Modified the test_reset.ino example.

In this new version, the program gives more meaningful strings about the reset source (no more "Unknown" when more sources are triggered).
Moreover the program will not wait for some time before triggering a WDT reset, and clearly asks the user to press a button to reset using that peripheral
Finally, since this program should only run once, the majority of the program is moved to the setup function rather than the loop

optiboot/examples/test_reset/test_reset.ino

@@ -36,47 +36,48 @@ void resetFlagsInit(void)
 
 void setup() {
   Serial.begin(9600);  // Initialize serial port
-}
-
-void loop() {
+  
   Serial.println("Reset flag test");
-  while (Serial.read() < 0)
-    ;  // wait for some type-in
-
+  
   Serial.print("Have reset flag value 0x");
   Serial.print(resetFlags, HEX);
+  
   /*
    * check for the usual bits.  Note that the symnbols defined in wdt.h are
    * bit numbers, so they have to be shifted before comparison.
    */
-  switch (resetFlags) {
-    case 1<<WDRF:
-      Serial.println(" (Watchdog)\n");
-      break;
-    case 1<<BORF:
-      Serial.println(" (Brownout)\n");
-      break;
-    case 1<<EXTRF:
-      Serial.println(" (External Reset)\n");
-      break;
-    case  1<<PORF:
-    case ((1<<PORF) | (1<<BORF)):
-      // A poweron can frequently result in both PORF and BORF being set, as the
-      //  power switch bounces or the voltage rises slowly.
-      Serial.println(" (PowerOn)\n");
-      break;
-    default:
-      // Multiple bits can be set under various circumstances.  For example, the
-      //  "hold down reset while powering up" trick used to recover from certain
-      //  problems can leave both PORF and EXTRF set.
-      Serial.println(" (Unknown)\n");
-      break;
+  if (resetFlags & (1<<WDRF))
+  {
+    Serial.print(" Watchdog");
+    resetFlags &= ~(1<<WDRF);
   }
-  /*
-   * Now we'll let the Watchdog reset the chip, and see if that cause is reported
-   * correctly.  Older versions of optiboot could not easily distinguish between
-   * WDRF and EXTRF resets, since the WDT was used inside the bootloader.
-   */
-  wdt_enable(WDTO_1S);
+  if (resetFlags & (1<<BORF))
+  {
+    Serial.print(" Brownout");
+    resetFlags &= ~(1<<BORF);
+  }
+  if (resetFlags & (1<<EXTRF))
+  {
+    Serial.print(" External");
+    resetFlags &= ~(1<<EXTRF);
+  }
+  if (resetFlags & (1<<PORF))
+  {
+    Serial.print(" PowerOn");
+    resetFlags &= ~(1<<PORF);
+  }
+  if (resetFlags != 0x00)
+  {
+    // It should never enter here
+    Serial.print(" Unknown");
+  }
+  Serial.println("");
+}
+
+void loop() {
+  Serial.println("Send something to reset through watchdog peripheral");
+  while (Serial.read() < 0) ;
+  wdt_enable(WDTO_15MS);
+  while (1); // To prevent the loop to start again before WDT resets the board
 }