Adding implementation for Sleep APIs. Not completely tested.

libraries/mbed/targets/hal/TARGET_Atmel/TARGET_SAM21/TARGET_SAMR21G18A/device.h

@@ -49,7 +49,7 @@
 #define DEVICE_ID_LENGTH        0
 #define DEVICE_MAC_OFFSET       0
 
-#define DEVICE_SLEEP            0
+#define DEVICE_SLEEP            1
 
 #define DEVICE_DEBUG_AWARENESS  0
 

libraries/mbed/targets/hal/TARGET_Atmel/TARGET_SAM21/sleep_api.c

@@ -0,0 +1,49 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2006-2013 ARM Limited
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#include "mbed_assert.h"
+#include "sleep_api.h"
+
+#include <math.h>
+
+#include "cmsis.h"
+#include "power.h"
+
+/** Send the device to sleep
+ *
+ * The processor is setup ready for sleep, and sent to sleep using __WFI(). In this mode, the
+ * system clock to the core is stopped until a reset or an interrupt occurs.
+ * @param[void] void
+ * @return      void
+ */
+void sleep(void)
+{
+	system_set_sleepmode(SYSTEM_SLEEPMODE_IDLE_2);
+	system_sleep();
+}
+
+/** Send the device to deep sleep
+ *
+ * This processor is setup ready for deep sleep, and sent to sleep using __WFI(). This mode
+ * has the same sleep features as sleep plus it powers down peripherals and clocks. All state
+ * is still maintained.
+ * @param[void] void
+ * @return      void
+ */
+void deepsleep(void)
+{
+	system_set_sleepmode(SYSTEM_SLEEPMODE_STANDBY);
+	system_sleep();
+}