cpu/sam3x8e: added random number generator driver

cpu/sam3x8e/periph/random.c

@@ -0,0 +1,75 @@
+/*
+ * Copyright (C) 2014 Freie Universität Berlin
+ *
+ * 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
+ * @brief       Low-level random number generator driver implementation
+ *
+ * @author      Hauke Petersen <hauke.petersen@fu-berlin.de>
+ *
+ * @}
+ */
+
+#include "cpu.h"
+#include "periph_conf.h"
+#include "periph/random.h"
+
+/* only compile this driver if enabled in the board's periph_conf.h */
+#if RANDOM_NUMOF
+
+/**
+ * @name KEY needs to be written to the config register when en|disabling
+ *       random number generation
+ */
+#define KEY             (0x524e4700)
+
+void random_init(void)
+{
+    random_poweron();
+}
+
+int random_read(char *buf, unsigned int num)
+{
+    uint32_t tmp;
+    int count = 0;
+
+    while (count < num) {
+        /* wait until new value is generated -> takes up to 84 cycles */
+        while (!(TRNG->TRNG_ISR & TRNG_ISR_DATRDY));
+        /* read 4 byte of random data */
+        tmp = TRNG->TRNG_ODATA;
+        /* extract copy bytes to result */
+        for (int i = 0; i < 4 && count < num; i++) {
+            buf[count++] = (char)tmp;
+            tmp = tmp >> 8;
+        }
+    }
+
+    return count;
+}
+
+void random_poweron(void)
+{
+    /* enable clock signal for TRNG module */
+    PMC->PMC_PCER1 |= PMC_PCER1_PID41;
+    /* enable the generation of random numbers */
+    TRNG->TRNG_CR |= (KEY | TRNG_CR_ENABLE);
+}
+
+void random_poweroff(void)
+{
+    /* disable the generation of random numbers */
+    TRNG->TRNG_CR &= ~(KEY | TRNG_CR_ENABLE);
+    /* disable clock signal for TRNG module */
+    PMC->PMC_PCER1 &= ~(PMC_PCER1_PID41);
+}
+
+#endif /* RANDOM_NUMOF */