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.
Features: This small size Bluetooth 4.0 transceiver module allows your device communicate with IOS Android, Arudino and others. You can set it as slave or master. You can use AT command set the baud rate. Ultra-low standby power consumption 90uA-400uA, built in PCB antenna, has a built-In Level Switch Function. The CC2541 is highly suited for systems where ultra low power consumption is required. This is specified by various operating modes. Short transition times between operating modes further enable low power consumption.
Specifications: Input Voltage: DC 3.3V/5V Input voltage : 3.3V/5V