I have recently bought a BK8000L audio Bluetooth module. I can't communicate with it via the serial port to configure it using AT commands. The RX and TX pins seem to be being held low. (I would expect the TX pin to be at about + 3 volts with nothing connected to it.) When I connect an FTDI FT232RL (USB to serial module.) to the TX from the FTDI module is pulled down to about 1.4 volts by the RX pin of the bluetooth module. (Before it is connected the FTDI TX line is at about +3.3 volts. I had tried sending AT commands at baud rates from 1200 bauds to 115200 bauds before I realised that the RX and TX pins were being held low without any response. I can pair it with my Nexus 7 and it works in the receive mode but I cannot pair it with Bluetooth headphones to use it in the transmit mode. (Which is why I bought it.) Has any other forum member had any success in using the AT commands with this type of module. I have never had a problem with AT commands with Bluetooth HC-05 or HC-06.
Les.
Les.