Bluetooth HC-05

1.1 tips (very important):
TXD: Send side, generally expressed as their own sender, normal communication must be connected to another device RXD.
RXD: the receiver, generally designated himself on the receiving end, normal communication TXD must be connected to another device.
When normal communication itself TXD RXD always connected device!
Since the resumption of spontaneous: RXD when normal communication TXD connected to other devices, so if you want to receive data sent by itself as the name suggests, is to receive the data they transmit their own, that is directly connected to its own TXD RXD, used to send and receive test itself It is normal, is the quickest and easiest way to test when there is a problem to do the first test to determine whether a product failure. Also known as the loopback test.

1.2 level logic:
TTL level: typically binary data representation, + 5V equivalent to a predetermined logical "1", 0V is equivalent to logic "0", referred to as a TTL signal system, is positive logic
RS232 level: the use of -12V to -3V, equivalent to a logical "0", + 3V to + 12V logic level, equivalent to a logical "1" is negative logic

1.3 Product Features:
1 Core module uses HC-05 from the module, leads to interface includes VCC, GND, TXD, RXD, KEY pin, pin-out Bluetooth connection status (STATE), low output is not connected, the connection of high output
2, led Indicates Bluetooth connection status, Bluetooth connectivity means no flash, slow flash that enter the AT mode, double flash indicates Bluetooth connection and open ports
3, bottom set anti-reverse diode with 3.3V LDO, input voltage 3.6 ~ 6V, when the unpaired current is about 30mA, paired about 10mA, the input voltage must not exceed 7V!
4, interface level 3.3V, can be directly connected to various SCM (51, AVR, PIC, ARM, MSP430, etc.), 5V microcontroller can also be connected directly, without MAX232 MAX232 can not go through!
5, open to the effective distance of 10 meters (power rating of CLASS 2), more than 10 meters are possible, but do not make this connection to ensure the quality of distance
6, after the pair when full-duplex serial interface, without having to know any Bluetooth protocol, supports 8 data bits, 1 stop bit, parity communication format can be set, which is the most common communication format does not support other formats.
7, can be pulled 34 feet into the AT command mode setting parameters and query information
8, small size (3.57cm * 1.52cm), factory chip production to ensure the quality of the patch. Transparent shrink tube and sleeve, dust and beautiful, and there is a certain anti-static capabilities.
9, can be selected via AT command as master or slave mode, can be connected to the specified device through AT commands
10, support from inter-standard baud rate of 4800bps ~ 1382400bps

1.4 Product use:
After pairing only as a fixed baud rate of the serial port can be used in the same, so long as it is "fixed baud, 8 data bits, no parity" communication format serial devices can be directly replace the original wired and serial You do not need to modify the program. Such as data acquisition, smart car, serial printers, and other outdoor dot matrix screen control.
Paired with a computer: for inter-computer communication with the device via Bluetooth serial port, use the same serial port
Paired with the phone use: for between your phone with a Bluetooth device via serial communications, use the same serial port
Paired with a Bluetooth host: for two devices directly via Bluetooth serial communication, such as between the microcontroller and microcontroller serial cable with microchips, etc., use the same serial port