Summary of the article without talking nonsense:
Directly connecting PWLINK and HC-05 cannot enter AT mode because the VCC of the Bluetooth module can only be connected to 5V and cannot be connected to 3.3V, and PWLINK has two VDD pins, and the initial default output voltage of both VDD pins is 3.3 V, so you need to change the output from 3.3V to 5V to enter the AT mode of HC-05 normally.
Detailed description:
When debugging HC-05, there are many people on the Internet who use USB to TTL for AT mode debugging, but I only bought the PWLINK2 debugger, so I asked the official customer service of Chuangxin Workshop: So I referred to the Bluetooth module and USB TO
TTL
. Wiring method: Wire PWLINK to the Bluetooth module.
PWLINK is also connected to HC-05 with 4 wires. The only difference from the picture above is that PWLINK uses one of its VDD pins to connect to the VCC pin of HC-05. After connection, press and hold HC -05 button, then connect to the computer and power on. Enter below:
video_20230423_221538
Obviously, this is not the correct way to enter AT mode, because the light stops flashing after flashing quickly. . .
Precautions for using HC-05 products given by Taobao merchants:
The LED indicates the Bluetooth connection status. Flashing quickly indicates that there is no Bluetooth connection. Flashing slowly indicates entering AT mode. Double flashing indicates that Bluetooth is connected and the port is open. 2. Wiring
If you want to enter AT mode, keep pressing the button until the setting is completed.
Notice:The VCC of the Bluetooth module can only be connected to 5V, not 3.3V!3. Test
First press and hold the button on the HC05 Bluetooth module, and then power on the Bluetooth module. The LED on the Bluetooth module enters slow flashing mode (flashes once in about 1 second), and you can perform AT command testing. The AT command
format is: baud rate 38400, 8 data bits, 1 stop bit, no parity. After each command is entered, you must press the Enter key before sending!
For example: input AT, press the Enter key to send, the Bluetooth module will return OK
① How to modify the Bluetooth module to host mode:
input AT+ROLE=1 and then press the Enter key to send, the Bluetooth module will return OK, indicating that the modification is successful! After powering off, the Bluetooth module will be in master mode and automatically search for surrounding slaves. If you
input AT+ROLE=0, it will be changed to slave mode. (Note: The default is slave mode, no need to modify)
②How to modify the Bluetooth module name:
Enter AT+NAME=Beijin and press the Enter key to send, Bluetooth returns OK, indicating that the Bluetooth name is changed to Beijing
③How to modify the Bluetooth module pairing password :
Enter AT+PSWD=2222 and press the Enter key to send. Bluetooth returns OK, indicating that the Bluetooth pairing password has been changed to 2222.
④How to modify the communication baud rate (Note: The baud rate in AT mode is 38400, and the baud rate during normal communication is is 9600):
Enter AT+UART=115200, 1, 2 and then press the Enter key to send. Bluetooth returns OK, indicating that the Bluetooth communication baud rate is modified to 115200, 2 stop bits, Even verification (Note: Default communication parameters is 9600,0,0)
Warm reminder:
1.The supply voltage must be 5V, not 3.3V
2. Do not connect the power cord pins to the data lines. Please confirm carefully before wiring.
3. The LED must enter slow flash mode before AT command testing can be performed.
4. After each AT command input is completed, you must click Return. 5. If it cannot return
OK, please exchange RXD and TXD.
6. Do not tear off the heat shrink tube or weld it yourself, otherwise it will be regarded as giving up the warranty and return and exchange services.
7. RXD and TXD on UNO cannot be used. Connect Bluetooth module for AT command test
After checking the information, I found that pwlink2 can output two voltages, 3.3v or 5v, but the two VDD pins output the same voltage value. One cannot be set to output 3.3v and the other to output 5v. There are experts on the Internet who rewire pwlink. After processing, it can have one 3.3v and one 5v, but I only need to make it output 5v, so it does not enter the AT mode normally, indicating that the output pin of PWLINK may not be 5v. Configuring the voltage output of PWLINK can be configured in software.
Open the burning software provided by pwlink, just opened it. You will find that the default level output is 3.3v, and what we need is 5v. We need to change the interface level to 5v.
Things look like this when reconnecting:
video_20230423_222154
After entering the AT mode of HC-05, we need to disconnect the pwlink software, otherwise when we use other serial port debugging tools, there will be a warning that the serial port is occupied by pwlink, as follows (the burning software supporting pwlink also has the function of the serial port, but I haven’t figured out how to use it)
After disconnecting, HC-05 is still in AT mode.
At this time, when I go to debug, everything is normal.
