| Offset | Length | Field | Encoding |
|---|
0x00 | 2 | Header | AA 55 |
0x02 | 1 | Length | Bytes from family through the end of data |
0x03 | 1 | Leading byte | 00 |
0x04 | 1 | family | Command family |
0x05 | 1 | command | Command number |
0x06 | N | data | Command data |
| Variable | 2 | CRC | little-endian |
| Variable | 2 | Tail | 77 EE |
The length field excludes the leading 00. CRC input starts at family and ends at the last data byte.
| Parameter | Value |
|---|
| Algorithm | CRC-16/CCITT-FALSE |
| Polynomial | 0x1021 |
| Init | 0x1234 |
| RefIn | false |
| RefOut | false |
| Output byte order | little-endian |
| family | Direction | Meaning |
|---|
01 | Host to device | Query |
02 | Host to device | Setting or data transmission |
81 | Device to host | Query response or status report |
82 | Device to host | Setting acknowledgment |
A received frame may omit the leading 00. In that form, the length directly covers family, command, and data. The CRC input remains unchanged.