1、The core module uses slave, the leading interface includes VCC, GND, TXD, RXD, reserved LED state output pin, the single‑chip microcomputer can judge whether it has been connected by this foot state, the KEY pin is invalid to the slave machine. 2、LED indicates the connection status, flashing indicates no connection, steady light indicates that is connected and the port is open. 3、Interface electric level is 3.3V, can be directly connected to a variety of microcontrollers (51, AVR, PIC, ARM, MSP430, etc.), 5V microcontroller can also be directly connected, without MAX232 nor through MAX232! 4、The effective distance of the open space is 10 meters, more than 10 meters is also possible, but the quality of the connection is not guaranteed. 5、When paired, it is used as a full‑duplex serial port. It does not need to know any protocol, but only supports 8‑bit data bits, 1‑bit stop bits, and no parity communication format. This is also the most common communication format, and does not support other formats. Features: The core module uses slave, the leading interface includes VCC, GND, TXD, RXD, reserved LED state output pin, the single-chip microcomputer can judge whether it has been connected by this foot state, the KEY pin is invalid to the slave machine. LED indicates the connection status, flashing indicates no connection, steady light indicates that is connected and the port is open. Interface electric level is 3.3V, can be directly connected to a variety of microcontrollers (51, AVR, PIC, ARM, MSP430, etc.), 5V microcontroller can also be directly connected, without MAX232 nor through MAX232! The effective distance of the open space is 10 meters, more than 10 meters is also possible, but the quality of the connection is not guaranteed. When paired, it is used as a full-duplex serial port. It does not need to know any protocol, but only supports 8-bit data bits, 1-bit stop bits, and no parity communication format. This is also the most common communication format, and does not support other formats. When the connection is not established, the baud rate, name, and pairing password can be set by the AT command, and the set parameters are saved after power-off. Automatically switch to transparent mode after connection. Small size, factory patch production, to make sure the quality of the patch. And set of transparent heat-shrinkable tube, dust-proof and beautiful, and has a certain anti-static ability. The product is a slave, and the function is paired with various computers, hosts, most kinds of mobile phones, PDAs, PSPs, and other smart terminals compatible with Bluetooth.Slaves can not pair with each other. Specification: Port: VCC,GND,TXD,RXD Base Board Voltage: 3.3V LDO Input Voltage: 3.6V~6V Unpaired Current: 30mA Paired Current: 10mA Input Voltage:<7V Port Electrical Level: 3.3V Size:37 * 16 * 3mm / 1.46 * 0.63 * 0.12in Weight: 2g/0.07oz Package List: 1* Module Note: 1. After successful self-suppression test, the TXD or RXD is short-circuited to the ground during use. 2. The module is connected to the reverse power supply and causes damage. Users Manual: TXD: The sender is generally represented as its own sender. Normal communication must be connected to the RXD of another device. RXD: The receiving end is generally represented as its own receiving end, and normal communication must be connected to the TXD of another device. In normal communication, the TXD of its own is always connected to the RXD of the device! Self-receiving: RXD is connected to the TXD of other devices during normal communication. Therefore, if you want to receive the data sent by yourself, that is, its TXD is directly connected to RXD, it is the fastest and easiest test to test whether its transmission and reception are normal. Method, when the problem occurs, first do the test to determine if the product is faulty. Loopback test.