Your BT module works on 3.3V | Microcontroller › AVR › Problems with RS-232 Interfacing › Your BT module works on 3.3V April 18, 2012 at 1:18 pm #7480 AJISH ALFREDParticipant Your BT module works on 3.3V and it gives 0 for low bit and 3.3V for high bit. It will cause issues while connecting with 5V ttl logic. Use a 3.3V to 5V level shifter before connecting it with the controller
