#include <ESP8266WiFi.h>
#include <DNSServer.h>
#include <ESP8266WebServer.h>
#include <WiFiManager.h>
#include <Ticker.h>
int ledOutput = LED_BUILTIN;//板载LED灯
Ticker ticker;//实例化定时器

void setup() {
 Serial.begin(9600);//打开串口通讯
 pinMode(ledOutput,OUTPUT);//初始化LED状态
 ticker.attach(0.1,wifiStatus);//定时执行LED的取反，直到WIFI连接
 WiFiManager wifiManager;//实例化自动配网
 wifiManager.autoConnect("AP");//启动自动配网
 Serial.println("");
 Serial.print("ESP8266 Connected to ");
 Serial.println(WiFi.SSID());
 Serial.print("IP address:\t");
 Serial.println(WiFi.localIP());

}
void wifiStatus(){
  if (WiFi.status() == WL_CONNECTED){//判断WIFI是否连接
    digitalWrite(ledOutput,HIGH);//设置为高。LED灭
     ticker.detach();
    }
  else {
    digitalWrite(ledOutput,!digitalRead(ledOutput));//取返led
    }  
  
  }

void loop() {
  // put your main code here, to run repeatedly:

}

利用ticker定时器，每100毫秒检测wifi连接情况，没连接就取反LED提示进行配网，连接成功pin脚为高。关闭led