user31322: I have an Arduino Mega 2560 and a BLE Shield v 2.1 from RedBearLab. When I try to connect it through Bluetooth from my laptop to 'BLE Shield', it says 'Connected!'. When I try from a Windows phone, it also says 'Connected'. 
But when I try to connect from an Android device, it gives me an error: 'pairing rejected by BLE shield' or 'couldn't pair with BLE Shield because of an incorrect PIN or passkey'.
What seems to be the problem?

user10394: I would guess that the problem is an incorrect PIN or passkey. 
I've read from manuals for some gadgets that some devices/phones automatically try the PIN 0000 and some don't.  I have never seen my Windows phone ask for a PIN when the device hasn't got one set, so I'm guessing that Windows automatically tries 0000 and Android doesn't.  Is there a  setting on Android that will let you enter the pin (which is probably 0000) ?

31322: <p>I have an Arduino Mega 2560 and a BLE Shield v 2.1 from RedBearLab. When I try to connect it through Bluetooth from my laptop to 'BLE Shield', it says 'Connected!'. When I try from a Windows phone, it also says 'Connected'. </p>

<p>But when I try to connect from an Android device, it gives me an error: 'pairing rejected by BLE shield' or 'couldn't pair with BLE Shield because of an incorrect PIN or passkey'.</p>

<p>What seems to be the problem?</p>
 10394: <p>I would guess that the problem is an incorrect PIN or passkey. </p>

<p>I've read from manuals for some gadgets that some devices/phones automatically try the PIN 0000 and some don't.  I have never seen my Windows phone ask for a PIN when the device hasn't got one set, so I'm guessing that Windows automatically tries 0000 and Android doesn't.  Is there a  setting on Android that will let you enter the pin (which is probably 0000) ?</p>
