Some time ago I've acquired a cheap Bluetooth UART module. It's labelled "CZ-HC-05 gomcu".
The PINs are, top to bottom
To change the settings of the device, I connected the module as follows to my CP2102 USB serial adapter: 5V=VCC, TXC=TXD, RXC=RXD, GND=GND
Note that TX and RX are connected in an unusual manner. You might need to swap them for your adapter. I'm not sure about that...
As far as I can tell, the KEY and LED pins don't matter for getting in configuration mode. You should not have a device connected via bluetooth.
Afterwards I connected the USB adapter to my computer and ran
sudo dterm 8 n 1 38400 maplf crlf /dev/ttyUSB0
Now I was able to communicate with the bluetooth device with these commands: