For HC-04, HC-05, HC-06 Bluetooth adapters which are built on CSR BC03 and BC04 (BlueCore 3/4) chipsets, there is a custom firmware available.
It allows to configure Bluetooth module settings via the Bluetooth interface without the requirement to set mode (PIN34/PIO11/KEY) pin high of the module during powering on.
To enter this configuration mode, the first command after establishing Bluetooth connection has to be AT+CONF. It is required to send this in one telegram, in capital letters and terminated by <CR><LF>.
Examples of terminal programs that support this feature:
The firmware supports following CSR compatible command list:
AT: Simply responds with OK.AT+ADDR: Displays the MAC address of the module. You can only read the current setting. To change the MAC address you have to use PSTool.exe from CSR BlueSuite.AT+ORGL: Performs factory reset of the settings (will become active immediately) to Baud rate=115200 8N1, Name=Deep OBD, PIN=1234.AT+RESET: Reboots firmware of the Bluetooth module without changing any settings.AT+DATA: Exits the configuration mode and switches Bluetooth interface back to transparent data mode.AT+PSWD?: Displays the Bluetooth PIN. The response is +PSWD:<pin>.AT+PSWD=<pin>: Write the Bluetooth PIN. The minimum pin length is 4 and the maximum length is 16 digits.AT+NAME?: Displays the Bluetooth name. The response is +NAME:<name>.AT+NAME=<name>: Write the the Bluetooth name. The maximum name length is 31 chars.AT+UART?: Displays the UART settings. The response is +UART:<baud rate>,<stop bits>,<parity>. Possible baud rate values are: 9600, 19200, 38400, 57600, 115200, 230400, 460800, 921600, 1382400. The coding for stop bits is: 0=1 stop bit, 1=2 stop bits and the coding for parity is: 0=None, 1=Odd, 2=Even.AT+UART=<baud rate>,<stop bits>,<parity>: Sets UART settings (will become active immediately).AT+VERSION?: Displays the firmware version. The response is +VERSION:<version>.AT+FWUPDATE: Switches module to firmware update mode via UART interface using the BlueSuite tool DfuWizard. The interface setting in this mode is BCSP 115200 8N1.