is likely a specialized Bluetooth module often integrated into IoT devices

The BL12A3 module has a compact size of 15.6mm x 10.5mm x 2.5mm and 24 pins. The pinout is as follows:

Some variants include pins for hardware flow control, useful at baud rates above 115200 bps.

Unlike proprietary chips from Qualcomm or Broadcom, the BL12A3 is often found in generic, no-name audio adapters, DIY kits, and replacement parts for broken Bluetooth speakers. It is prized for its simplicity: power it with 5V DC, connect it to your amplifier or active speakers, and you are ready to stream.

| Parameter | Value | | :--- | :--- | | | 3.0 + EDR (Enhanced Data Rate) – backwards compatible with 2.1 | | Frequency Band | 2.4 GHz ISM (79 channels) | | Output Power Class | Class 2 (up to 4 dBm) – range approx. 10-15 meters line-of-sight | | Sensitivity | -82 dBm (typical) | | Core Chipset | Broadcom BCM2042 or BCM20730 (variant dependent) | | Interface | UART (TTL levels, 3.3V), PCM for audio, and GPIO | | Profiles Supported | HSP, HFP 1.5, A2DP 1.2, AVRCP 1.4, SPP | | Operating Voltage | 3.0V – 3.6V (absolute max 3.9V – risk of damage) | | Current Consumption | Active TX: 45-55 mA, Sleep: <1 mA | | Antenna Type | On-board PCB trace antenna or u.FL connector | | Form Factor | 16mm x 20mm x 2.3mm (typical) |

BL12A3 Bluetooth Full — Wireless Earbuds with Charging Case