diff --git a/hal/architecture/MyHw.h b/hal/architecture/MyHw.h
index fd78f47..3288ff9 100644
--- a/hal/architecture/MyHw.h
+++ b/hal/architecture/MyHw.h
@@ -51,18 +51,13 @@ uint8_t hwReadConfig(int adr);
  */
 //#define MY_HW_HAS_GETRANDOM
 
-/**
- * Sleep for a defined time, using minimum power.
- * @param ms   Time to sleep, in [ms].
- * @return Nonsense, please ignore.
- */
-
+/// @brief unique ID
 typedef uint8_t unique_id_t[16];
 
 /**
  * Sleep for a defined time, using minimum power.
  * @param ms         Time to sleep, in [ms].
- * @return -1.
+ * @return MY_WAKE_UP_BY_TIMER.
  */
 int8_t hwSleep(unsigned long ms);
 
@@ -71,7 +66,7 @@ int8_t hwSleep(unsigned long ms);
  * @param interrupt  Interrupt number, which can wake the mcu from sleep.
  * @param mode       Interrupt mode, as passed to attachInterrupt.
  * @param ms         Time to sleep, in [ms].
- * @return -1 when woken by timer, or interrupt number when woken by interrupt.
+ * @return MY_WAKE_UP_BY_TIMER when woken by timer, or interrupt number when woken by interrupt.
  */
 int8_t hwSleep(uint8_t interrupt, uint8_t mode, unsigned long ms);
 
@@ -82,14 +77,14 @@ int8_t hwSleep(uint8_t interrupt, uint8_t mode, unsigned long ms);
  * @param interrupt2  Interrupt2 number, which can wake the mcu from sleep.
  * @param mode2       Interrupt2 mode, as passed to attachInterrupt.
  * @param ms          Time to sleep, in [ms].
- * @return -1 when woken by timer, or interrupt number when woken by interrupt.
+ * @return MY_WAKE_UP_BY_TIMER when woken by timer, or interrupt number when woken by interrupt.
  */
 int8_t hwSleep(uint8_t interrupt1, uint8_t mode1, uint8_t interrupt2, uint8_t mode2,
                unsigned long ms);
 
 /**
 * Retrieve unique ID
-* @param uniqueID uniqueID
+* @param uniqueID unique ID
 * @return True if unique ID successfully retrieved
 */
 bool hwUniqueID(unique_id_t* uniqueID);
diff --git a/hal/architecture/MyHwTeensy3.cpp b/hal/architecture/MyHwTeensy3.cpp
index 391dc43..e84c65e 100644
--- a/hal/architecture/MyHwTeensy3.cpp
+++ b/hal/architecture/MyHwTeensy3.cpp
@@ -132,6 +132,24 @@ uint16_t hwFreeMem()
 	return FUNCTION_NOT_SUPPORTED;
 }
 
+void hwRandomNumberInit(void)
+{
+#if defined(__MK64FX512__) || defined(__MK66FX1M0__)
+	// use HW RNG present on Teensy3.5/3.6
+	// init RNG
+	SIM_SCGC6 |= SIM_SCGC6_RNGA; // enable RNG
+	RNG_CR &= ~RNG_CR_SLP_MASK;
+	RNG_CR |= RNG_CR_HA_MASK;  // high assurance
+	// get random number
+	RNG_CR |= RNG_CR_GO_MASK;
+	while (!(RNG_SR & RNG_SR_OREG_LVL(0xF)));
+	const uint32_t seed = RNG_OR;
+	randomSeed(seed);
+#else
+	randomSeed(analogRead(MY_SIGNING_SOFT_RANDOMSEED_PIN));
+#endif
+}
+
 void hwDebugPrint(const char *fmt, ...)
 {
 	char fmtBuffer[MY_SERIAL_OUTPUT_SIZE];
diff --git a/hal/architecture/MyHwTeensy3.h b/hal/architecture/MyHwTeensy3.h
index c8bd02f..529f603 100644
--- a/hal/architecture/MyHwTeensy3.h
+++ b/hal/architecture/MyHwTeensy3.h
@@ -38,15 +38,25 @@
 #define _BV(x) (1<<(x))
 #endif
 
+#if defined(__MK64FX512__) || defined(__MK66FX1M0__)
+#define RNG_CR_GO_MASK			0x1u
+#define RNG_CR_HA_MASK			0x2u
+#define RNG_CR_INTM_MASK		0x4u
+#define RNG_CR_CLRI_MASK		0x8u
+#define RNG_CR_SLP_MASK			0x10u
+#define RNG_SR_OREG_LVL_MASK	0xFF00u
+#define RNG_SR_OREG_LVL_SHIFT	8
+#define RNG_SR_OREG_LVL(x)		(((uint32_t)(((uint32_t)(x))<<RNG_SR_OREG_LVL_SHIFT))&RNG_SR_OREG_LVL_MASK)
+#define SIM_SCGC6_RNGA			((uint32_t)0x00000200)
+#endif
+
 // Define these as macros to save valuable space
 #define hwDigitalWrite(__pin, __value) digitalWriteFast(__pin, __value)
 #define hwDigitalRead(__pin) digitalReadFast(__pin)
 #define hwPinMode(__pin, __value) pinMode(__pin, __value)
 #define hwMillis() millis()
 
-// TODO: use hardware random number generator if Teensy 3.5 or 3.6
-#define hwRandomNumberInit() randomSeed(analogRead(MY_SIGNING_SOFT_RANDOMSEED_PIN))
-
+void hwRandomNumberInit(void);
 bool hwInit(void);
 void hwWatchdogReset(void);
 void hwReboot(void);