Manually enter and exit listening mode with the D0 pin

wifi-listen-true.cpp

// Configure a wifi network with a bogus name or password into the Photon
// Ground D0 to call WiFi.listen(true) while the connection attempt is ongoing
// Open, then Ground D0 again to call WiFi.listen(false)
///
#include "application.h"

SYSTEM_THREAD(ENABLED);
SYSTEM_MODE(AUTOMATIC);

void reconnectAfterListen() {
  Particle.connect();
}

void setup() {
  System.on(wifi_listen_end, reconnectAfterListen);
  pinMode(D0, INPUT_PULLUP);
}

void loop() {
  if(digitalRead(D0) == LOW) {
    if (!WiFi.listening()) {
        // Delay of ~20 seconds to enter listen mode if these 2 disconnect calls are missing
        Particle.disconnect();
        WiFi.disconnect();
        // -------------------------
        WiFi.listen(true);
    }
    else {
        WiFi.listen(false);
    }
    delay(50);
    while (digitalRead(D0) == LOW) Particle.process();
    delay(50);
  }
}