Add API for random number generator

components/esp32/hw_random.c

@@ -0,0 +1,33 @@
+// Copyright 2016 Espressif Systems (Shanghai) PTE LTD
+//
+// 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 <stdint.h>
+#include <stddef.h>
+#include <string.h>
+#include "esp_attr.h"
+#include "soc/wdev_reg.h"
+#include "freertos/FreeRTOSConfig.h"
+#include "xtensa/core-macros.h"
+
+uint32_t IRAM_ATTR esp_random(void)
+{
+    static uint32_t last_ccount = 0;
+    uint32_t ccount;
+    do {
+        ccount = XTHAL_GET_CCOUNT();
+    } while (ccount - last_ccount < XT_CLOCK_FREQ / APB_CLK_FREQ * 16);
+    last_ccount = ccount;
+    return REG_READ(WDEV_RND_REG);
+}