To enable the entire system to be as wireless as possible and reduce the number of connections to the PC, while leaving an interface for future mobile control, I chose the HC-05 Bluetooth module (shown below) to transmit serial control commands via Bluetooth. The usage of this module is referenced from “Arduino—HC-05 Bluetooth Module”.
I directly used a serial debugging tool for AT command settings. Here are two points of experience: 1. Before sending AT commands, the EN pin of the module needs to be set to high level; 2. Each command sent must be followed by a carriage return, and if “OK” is echoed back, it indicates that the command was executed successfully.
The AT commands I set and their meanings are:
AT+NAME=Satelite_lite_station Set the Bluetooth access name to “Satelite_lite_station”
AT+ROLE=0 Set Bluetooth to slave mode, i.e., passive connection
AT+PSWD:BG9OXA Set the password
AT+UART:9600,0,0 Set the baud rate to 9600, stop bit 0, no parity
The supply voltage for the HC-05 module is 5V, and the design voltage for the signal receiving pin is 3.3V. Although the product manual states that short-term 5V signal reception is unaffected, long-term transmission may burn out the module. To ensure the entire system operates for an extended period, I designed a simple voltage divider circuit as per the instructions, using two resistors: 10K and 20K. The wiring method is shown below. The calculation method for the resistor values is as follows: the voltage to be divided U = 5V * R2 / (R1 + R2) = 3.3V, working current I = U/R = 5V / (R1 + R2) = 0.16mA. Solving the equation gives R1 ≈ 10K, R2 ≈ 20K.
Once the HC-05 module is successfully configured, it connects to the computer, where the Windows 10 system will virtualize two virtual COM ports (as shown below). After testing, the “outgoing” port is used as the interface for system interaction. This COM port is the serial port used when the Windows system initiates the connection.
