I am using ATtiny2313 microcontroller along with a bluetooth module(HC-05) to communicate with my laptop. Heres my doubt, How does the bluetooth module communicate with the laptop. i.e. what is the digital communication format used (whether BASK, manchester ... ?). How do i calculate the baud rate graphically and read what data is being sent from the waveform (i am looking at the waveform on the TX pin of the microcontroller on a DSO). Also, should the waveform be very stable or should it be noisy (i am sending a constant byte 0b01010101 over the bluetooth). If someone can provide me example waveforms, i shall be grateful


Well Bluetooth uses a radio transmitter far faster than your DSO can measure, but the signal from your microcontroller is just standard UART serial signals. They idle high, and the frames are usually a start bit, 8 data bits, and a stop bit.

The baud rate should be very obvious and known, your code in your microcontroller should specifically state what baud rate to send out on the UART on (or some register settings somewhere). If you have the UART signals on DSO, you can see the time between rising or falling edges of the bit transmissions, and this is the time to transmit a single bit. Baud rate is bits per second, so do the math.

The HC-05 is a serial bridge, so with a Bluetooth connection to your laptop you can use any sort of terminal program like PuTTY (and others, I've only used PuTTY though) to connect to the serial port with the same baud rate and you should see the ASCII symbol for 01010101 which in Hex is 0x55 or Decimal 85, and in the ASCII chart this is capital U.

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