I need help solving a mystery.
I can not send commands (serial) to the DFPlayer mp3 module. The format of the commands is in hex, two of them, consisting of checksum, according to the example (Arduino) below:
checksum = FF+06+0E+00+00+00=113(in hex)
checksum = 0 - checksum=0-113(113 is hex data)=FFFFFFFEED
then 4 end words is your checksum
checksum = 0 - (0xFF+0x06+0x0E+0x00+0x00+0x00)
checksum = -275 ??
Another problem that is occurring is that the module, once it is turned on, should send (serial) a status phrase in hex [7E FF 06 3F 00 00 02 xx xx EF], but it does not work.