Reboot on button press when halted but still have power

libraries/badger2040/badger2040.cpp

@@ -2,6 +2,7 @@
 #include <math.h>
 
 #include "hardware/pwm.h"
+#include "hardware/watchdog.h"
 
 #include "badger2040.hpp"
 
@@ -79,8 +80,10 @@ namespace pimoroni {
   void Badger2040::halt() {
     gpio_put(ENABLE_3V3, 0);
 
-    // don't allow any more code to execute while power rail drops
-    while(true) {}
+    // If running on USB we will not actually power down, so emulate the behaviour
+    // of battery powered badge by listening for a button press and then resetting
+    wait_for_press();
+    watchdog_reboot(0, 0, 0);
   }
 
   uint8_t _dither_value(int32_t x, int32_t y, uint8_t p) {