSB_OS == OPT_OS_CUSTOM
+// Implement your own board_millis() in any of .c file
+
 #else
   #error "board_millis() is not implemented for this OS"
 #endif
diff --git a/hw/bsp/stm32u5/family.c b/hw/bsp/stm32u5/family.c
index d2287e9fc..d7258a717 100644
--- a/hw/bsp/stm32u5/family.c
+++ b/hw/bsp/stm32u5/family.c
@@ -210,6 +210,19 @@ uint32_t board_button_read(void) {
   return BUTTON_STATE_ACTIVE == HAL_GPIO_ReadPin(BUTTON_PORT, BUTTON_PIN);
 }
 
+size_t board_get_unique_id(uint8_t id[], size_t max_len) {
+  (void) max_len;
+  volatile uint32_t *stm32_uuid = (volatile uint32_t *) UID_BASE;
+  uint32_t *id32 = (uint32_t *) (uintptr_t) id;
+  uint8_t const len = 12;
+
+  id32[0] = stm32_uuid[0];
+  id32[1] = stm32_uuid[1];
+  id32[2] = stm32_uuid[2];
+
+  return len;
+}
+
 int board_uart_read(uint8_t *buf, int len) {
   (void) buf;
   (void) len;