diff --git a/boards/saml21-xpro/Makefile.features b/boards/saml21-xpro/Makefile.features
index c77b406bd9..8b69fd7519 100644
--- a/boards/saml21-xpro/Makefile.features
+++ b/boards/saml21-xpro/Makefile.features
@@ -1,6 +1,7 @@
 FEATURES_PROVIDED += periph_gpio
 FEATURES_PROVIDED += periph_spi
 FEATURES_PROVIDED += cpp
+FEATURES_PROVIDED += periph_rtt
 FEATURES_PROVIDED += periph_timer
 FEATURES_PROVIDED += periph_uart
 FEATURES_MCU_GROUP = cortex_m0
diff --git a/boards/saml21-xpro/include/periph_conf.h b/boards/saml21-xpro/include/periph_conf.h
index 25aac2cdb5..37a902d578 100644
--- a/boards/saml21-xpro/include/periph_conf.h
+++ b/boards/saml21-xpro/include/periph_conf.h
@@ -94,6 +94,15 @@ extern "C" {
 #define RTC_NUMOF           (0)
 /** @} */
 
+/**
+ * @name RTT configuration
+ * @{
+ */
+#define RTT_FREQUENCY       (32768U)
+#define RTT_MAX_VALUE        (0xffffffffU)
+#define RTT_NUMOF           (1)
+/** @} */
+
 /**
  * @name GPIO configuration
  * @{
diff --git a/cpu/saml21/periph/rtt.c b/cpu/saml21/periph/rtt.c
new file mode 100644
index 0000000000..f6b66d2c02
--- /dev/null
+++ b/cpu/saml21/periph/rtt.c
@@ -0,0 +1,150 @@
+/*
+ * Copyright (C) 2015 Kaspar Schleiser <kaspar@schleiser.de>
+ *               2015 FreshTemp, LLC.
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     driver_periph
+ * @{
+ *
+ * @file        rtt.c
+ * @brief       Low-level RTT driver implementation
+ *
+ * @author      Kaspar Schleiser <kaspar@schleiser.de>
+ *
+ * @}
+ */
+
+#include <stdint.h>
+#include "periph/rtt.h"
+#include "board.h"
+#include "thread.h"
+
+#define ENABLE_DEBUG 0
+#include "debug.h"
+
+static rtt_cb_t _overflow_cb;
+static void* _overflow_arg;
+
+static rtt_cb_t _cmp0_cb;
+static void* _cmp0_arg;
+
+void rtt_init(void)
+{
+    DEBUG("%s:%d\n", __func__, __LINE__);
+    rtt_poweron();
+
+    /* reset */
+    RTC->MODE0.CTRLA.bit.SWRST = 1;
+    while(RTC->MODE0.CTRLA.bit.SWRST);
+
+    /* set 32bit counting mode */
+    RTC->MODE0.CTRLA.bit.MODE = 0;
+
+    /* set clock source */
+    OSC32KCTRL->RTCCTRL.reg = OSC32KCTRL_RTCCTRL_RTCSEL_ULP32K;
+
+    /* enable */
+    RTC->MODE0.CTRLA.bit.ENABLE = 1;
+    while(RTC->MODE0.SYNCBUSY.bit.ENABLE);
+
+    /* initially clear flag */
+    RTC->MODE0.INTFLAG.bit.CMP0 = 1;
+
+    /* enable RTT IRQ */
+    NVIC_EnableIRQ(RTC_IRQn);
+
+    DEBUG("%s:%d %u\n", __func__, __LINE__, (unsigned)rtt_get_counter());
+}
+
+void rtt_set_overflow_cb(rtt_cb_t cb, void *arg)
+{
+    DEBUG("%s:%d\n", __func__, __LINE__);
+    /* clear overflow cb to avoid race while assigning */
+    rtt_clear_overflow_cb();
+
+    /* set callback variables */
+    _overflow_cb = cb;
+    _overflow_arg = arg;
+
+    /* enable overflow interrupt */
+    RTC->MODE0.INTENSET.bit.OVF = 1;
+}
+void rtt_clear_overflow_cb(void)
+{
+    DEBUG("%s:%d\n", __func__, __LINE__);
+    /* disable overflow interrupt */
+    RTC->MODE0.INTENCLR.bit.OVF = 1;
+}
+
+uint32_t rtt_get_counter(void)
+{
+    DEBUG("%s:%d\n", __func__, __LINE__);
+    while (RTC->MODE0.SYNCBUSY.bit.COUNT);
+    return RTC->MODE0.COUNT.reg;
+}
+
+void rtt_set_alarm(uint32_t alarm, rtt_cb_t cb, void *arg)
+{
+    DEBUG("%s:%d alarm=%u\n", __func__, __LINE__, (unsigned)alarm);
+
+    /* disable interrupt to avoid race */
+    rtt_clear_alarm();
+
+    /* set COM register */
+    while (RTC->MODE0.SYNCBUSY.bit.COMP0);
+    RTC->MODE0.COMP[0].reg = alarm;
+
+    /* setup callback */
+    _cmp0_cb = cb;
+    _cmp0_arg = arg;
+
+    /* enable compare interrupt */
+    RTC->MODE0.INTENSET.bit.CMP0 = 1;
+}
+
+void rtt_clear_alarm(void)
+{
+    DEBUG("%s:%d\n", __func__, __LINE__);
+    /* clear compare interrupt */
+    RTC->MODE0.INTENCLR.bit.CMP0 = 1;
+}
+
+void rtt_poweron(void)
+{
+    DEBUG("%s:%d\n", __func__, __LINE__);
+    MCLK->APBAMASK.reg |= MCLK_APBAMASK_RTC;
+}
+
+void rtt_poweroff(void)
+{
+    DEBUG("%s:%d\n", __func__, __LINE__);
+    MCLK->APBAMASK.reg &= ~MCLK_APBAMASK_RTC;
+}
+
+void isr_rtc(void)
+{
+    if (RTC->MODE0.INTFLAG.bit.OVF) {
+        RTC->MODE0.INTFLAG.bit.OVF = 1;
+        if (_overflow_cb) {
+            _overflow_cb(_overflow_arg);
+        }
+    }
+    if (RTC->MODE0.INTFLAG.bit.CMP0) {
+        /* clear flag */
+        RTC->MODE0.INTFLAG.bit.CMP0 = 1;
+        /* disable interrupt */
+        RTC->MODE0.INTENCLR.bit.CMP0 = 1;
+        if (_cmp0_cb) {
+            _cmp0_cb(_cmp0_arg);
+        }
+    }
+
+    if (sched_context_switch_request) {
+        thread_yield();
+    }
+}