1. The core module uses the slave module. The output interface includes VCC, GND, TXD, RXD, KEY pins, and the Bluetooth connection status pin (STATE). The output is low when not connected, and high after connection.2. LED indicates the bluetooth connection status, fast flashing means no bluetooth connection, slow flashing means entering AT mode, double flashing means bluetooth is connected and the port is open3. The bottom plate is equipped with anti-reverse diode, with 3.3V LDO, the input voltage is 3.6~6V, the current is about 30mA when not paired, and about 10mA after pairing, and the input voltage is prohibited to exceed 7V 4. The interface level is 3.3V, which can be directly connected to various microcontrollers (51, AVR, PIC, ARM, MSP430, etc.), and 5V microcontrollers can also be directly connected, without MAX232 or through MAX232 5. The effective distance in open space is 10 meters ( level is CLASS 2), and it is possible to exceed 10 meters, but the connection quality of this distance is not guaranteedAfter pairing, it can be used as a full-duplex serial port without knowing any Bluetooth protocol. It supports 8-bit data bits, 1-bit stop bit, and a communication format that can be set to parity. This is also a commonly used communication format and does not support other formats.You can enter the AT mode by pulling up pin 34 to set parameters and query informationSmall size (3.57cm*1.52cm), factory patch production to patch quality. And set the transparent heat-shrinkable tube, dust-proof and beautiful, and has a certain anti-static ability.It can be switched to host or slave mode through AT commands, and can be connected to specified devices through AT commands10. Support standard baud rate from 4800bps to 1382400bps.Material: PCBcolour: bluePackageContents:3 x Bluetooth moduleOnly the above package content, other products are not included.Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.