ESP8266 Community Forum

You have to reflash it. This is only way. I had the same problem.
AP+UPDATE often bricks module, my advice is: do not use it.

That's a very long story....

Because Espressif AT was open source before..

So many developer developed AT software based on Espressif Official AT and set a different configuration ..

But they didn't change the function "AT+CIUPDATE" , so when you upgrade , you upgrade back to Espressif official AT ... which baudrate is 115200 and AT commands end with CR LF ...

Because of configuration differences ( baudrate changed , maybe ends also changed )... user may be confused ...

Always recommended you to use Espressif official AT http://bbs.espressif.com/viewtopic.php?f=5&t=154

http://ppl.ug/dwtD9Z8jrWY/ here is some more info on the current sdk.

I got same problem when I try command "AT+CIUPDATE" I get response upto 3 and then unknowen text comes appear but but then I wait for at least 30 mins then it stop automatically and I just disconnect everything I restart my Laptop and again conncect every wire of esp8266 with arduino and then I am able to use it.... so my friends dont loose your hope and wait untile it stops automatically....