The BK1085 is a PLL FM transmitter with 64-125 MHz band, in this example i use an Arduino NANO
and my new BK1085-DEV board.
Even thoug has been used the Nano board, the sourcecode has been compiled with Eclipse and AVR GCC, not Arduino official
IDE and the code is pure C, for the upload i use a USBASP programmer, that wipes out the Arduino bootloader.
The example code simply switches between some stations and pushes a PWM signal inside the R and L inputs
to send noise for a little time on each station, you could connect an audio source.
The project started with a FM car modulator for MP3 music, then i decided to build my development board, you
can see the "history" of my work in the pictures below.
D9 L-CH/R-CH NOISE (+ 470ohm to gnd)
5V 3V3 (power all the system with 3v3)
The MCU has been removed, it provided the clock source so i used a crystal and 2 capacitors for the oscillator.
Then i designed my small DEV board....
Same as the Arduino one here, but this is cheaper. PAY ATTENTION, put 10K resistors between the BT5/BT6 out and the actual buttons or it freeze
the USB stuck, i don't know why but it seems to be a current sink problem, maybe because all the PULL-UPs enabled, but the strange thing
is that these inputs only have the problem.