AT-09 BLE Bluetooth 4.0 Module TI CC2541 (HM-10)

The AT-09 is a module that contains a BLE chip (a CC2540/CC2541). This module allows to perform serial communication with the BLE chip thanks to an Rx and a Tx pin. This module is also very similar to the HM-10 module and is also compatible with it. So if you have some experience with the latter, you will get started quickly with the AT-09.

Here's a detailed tutorial from Yassine benabbas