FPGA_HF_READER_MODE_RECEIVE_AMPLITUDE | FPGA_HF_READER_2SUBCARRIERS_424_484_KHZ
flags will return 2 fsk bits (same ones as in sniffing mode: '10' =>
424kHz, '01' => 484kHz, '11' => unknown signal and '00' for no signal
received) in addition to the signal amplitude (on 14 bits) on 424kHz.
switching Fpgamode while sniffing with FpgaWriteConfWord() was
sometimes too long so the tag answer start was lost.
Now, (only with FPGA_BITSTREAM_HF_15) with "FPGA_HF_READER_MODE_SNIFF_AMPLITUDE |
FPGA_HF_READER_2SUBCARRIERS_424_484_KHZ": the amplitude is shrank
from its 2 LSB bits and those 2 bits are now used to return the current
frequency. From my tests, this 2 bits reduction does not affect
quality of 1SC sniffing, but it may have slightly reduced the
receiving range.
FPGA FSK decoding code is also improved.
