Anti Reverse Connection Wireless Bluetooth Serial Port Transmission Module HC-05 Master-slave Integrated Expansion BoardItem NO.: HC-05

HC-05 Bluetooth Serial Port Transmission Module

1.1 Common Sense (Very Important):

● TXD: The sending end, usually represented as its own sending end, must be connected to another device's RXD for normal communication.

● RXD: The receiving end, usually represented as its own receiving end, must be connected to another device's TXD for normal communication.

● During normal communication, the TXD itself is always connected to the RXD of the device!

● Self receiving spontaneity: During normal communication, the RXD is connected to the TXD of other devices. Therefore, if you want to receive the data you send, as the name suggests, it means that you receive the data you send. That is, your own TXD is directly connected to the RXD to test whether your transmission and reception are normal. This is a fast and simple testing method. When problems occur, you should first perform this test to determine whether the product is faulty. Also known as loop back testing.

1.2 Level Logic:

● TTL level: Usually, data representation is binary, with+5V equivalent to logic "1" and 0V equivalent to logic "0". It is called a TTL signal system and is a positive logic

● RS232 level: using -12V to -3V, equivalent to logic "0",+3V to+12V logic level, equivalent to logic "1", is negative logic

1.3 Product Characteristics:

1. The core module uses HC-05 slave module, with output interfaces including VCC, GND, TXD, RXD, KEY pin, Bluetooth connection status output pin (STATE). The output is low when not connected, but high when connected

2. LED indicates Bluetooth connection status, fast flashing indicates no Bluetooth connection, slow flashing indicates entering AT mode, and double flashing indicates Bluetooth is connected and the port is open

3. The base plate is equipped with an anti reverse diode with 3.3V LDO, with an input voltage of 3.6-6V. When not paired, the current is about 30mA, and after pairing, it is about 10mA. The input voltage must not exceed 7V!

4. The interface level is 3.3V, which can be directly connected to various microcontrollers (51, AVR, PIC, ARM, MSP430, etc.). 5V microcontrollers can also be directly connected, without the need for MAX232 and cannot pass through MAX232!

5. The effective distance in an open area is 10 meters (class 2 power level), and exceeding 10 meters is also possible, but there is no guarantee of the connection quality for this distance

6. After pairing, when using a full duplex serial port, there is no need to understand any Bluetooth protocol. It supports 8-bit data bits, 1-bit stop bits, and a communication format that can set parity. This is also a commonly used communication format and does not support other formats.

7. You can set parameters and query information by raising the 34 pin to enter AT command mode

8. Compact in size (3.57cm * 1.52cm), factory produced SMT to ensure SMT quality. And a transparent heat shrink tube is installed, which is dustproof and aesthetically pleasing, and has a certain degree of anti-static ability.

9. You can switch to host or slave mode through the AT command, and connect to specified devices through the AT command

10. Supports standard baud rates from 4800bps to 1382400bps

1.4 Product Usage:

After pairing, it only needs to be used as a fixed baud rate serial port, so as long as the serial port device is in the communication format of "fixed baud rate, 8-bit data, no parity", it can directly replace the original wired serial port without modifying the program. Such as data collection, smart cars, serial printers, outdoor dot matrix strip screen control, etc.

● Paired with a computer: suitable for communication between computers and devices through Bluetooth serial port, using the same method as serial port

● Paired with mobile phones: suitable for communication between mobile phones and devices through Bluetooth serial port, using the same method as serial port

● Paired with Bluetooth host: Suitable for two devices to communicate directly through Bluetooth serial port, such as between microcontroller and microcontroller, wired serial port and microcontroller, etc. The usage method is the same as serial port

1.5 Versatile Use:

Baud rate conversion, as both the receiving and sending ends can choose their own baud rates, can be used as a device for baud rate conversion when the data volume is small.