1.6 KiB
1.6 KiB
Beast protocol
Ports
- 30005: server -> client feed
Format
All data is escaped: 0x1a -> 0x1a 0x1a. Note that synchronization is still
complex, since 0x1a 0x31 may be the start of a frame or mid-data, depending
on what preceded it. To synchronize, you must see, in order:
- !=
0x1a 0x1a- {
0x31,0x32,0x33}
Escaping makes frame length for a given type variable, up to
2 + (2 * data_length_sum)
Frame structure
0x1a- 1 byte frame type (see types below)
- 6 byte MLAT timestamp (see below)
Frame types
0x31: Mode-AC frame- 1 byte signal level (TODO: units?)
- 2 byte Mode-AC data
0x32: Mode-S short frame- 1 byte signal level (TODO: units?)
- 7 byte Mode-S short data
0x33: Mode-S long frame- 1 byte signal level (TODO: units?)
- 14 byte Mode-S long data
0x34: Status data- Appears to only be used by Mode-S Beast hardware later versions
- ?? byte status data
- ?? byte DIP switch configuration
MLAT timestamp
The MLAT timestamp included in each frame is the big-endian value of a 12 MHz counter at the time of packet reception. This counter isn't calibrated to external time, but receiving software can calculate its offset from other receiving stations across multiple packets, and then use the differences between station receive timing to calculate signal source position.