# About Packets
# Packet Structure
# Header LRC
The header LRC (Longitudinal Redundancy Check) provides error checking on the packet header. It also allows the decoder to find the start of a packet by scanning for a valid LRC. Only the lower 8 bits of the calculation below are provided in the LRC field of the packet header. The LRC can be found using the following:
# Packet ID
The packet ID is used to distinguish the contents of the packet. Packet IDs range from 0 to 255. See Advanced Navigation Packet Protocol.
System packets have packet IDs in the range 0 to 19. These packets are implemented the same by every device using ANPP.
State packets are packets that contain data that changes with time, i.e. temperature. State packets can be set to output at a certain rate. State packets are packet IDs in the range 20 to 179.
Configuration packets are used for reading and writing device configuration. Configuration packets are packet IDs in the range 180 to 255.
# Packet Length
The packet length denotes the length of the packet data, i.e. from byte index 5 onwards inclusive. Packet length has a range of 0 – 255.
# Packet Requests
Any of the state and configuration packets can be requested at any time using the Request Packet.
# Packet Acknowledgement
When configuration packets are sent to Boreas, it will reply with an acknowledgement packet that indicates whether the configuration change was successful or not. See Acknowledge Packet.
External data packets will also generate negative acknowledgement packets if there is a problem with the packet. Positive acknowledgements will not be sent. See External Data for a list of External Data Packets.
| ID | 字 段 | 数 据描述 |
| 1 | $--GRS | Log头 |
| 2 | utc | Utc时间 |
| 3 | mode | 模式： 0 = 计算中1 = 计算后 |
| 4 | res | 参与定位解算的卫星的范围残 差，单位米。范围：±999。 如果范围残差超过±99.9，则舍弃 小数部分，取整数（如-103.7 取 - 103） |
| 5 | ||
| 6 | ||
| 7 | ||
| 8 | ||
| 9 | ||
| 10 | ||
| 11 | ||
| 12 | ||
| 13 | ||
| 14 | ||
| 15 | ||
| 16 | Sys id | GNSS系统ID |
| 17 | Signal id | GNSS信号ID |
| 18 | *xx | 校验和 |
| 19 | [CR][LF] | 语句结束符 |
| 位 | 描述 |
| 0 | GNSS状态，见 11.4.4 |
| 1 | |
| 2 | |
| 3 | |
| 4 | 多普勒速度有效位 |
| 5 | 时间有效位 |
| 6 | 外部GNSS |
| 7 | 倾斜有效位 |
| 8 | 航向有效位 |
| 9 | 浮点模糊度航向 |
| 10-15 | 保留 |
| 帧头 | 数据区 | 帧尾 | |||||||
| 起始标志 | 指令类别 | 数据长度 | 流水序号 | 帧头CRC8 | 数据CRC16 | 载荷 | 结束标志 | ||
| 字节数 | 1 | 1 | 1 | 1 | 1 | 2 | 1-255 | 1 | |
| 数值 | 0xFC | A | B | C | D | 高字节(E) | 低字节(E) | 0xFD | |
| paramName | 端口说明 | paramValue | 对应波特率 |
| COMM_BAUD1 | UART,TTL电平,设置范围9600bps- 921600bps | 1 | 9600bps |
| 2 | 19200bps | ||
| 3 | 38400bps | ||
| COMM_BAUD2 | UART,TTL电平,设置范围9600bps- 921600bps | 4 | 76800bps |
| 5 | 115200bps | ||
| 6 | 230400bps | ||
| COMM_BAUD3 | UART,TTL电平,设置范围9600bps- 921600bps | 7 | 460800bps |
| 8 | 921600bps | ||
| 9 | 2625000bps | ||
| COMM_BAUD4 | CAN,可设置波特率为250000bps、 500000bps、1000000bps | 10 | 5250000bps |
| 11 | 10500000bps | ||
| 12 | 100000bps | ||
| 13 | 250000bps | ||
| 14 | 500000bps | ||
| 15 | 1000000bps |
| paramName | 端口说明 | paramValue | 对应波特率 |
| COMM_BAUD1 | RS232，设置范围9600bps- 921600bps | 1 | 9600bps |
| 2 | 19200bps | ||
| 3 | 38400bps | ||
| COMM_BAUD2 | RS232，设置范围9600bps- 921600bps | 4 | 76800bps |
| 5 | 115200bps | ||
| 6 | 230400bps | ||
| COMM_BAUD3 | RS422，设置范围9600bps- 921600bps | 7 | 460800bps |
| 8 | 921600bps | ||
| 9 | 2625000bps | ||
| COMM_BAUD4 | GPIO TTL，设置范围9600bps-921600bps | 10 | 5250000bps |
| 11 | 10500000bps | ||
| 12 | 100000bps | ||
| COMM_BAUD5 | CAN，可设置波特率为250000bps、 500000bps、1000000bps | 13 | 250000bps |
| 14 | 500000bps | ||
| 15 | 1000000bps |
| paramName | 端口协议 | 说明 |
| COMM_STREAM_TYP(1-5) | None | 空 |
| Main | 主串口，默认为串口1，配置为该协议的 串口用于连接上位机和发送FDILink 数据，所 有串口必须且只有一个Main | |
| NAV | 导航协议，配置为该协议的串口用于发送 FDIlink数据，发送数据类型与Main串口相 同，但无法连接上位机 | |
| RTCM | 接收差分数据，有GPS数据的情况下，一般 将串口2配置为该协议，往里面发送D3 00 格式的差分数据，就能实现高精度差分定位 | |
| NMEA | 接收并解析NMEA语句，一般将串口3配置为 该模式，用户需要发送特定的NMEA0183语 句才能实现GNSS/INS组合导航功能，位置 融合至少需要GGA，GSA和GST语句，速度 融合至少需要VTG语句。支持解析的所有 语句为：GGA|GLL|VTG|RMC|GSA|GST|GSV | |
| NMEA(OUT) | 输出NMEA语句，语句里的数据是 GNSS/INS组合后的结果，输出语句类型固 定,具体为可见第12章； 输出频率在上位机配置界面右侧的 MSG_OUT_NMEA框中设置 | |
| Ublox | 接收并解析Ublox语句，一般将串口3配置为 该模式，用户需要发送特定的UBX二进制数 据才能实现GNSS/INS组合导航功能，至少 为UBX-NAV-DOP|UBX-NAV-PVT|UBX- NAV-STATUS|UBX-NAV-TIMEGPS|UBX- NAV_VELNED|UBX-NAV-POSLLH | |
| External XXX | 接收外部数据类型 |
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