HiLetgo 2pcs HC-05 Wireless Bluetooth RF Transceiver Master Slave Integrated Bluetooth Module 6 Pin Wireless Serial Port Communication BT Module f...

I bought two sets of these and could NOT get them configured work at all. I tried all baud rates, with and without newlines, carriage returns, etc. Tried holding EN pin high on power up. Tried different serial terminals and FTDI boards. Nothing. I could enter AT mode but could not get them to even echo the version. Do not buy these.

I was able to communicate between my microcontroller and android phone with these units.

I was able to get these modules to work in peripheral mode at 921600 baud. Below are some notes which apply to ones I purchased in December 2022 with a firmware version 2.0-20100601. The modules have two modes: a configuration mode with AT commands and a serial communication mode for data transfer. When the modules are powered up with the "EN" pin set to 3.3V or the button pressed they blink slowly (about once every 2 seconds) and can be configured with nonstandard AT commands. The speed is always at 38400 baud. The device does not show up for pairing when in this mode. When the modules are powered up with the "EN" pin set to 0V or is left unconnected they blink quickly (about twice a second) and are available for pairing with a default name of HC-05 and a default baud rate of 9600 baud for data communication. To switch between the configuration mode and data communication mode requires cycling power on the device. In the below configuration examples lines that start with # are comments. Also all commands are followed by a carriage return character (ASCII 13) followed by a newline character (ASCII 10). # In configuration mode (slow blink) at 38400 baud I got the version with AT+VERSION # It returned +VERSION:2.0-20100601 OK # To get the UART speed I sent AT+UART # It returned (this was after I set it to 115200 from the default of 9600) +UART:115200,0,0 OK # To set the UART speed for 921600 (1 stop bit, No parity) AT+UART=921600,0,0 # It returned +UART:921600,0,0 OK # To set the name of the device to "CH1" I sent AT+NAME=CH1 # It returned OK # To get the name of the device I sent AT+NAME # It returned NAME:CH1 OK Once configured I cycled power with EN unconnected and it entered the data communication mode (fast blink). I was able to pair with it by finding the device "CH1" using Windows 10. Two COM ports appeared after pairing. The reason for two COM ports is related to RFCOMMs implementation and not this particular device. For me only one of the COM ports worked and its baud rate did not have to match the baud rate programmed into the HC-05 which I had set to 921600. I'm giving the devices four stars because although the firmware is buggy and there is no documentation except for reviewer comments these are the only devices I could get to work at 921600 and I like the button to start in configuration mode and their price point. Similar devices such as the JDY-31 are much slower and lack that feature.

These modules work fine, but are a little quirky. You can get into command mode by holding the button and powering the device up, or by latching the pin called 'EN' to VCC. This is more consistent with what is described other places as the 'KEY' pin rather than the 'EN' pin. The command firmware in the modules I got would constantly repeat the results of the commands until a number of CR/NL were entered. I don't know if this is normal for other HC-05 modules, but it was odd. The commands will take, but 'AT' and the like will not echo. The assemble quality was sloppy. The bluetooth module and controller is actually attached to a breakout board and the alignment of the module to the breakout board was twisted in a 3 of the 4 I got. Everything still works, just sloppy, but for the price this isn't a big complaint.

Tested and working very well.