![]() Note that I use the configuration above (I've called it nf). ![]() For simplicity, I omit the tail command to skip the header. We can play the WAV files into direwolf to decode them. The MODEM line declares a 1000baud modem using tones at 1000Hz and 1833Hz with three different decoding algorithms (A, B and C) running in parallel. The ARATE sets the audio rate to 48kHz, matching the rate of the WAV files. ![]() We will use the following configuration file for direwolf: It is an open source modem with a superb decoder and many other functionalities, such as APRS and digipeater. ![]() One of my favourite tools for packet radio is direwolf. The only differences are that the baudrate is 1000baud instead of 1200baud and the AFSK tones are 1000Hz and 1833.33Hz instead of the standard 1200Hz and 2200Hz. The modulation and coding used by the commands is very similar to the standard 1k2 Amateur packet radio. The WAV header will be interpreted as sound samples, but this doesn't really disturb anything. The tail command here is used to skip the WAV header, which is 44 bytes long. However, several tools such as Audacity refuse to open the files. They are 48kHz WAV files containing uint8_t samples. The first thing to note is that there seems to be some problem with the header of the WAV files produced Wei. Here I look at the contents of these WAV files and how to process and create this kind of packets. For ease of use, he also gives WAV recordings of the three commands, so they can be played back easily into an FM transmitter by any Amateur. The AX.25 frames are UI frames containing a single byte with the command ( 0x00, 0x55 or 0xaa as described above). They use AX.25 with 1000baud FM-AFSK with tones at 1000Hz and 1833.33Hz. ![]() He also gives the modulation and coding details for the commands. Essentially, there are three commands that can be used: 0x00 to take a picture and send it, 0x55 to take a picture and store it in memory, and 0xaa to send the picture stored in memory. Recently, Wei BG2BHC has published instructions for the use of BY70-1's camera by Amateurs. ![]()
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