One quick note: In order to put the HC-05 into AT mode, you must:
1.) Disconnect power to the module
2.) If your HC-05 breakout board has a "KEY" pin, set that HIGH (3v3) - if not, press and hold the tiny pushbutton on the top of the module
3.) Reconnect power to the module (5V for most breakout boards)
4.) Drive "KEY" pin low if "KEY" pin present - if not, let go of the pushbutton <--- Only disengage the "KEY" or pushbutton if the above program says you can, otherwise keep "KEY" high/pushbutton pressed until all AT commands that need your HC-05 in that configuration are done
Also, HC-06 modules can be put into AT mode at anytime - no buttons or extra pins required.
Lastly, the "EN" pin IS NOT THE SAME as the "KEY" pin. "EN" pin will "enable" (turn on and off) the module based on the pin's voltage level.