参考资料：

https://e2e.ti.com/support/wireless_connectivity/bluetooth_low_energy/f/538/t/457958

问题：

配对时提示密码或PIN错误，但是根本就没有到输入密码这一步，就直接说密码错误了。

环境：

android 6.0，CC254x，协议栈：V1.4.0

原因：

Check remote LMP version before enabling secure connections Request remote version information for LE links when connecting and ensure LMP version is >= 8 (Bluetooth 4.2) before setting the LinkKey bits in the pairing request. This is to ensure older remote devices do not get confused by the additional bit(s) in the pairing request.
"
This change, when incorporated by the respective phone/tablet manufacturers, will ensure BLE 1.4.0 (and previous releases) are compatible with Android6 / BT4.2. All CC254x SW (e.g. BLE 1.4.0) will report an LMP version of 6 (BT4.0).

解决办法：

升级协议栈的V1.4.1。

不过android6.0.1（2015.12.9 Nexus 5）似乎解决了这个bug。

Peripherals that are Pairing with Android devcies that do not yet incorporate this change will need BLE 1.4.1 to remain compatible with smart devices that implement LE Secure Connections (BT4.2) Pairing.