1. 源由

为了将折腾2~3天OpenIPC摄像头Ardupilot配置问题整理下，给各位即将碰到，尚未碰到的朋友准备一份小礼品！

OpenIPC FPV摄像头是一个非常原型的开源数字FPV摄像头，有着非常弹性的功能扩展可能性。并且也希望大家能够轻松上手，少折腾，当然如果有机会，可以往产品化方向落地。

• The OSD icon has not changed at all #53

2. 问题

在《OpenIPC开源IPC之固件sysupgrade升级》中，其实已经提到了为什么要升级固件，主要原因是怀疑兼容性问题。

==》其实，并不是兼容性问题，而是Ardupilot的配置问题。

3. 分析

vdec内部OSD状态变量主要来自MAVLink命令：

• MAVLINK_MSG_ID_RAW_IMU
• MAVLINK_MSG_ID_SYS_STATUS
• MAVLINK_MSG_ID_BATTERY_STATUS
• MAVLINK_MSG_ID_RC_CHANNELS_RAW
• MAVLINK_MSG_ID_GPS_RAW_INT
• MAVLINK_MSG_ID_VFR_HUD
• MAVLINK_MSG_ID_GLOBAL_POSITION_INT
• MAVLINK_MSG_ID_ATTITUDE

3.1 MAVLINK_MSG_ID_RAW_IMU

MAVLink传递结构体：

#define MAVLINK_MSG_ID_RAW_IMU 27MAVPACKED(
typedef struct __mavlink_raw_imu_t {uint64_t time_usec; /*< [us] Timestamp (UNIX Epoch time or time since system boot). The receiving end can infer timestamp format (since 1.1.1970 or since system boot) by checking for the magnitude of the number.*/int16_t xacc; /*<  X acceleration (raw)*/int16_t yacc; /*<  Y acceleration (raw)*/int16_t zacc; /*<  Z acceleration (raw)*/int16_t xgyro; /*<  Angular speed around X axis (raw)*/int16_t ygyro; /*<  Angular speed around Y axis (raw)*/int16_t zgyro; /*<  Angular speed around Z axis (raw)*/int16_t xmag; /*<  X Magnetic field (raw)*/int16_t ymag; /*<  Y Magnetic field (raw)*/int16_t zmag; /*<  Z Magnetic field (raw)*/uint8_t id; /*<  Id. Ids are numbered from 0 and map to IMUs numbered from 1 (e.g. IMU1 will have a message with id=0)*/int16_t temperature; /*< [cdegC] Temperature, 0: IMU does not provide temperature values. If the IMU is at 0C it must send 1 (0.01C).*/
}) mavlink_raw_imu_t;

OSD全局变量：

telemetry_raw_imu = imu.temperature;

3.2 MAVLINK_MSG_ID_SYS_STATUS

MAVLink传递结构体：

#define MAVLINK_MSG_ID_SYS_STATUS 1MAVPACKED(
typedef struct __mavlink_sys_status_t {uint32_t onboard_control_sensors_present; /*<  Bitmap showing which onboard controllers and sensors are present. Value of 0: not present. Value of 1: present.*/uint32_t onboard_control_sensors_enabled; /*<  Bitmap showing which onboard controllers and sensors are enabled:  Value of 0: not enabled. Value of 1: enabled.*/uint32_t onboard_control_sensors_health; /*<  Bitmap showing which onboard controllers and sensors have an error (or are operational). Value of 0: error. Value of 1: healthy.*/uint16_t load; /*< [d%] Maximum usage in percent of the mainloop time. Values: [0-1000] - should always be below 1000*/uint16_t voltage_battery; /*< [mV] Battery voltage, UINT16_MAX: Voltage not sent by autopilot*/int16_t current_battery; /*< [cA] Battery current, -1: Current not sent by autopilot*/uint16_t drop_rate_comm; /*< [c%] Communication drop rate, (UART, I2C, SPI, CAN), dropped packets on all links (packets that were corrupted on reception on the MAV)*/uint16_t errors_comm; /*<  Communication errors (UART, I2C, SPI, CAN), dropped packets on all links (packets that were corrupted on reception on the MAV)*/uint16_t errors_count1; /*<  Autopilot-specific errors*/uint16_t errors_count2; /*<  Autopilot-specific errors*/uint16_t errors_count3; /*<  Autopilot-specific errors*/uint16_t errors_count4; /*<  Autopilot-specific errors*/int8_t battery_remaining; /*< [%] Battery energy remaining, -1: Battery remaining energy not sent by autopilot*/uint32_t onboard_control_sensors_present_extended; /*<  Bitmap showing which onboard controllers and sensors are present. Value of 0: not present. Value of 1: present.*/uint32_t onboard_control_sensors_enabled_extended; /*<  Bitmap showing which onboard controllers and sensors are enabled:  Value of 0: not enabled. Value of 1: enabled.*/uint32_t onboard_control_sensors_health_extended; /*<  Bitmap showing which onboard controllers and sensors have an error (or are operational). Value of 0: error. Value of 1: healthy.*/
}) mavlink_sys_status_t;

OSD全局变量：

telemetry_battery = bat.voltage_battery;
telemetry_current = bat.current_battery;

3.3 MAVLINK_MSG_ID_BATTERY_STATUS

MAVLink传递结构体：

#define MAVLINK_MSG_ID_BATTERY_STATUS 147MAVPACKED(
typedef struct __mavlink_battery_status_t {int32_t current_consumed; /*< [mAh] Consumed charge, -1: autopilot does not provide consumption estimate*/int32_t energy_consumed; /*< [hJ] Consumed energy, -1: autopilot does not provide energy consumption estimate*/int16_t temperature; /*< [cdegC] Temperature of the battery. INT16_MAX for unknown temperature.*/uint16_t voltages[10]; /*< [mV] Battery voltage of cells 1 to 10 (see voltages_ext for cells 11-14). Cells in this field above the valid cell count for this battery should have the UINT16_MAX value. If individual cell voltages are unknown or not measured for this battery, then the overall battery voltage should be filled in cell 0, with all others set to UINT16_MAX. If the voltage of the battery is greater than (UINT16_MAX - 1), then cell 0 should be set to (UINT16_MAX - 1), and cell 1 to the remaining voltage. This can be extended to multiple cells if the total voltage is greater than 2 * (UINT16_MAX - 1).*/int16_t current_battery; /*< [cA] Battery current, -1: autopilot does not measure the current*/uint8_t id; /*<  Battery ID*/uint8_t battery_function; /*<  Function of the battery*/uint8_t type; /*<  Type (chemistry) of the battery*/int8_t battery_remaining; /*< [%] Remaining battery energy. Values: [0-100], -1: autopilot does not estimate the remaining battery.*/int32_t time_remaining; /*< [s] Remaining battery time, 0: autopilot does not provide remaining battery time estimate*/uint8_t charge_state; /*<  State for extent of discharge, provided by autopilot for warning or external reactions*/uint16_t voltages_ext[4]; /*< [mV] Battery voltages for cells 11 to 14. Cells above the valid cell count for this battery should have a value of 0, where zero indicates not supported (note, this is different than for the voltages field and allows empty byte truncation). If the measured value is 0 then 1 should be sent instead.*/uint8_t mode; /*<  Battery mode. Default (0) is that battery mode reporting is not supported or battery is in normal-use mode.*/uint32_t fault_bitmask; /*<  Fault/health indications. These should be set when charge_state is MAV_BATTERY_CHARGE_STATE_FAILED or MAV_BATTERY_CHARGE_STATE_UNHEALTHY (if not, fault reporting is not supported).*/
}) mavlink_battery_status_t;

OSD全局变量：

telemetry_current_consumed = batt.current_consumed;

3.4 MAVLINK_MSG_ID_RC_CHANNELS_RAW

MAVLink传递结构体：

#define MAVLINK_MSG_ID_RC_CHANNELS_RAW 35typedef struct __mavlink_rc_channels_raw_t {uint32_t time_boot_ms; /*< [ms] Timestamp (time since system boot).*/uint16_t chan1_raw; /*< [us] RC channel 1 value.*/uint16_t chan2_raw; /*< [us] RC channel 2 value.*/uint16_t chan3_raw; /*< [us] RC channel 3 value.*/uint16_t chan4_raw; /*< [us] RC channel 4 value.*/uint16_t chan5_raw; /*< [us] RC channel 5 value.*/uint16_t chan6_raw; /*< [us] RC channel 6 value.*/uint16_t chan7_raw; /*< [us] RC channel 7 value.*/uint16_t chan8_raw; /*< [us] RC channel 8 value.*/uint8_t port; /*<  Servo output port (set of 8 outputs = 1 port). Flight stacks running on Pixhawk should use: 0 = MAIN, 1 = AUX.*/uint8_t rssi; /*<  Receive signal strength indicator in device-dependent units/scale. Values: [0-254], UINT8_MAX: invalid/unknown.*/
} mavlink_rc_channels_raw_t;

OSD全局变量：

telemetry_rssi = rc_channels_raw.rssi;
telemetry_throttle = (rc_channels_raw.chan4_raw - 1000) / 10;
telemetry_arm = rc_channels_raw.chan5_raw;
telemetry_resolution = rc_channels_raw.chan8_raw;    // used for resolution script, like a trigger

3.5 MAVLINK_MSG_ID_GPS_RAW_INT

MAVLink传递结构体：

#define MAVLINK_MSG_ID_GPS_RAW_INT 24MAVPACKED(
typedef struct __mavlink_gps_raw_int_t {uint64_t time_usec; /*< [us] Timestamp (UNIX Epoch time or time since system boot). The receiving end can infer timestamp format (since 1.1.1970 or since system boot) by checking for the magnitude of the number.*/int32_t lat; /*< [degE7] Latitude (WGS84, EGM96 ellipsoid)*/int32_t lon; /*< [degE7] Longitude (WGS84, EGM96 ellipsoid)*/int32_t alt; /*< [mm] Altitude (MSL). Positive for up. Note that virtually all GPS modules provide the MSL altitude in addition to the WGS84 altitude.*/uint16_t eph; /*<  GPS HDOP horizontal dilution of position (unitless * 100). If unknown, set to: UINT16_MAX*/uint16_t epv; /*<  GPS VDOP vertical dilution of position (unitless * 100). If unknown, set to: UINT16_MAX*/uint16_t vel; /*< [cm/s] GPS ground speed. If unknown, set to: UINT16_MAX*/uint16_t cog; /*< [cdeg] Course over ground (NOT heading, but direction of movement) in degrees * 100, 0.0..359.99 degrees. If unknown, set to: UINT16_MAX*/uint8_t fix_type; /*<  GPS fix type.*/uint8_t satellites_visible; /*<  Number of satellites visible. If unknown, set to UINT8_MAX*/int32_t alt_ellipsoid; /*< [mm] Altitude (above WGS84, EGM96 ellipsoid). Positive for up.*/uint32_t h_acc; /*< [mm] Position uncertainty.*/uint32_t v_acc; /*< [mm] Altitude uncertainty.*/uint32_t vel_acc; /*< [mm] Speed uncertainty.*/uint32_t hdg_acc; /*< [degE5] Heading / track uncertainty*/uint16_t yaw; /*< [cdeg] Yaw in earth frame from north. Use 0 if this GPS does not provide yaw. Use UINT16_MAX if this GPS is configured to provide yaw and is currently unable to provide it. Use 36000 for north.*/
}) mavlink_gps_raw_int_t;

OSD全局变量：

telemetry_sats = gps.satellites_visible;
telemetry_lat = gps.lat;
telemetry_lon = gps.lon;telemetry_lat_base
telemetry_lon_base
telemetry_distance

3.6 MAVLINK_MSG_ID_VFR_HUD

MAVLink传递结构体：

#define MAVLINK_MSG_ID_VFR_HUD 74typedef struct __mavlink_vfr_hud_t {float airspeed; /*< [m/s] Vehicle speed in form appropriate for vehicle type. For standard aircraft this is typically calibrated airspeed (CAS) or indicated airspeed (IAS) - either of which can be used by a pilot to estimate stall speed.*/float groundspeed; /*< [m/s] Current ground speed.*/float alt; /*< [m] Current altitude (MSL).*/float climb; /*< [m/s] Current climb rate.*/int16_t heading; /*< [deg] Current heading in compass units (0-360, 0=north).*/uint16_t throttle; /*< [%] Current throttle setting (0 to 100).*/
} mavlink_vfr_hud_t;

OSD全局变量：

telemetry_gspeed = vfr.groundspeed * 3.6;
telemetry_vspeed = vfr.climb;
telemetry_altitude = vfr.alt;

3.7 MAVLINK_MSG_ID_GLOBAL_POSITION_INT

MAVLink传递结构体：

#define MAVLINK_MSG_ID_GLOBAL_POSITION_INT 33typedef struct __mavlink_global_position_int_t {uint32_t time_boot_ms; /*< [ms] Timestamp (time since system boot).*/int32_t lat; /*< [degE7] Latitude, expressed*/int32_t lon; /*< [degE7] Longitude, expressed*/int32_t alt; /*< [mm] Altitude (MSL). Note that virtually all GPS modules provide both WGS84 and MSL.*/int32_t relative_alt; /*< [mm] Altitude above ground*/int16_t vx; /*< [cm/s] Ground X Speed (Latitude, positive north)*/int16_t vy; /*< [cm/s] Ground Y Speed (Longitude, positive east)*/int16_t vz; /*< [cm/s] Ground Z Speed (Altitude, positive down)*/uint16_t hdg; /*< [cdeg] Vehicle heading (yaw angle), 0.0..359.99 degrees. If unknown, set to: UINT16_MAX*/
} mavlink_global_position_int_t;

OSD全局变量：

telemetry_hdg = global_position_int.hdg / 100;

3.8 MAVLINK_MSG_ID_ATTITUDE

MAVLink传递结构体：

#define MAVLINK_MSG_ID_ATTITUDE 30typedef struct __mavlink_attitude_t {uint32_t time_boot_ms; /*< [ms] Timestamp (time since system boot).*/float roll; /*< [rad] Roll angle (-pi..+pi)*/float pitch; /*< [rad] Pitch angle (-pi..+pi)*/float yaw; /*< [rad] Yaw angle (-pi..+pi)*/float rollspeed; /*< [rad/s] Roll angular speed*/float pitchspeed; /*< [rad/s] Pitch angular speed*/float yawspeed; /*< [rad/s] Yaw angular speed*/
} mavlink_attitude_t;

OSD全局变量：

telemetry_pitch = att.pitch * (180.0 / 3.141592653589793238463);
telemetry_roll = att.roll * (180.0 / 3.141592653589793238463);
telemetry_yaw = att.yaw * (180.0 / 3.141592653589793238463);

4. 飞控配置

MAVLink协议具有可配置的属性，而默认情况下，上述报文并不一定发送。其发送完全取决于当前Ardupilot的配置情况。

在Ardupilot 4.5.6版本情况下，需要进行以下步骤的配置：

4.1 配置MAVLinkV2串口

鉴于，当前硬件上使用了飞控UART8，飞控端配置如下：

注：OpenIPC FPV摄像头默认使用了115200波特率，请根据实际情况调整。

4.2 确认MAVLink端口配置数量

从这里可以计算出，一共2个MAVLink端口，依次计算出SRn_xxx，编号n。

• UART0 //SR0_
• UART8 //SR1_

4.3 配置定时MAVLink报文

• MAVLINK_MSG_ID_RAW_IMU //SR1_RAW_SENS
• MAVLINK_MSG_ID_SYS_STATUS //SR1_EXT_STAT
• MAVLINK_MSG_ID_BATTERY_STATUS //SR1_EXTRA3
• MAVLINK_MSG_ID_RC_CHANNELS_RAW //SR1_RC_CHAN
• MAVLINK_MSG_ID_GPS_RAW_INT //SR1_EXT_STAT
• MAVLINK_MSG_ID_VFR_HUD //SR1_EXTRA2
• MAVLINK_MSG_ID_GLOBAL_POSITION_INT //SR1_POSITION
• MAVLINK_MSG_ID_ATTITUDE //SR1_EXTRA1

5. 参考资料

【1】Ardupilot & OpenIPC & 基于WFB-NG构架分析和数据链路思考
【2】OpenIPC开源FPV之工程编译
【3】OpenIPC开源FPV之工程框架
【4】OpenIPC开源FPV之重要源码包
【5】OpenIPC开源FPV之重要源码启动配置
【6】OpenIPC开源FPV之固件sysupgrade升级