diff --git a/ports/stm/common-hal/alarm/SleepMemory.c b/ports/stm/common-hal/alarm/SleepMemory.c
index 3b89efbca3..dc19222d63 100644
--- a/ports/stm/common-hal/alarm/SleepMemory.c
+++ b/ports/stm/common-hal/alarm/SleepMemory.c
@@ -29,21 +29,45 @@
 #include "py/runtime.h"
 #include "common-hal/alarm/SleepMemory.h"
 
+#include STM32_HAL_H
+
+#define STM_BKPSRAM_SIZE    0x1000
+#define STM_BKPSRAM_START   BKPSRAM_BASE
+
+STATIC bool initialized = false;
+
+STATIC void lazy_init(void) {
+    if (!initialized) {
+        __HAL_RCC_BKPSRAM_CLK_ENABLE();
+        HAL_PWREx_EnableBkUpReg();
+        HAL_PWR_EnableBkUpAccess();
+        initialized = true;
+    }
+}
+
 void alarm_sleep_memory_reset(void) {
 
 }
 
 uint32_t common_hal_alarm_sleep_memory_get_length(alarm_sleep_memory_obj_t *self) {
-    mp_raise_NotImplementedError(translate("Sleep Memory not available"));
-    return 0;
+    lazy_init();
+    return STM_BKPSRAM_SIZE;
 }
 
 bool common_hal_alarm_sleep_memory_set_bytes(alarm_sleep_memory_obj_t *self, uint32_t start_index, const uint8_t *values, uint32_t len) {
-    mp_raise_NotImplementedError(translate("Sleep Memory not available"));
-    return false;
+    if (start_index + len > STM_BKPSRAM_SIZE) {
+        return false;
+    }
+    lazy_init();
+    memcpy((uint8_t *)(STM_BKPSRAM_START + start_index), values, len);
+    return true;
 }
 
 void common_hal_alarm_sleep_memory_get_bytes(alarm_sleep_memory_obj_t *self, uint32_t start_index, uint8_t *values, uint32_t len) {
-    mp_raise_NotImplementedError(translate("Sleep Memory not available"));
+    if (start_index + len > STM_BKPSRAM_SIZE) {
+        return;
+    }
+    lazy_init();
+    memcpy(values, (uint8_t *)(STM_BKPSRAM_START + start_index), len);
     return;
 }