Can I use a 6 pin Bluetooth module in a 4 pin socket? I have a Funduino joystick shield and it features a 4 pin bluetooth socket in the top right hand corner (just above the D, T, - and + legends).



For some reason, on eBay, 6 pin bluetooth modules are cheaper and more common than 4 pin bluetooth modules. 



The joystick shield's 4 pin socket is labelled R T - +. Obviously these correspond with RXD, TXD, GND and VCC on the bluetooth module. 

I was wondering:


What is the difference between the 4 pin and 6 pin modules?
Can I use a 6 pin module in the four pin socket on the joystick shield?
What is the function of additional STATE and EN pins on the bluetooth module?
Are these two additional pins necessary as other modules do not have them?
After some more concerted searching I have found the answer on Success Using the JY-MCU (linvor) Bluetooth Module:


  The module has 6 pins labeled on the back, but most modules only have
  4 of those populated with pogo pins.  KEY &amp; STATE seem to be not
  required, as KEY is used for flashing the device and STATE simply
  indicates if the device is awake or not.  So that leaves only GND,
  VCC, TXD, RXD.  Not shown is Pin 11 which is the RESET pin, resetting
  the module when pulled LOW.


So, the answer is apparently yes, and you can buy a cheaper 6 pin module and remove (snip/desolder) the two additional pins.  The EN pin is also apparently labelled as KEY on some modules.