I connected Arduino pro mini 5V/16MHz with sparkfun silvermate (Bluetooth) and can transfer data without any issue. However, if I use 3.3V/8MHz (ATmega328). I can not communicate bluetooth. Basically bluetooth read giberish.
I also tested increasing pro mini's voltage with 3.8V. I found Tx pin of bluetooth increases at same level. However, Rx pin stays at 3.27V. I am not sure this is the reason.
I am simply trying to find a solution here. If any one can help me that will be great.