4 Packet Format Details

Payload IDs

All of the Horus Binary packet formats use a numerical payload ID instead of a textual callsign. These payload IDs are decoded to a textual callsign during the decoding process through the payload ID list. Users can request their own payload ID by either raising an issue on this repository, or raising a pull request with the required changes.

Payload IDs are shared between the v1 and 16-byte modes, which only have a single-byte payload ID field. The v2 32-byte mode enables a large number of payload IDs, and so payloads using this mode will be allocated IDs > 256 to enable the 0-255 range priority for v1 and 16-byte v2 payloads.

Packet Formats

Horus Binary v1 (22 bytes)

Note: This packet format has now been retired, and the Horus v2 format is now in use.

Byte No.	Data Type	Size (bytes)	Description
0	uint8	1	Payload ID (0-255)
1	uint16	2	Sequence Number
3	uint8	1	Time-of-day (Hours)
4	uint8	1	Time-of-day (Minutes)
5	uint8	1	Time-of-day (Seconds)
6	float	4	Latitude
10	float	4	Longitude
14	uint16	2	Altitude (m)
16	uint8	1	Speed (kph)
17	uint8	1	Satellites
18	int8	1	Temperature (deg C)
19	uint8	1	Battery Voltage
20	uint16	2	CRC16-CCITT Checksum

Horus Binary v2 - 32 byte format

The 32-byte format is the new standard Horus Binary telemetry format. It is based on the 22-byte format above, but with an expanded payload ID field to allow for more unique callsigns, and additional space is available for custom data.

Byte No.	Data Type	Size (bytes)	Description
0	uint16	2	Payload ID (0-65535)
2	uint16	2	Sequence Number
4	uint8	1	Time-of-day (Hours)
5	uint8	1	Time-of-day (Minutes)
6	uint8	1	Time-of-day (Seconds)
7	float	4	Latitude
11	float	4	Longitude
15	uint16	2	Altitude (m)
17	uint8	1	Speed (kph)
18	uint8	1	Satellites
19	int8	1	Temperature (deg C)
20	uint8	1	Battery Voltage
21	???	9	Custom data
30	uint16	2	CRC16-CCITT Checksum

The custom data fields must be described in this json file which will need a new entry added for each new callsign.