The AT-09 Bluetooth 4.0 BLE module (popular on AliExpress) is a low‑energy, modern alternative to classic Bluetooth modules like HC‑05 and HC‑06. It is based on the Texas Instruments CC2541 chip, which supports Bluetooth 4.0 (Bluetooth Low Energy / BLE). Unlike the HC series (Bluetooth 2.0), the AT‑09 is designed for low power consumption, making it ideal for battery‑powered IoT devices, wearables, and smartphone apps that use BLE (iOS and Android). The module can operate as both master and slave, and is configurable via AT commands through a UART interface. Most versions on AliExpress come without a push button, but some variants include a small reset button or a button to enter AT command mode. The AT‑09 is pin‑compatible with the HC‑05/HC‑06 (4 pins: VCC, GND, TX, RX) and adds an extra STATE pin for connection status.

Typical applications include:

• Smartphone‑connected fitness trackers / heart rate monitors
• Low‑power wireless sensor nodes (temperature, humidity, motion)
• BLE beacon / proximity detection systems
• Smart locks and door access control (long battery life)
• Wireless game controllers (low latency BLE HID mode)
• IoT home automation (smart plugs, light bulbs, switches)
• Medical devices (glucose meters, pulse oximeters)
• Apple iBeacon or Eddystone compatible projects

Key specifications:

• Chipset: Texas Instruments CC2541 (Bluetooth 4.0 BLE, single‑mode)
• Bluetooth version: 4.0 (BLE) – not backward compatible with Bluetooth 2.0/3.0
• Roles: Master, slave, or beacon (configurable via AT commands)
• Operating voltage: 3.3 V – 6 V (onboard 3.3 V regulator, 5 V tolerant on VCC)
• Logic level: 3.3 V (⚠️ 5 V on RX/TX may damage module – use level shifter)
• Default baud rate: 9600 bps (configurable up to 115200 bps)
• Power consumption: Extremely low – ~8 mA active, ~0.4 µA sleep mode
• Range: ≈30 meters (open air, Class 2)
• AT command mode: Send "AT" over UART (no button needed on most variants)
• Onboard LED: Blue LED flashes in different patterns (disconnected, connected, advertising)
• Interface: 6 pins (VCC, GND, TX, RX, STATE, BRK) – standard 0.1" pitch
• Default pairing PIN: None (BLE uses bonding instead of classic PIN)

✅ Ready to upgrade to Bluetooth 4.0 BLE? The AT‑09 is the perfect choice for low‑power, modern smartphone connectivity. It works seamlessly with nRF Connect, LightBlue, or any BLE‑compatible app on iOS and Android. Order your AT‑09 module today from our trusted AliExpress link – you'll get genuine CC2541 chips, fast shipping, and unbeatable prices. Say goodbye to high power draw and hello to BLE efficiency!

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