Generate device name

esp32_device/main/random.c

@@ -0,0 +1,31 @@
+#include "random.h"
+#include "esp_random.h"
+
+void rand_str(size_t len, char *dest)
+{
+    for (size_t i = 0; i < len; i++)
+    {
+        uint32_t v = esp_random() % (26 * 2 + 10);
+
+        // Upper case letter
+        if (v < 26)
+        {
+            dest[i] = 65 + v;
+            continue;
+        }
+        v -= 26;
+
+        // Lower case letter
+        if (v < 26)
+        {
+            dest[i] = 97 + v;
+            continue;
+        }
+        v -= 26;
+
+        // Digit
+        dest[i] = 48 + (v % 10);
+    }
+
+    dest[len] = '\0';
+}