Frame Reference

Each frame emitted by the unit is decoded into a struct carried by a variant of OscpFrame.

`OscpFrame` variant	Header value	Struct	Length constant	Length
`OscpFrame::Raw`	`0x00`	`OscpRaw`	`OSCP_RAW_LEN`	61 B
`OscpFrame::Euler`	`0x01`	`OscpEuler`	`OSCP_EULER_LEN`	25 B
`OscpFrame::Quat`	`0x02`	`OscpQuat`	`OSCP_QUAT_LEN`	29 B
`OscpFrame::RotMat`	`0x03`	`OscpRotMat`	`OSCP_ROT_MAT_LEN`	49 B
`OscpFrame::Gnss`	`0x04`	`OscpGnss`	`OSCP_GNSS_LEN`	64 B
`OscpFrame::Debug1`	`0x05`	`OscpDebug1`	`OSCP_DEBUG_1_LEN`	58 B
`OscpFrame::Debug2`	`0x06`	`OscpDebug2`	`OSCP_DEBUG_2_LEN`	58 B
`OscpFrame::Startup`	`0x07`	`OscpStartup`	`OSCP_STARTUP_LEN`	40 B

Command responses

Command responses are reported as OscpFrame::CmdResponse(OscpFrameCmd) with one of OscpFrameCmd::Success (0xA0), ::Failed (0xA1), ::Unknown (0xA2) or ::NotImpl (0xA3). These values are defined by the library, not by the IMU protocol. Only the RS422 parser produces this variant; see Command classes.

The header byte

The first byte of every operating frame is stored in header_byte as an OscpHeader. Its fields are read with the following methods:

let t  = e.header_byte.frame_type();         /* bits [2:0] -> Result<OscpFrameType, u8> */
let om = e.header_byte.operating_mode();     /* bits [5:3] -> Result<OscpOperatingMode, u8> */
let mc = e.header_byte.misalignment_corr();  /* bits [7:6] -> Result<OscpMisalignmentCorr, u8> */

Field	Bits	Values
Frame type	`[2:0]`	See table above (`OscpFrameType::Raw` … `::Startup`)
Operating mode	`[5:3]`	`OscpOperatingMode::Idle` / `::Low` / `::Medium`
Misalignment correction	`[7:6]`	`OscpMisalignmentCorr::Disabled` / `::Enabled`

A method returns Err(value) if the bits do not map to a variant. The raw byte is returned by header_byte.to_byte().

The status byte

Every frame contains a status byte. 0x00 indicates no fault. Other values are a combination of the following masks:

Mask	Value	Meaning
`OSCP_STATUS_OK`	`0x00`	No fault
`OSCP_STATUS_OVERRUN`	`0x01`	IMU real-time controller overrun
`OSCP_STATUS_MEMS_ERR`	`0x02`	MEMS sensor error
`OSCP_STATUS_INCL_ERR`	`0x04`	Inclinometer error
`OSCP_STATUS_MAG_ERR`	`0x08`	Magnetometer error
`OSCP_STATUS_TEMP_ERR`	`0x10`	Temperature sensor error
`OSCP_STATUS_GNSS_ERR`	`0x20`	GNSS error (G variants only)
`OSCP_STATUS_OG_ERR`	`0x40`	Optical gyroscope error (optical-based models only)

if e.status & OSCP_STATUS_MEMS_ERR != 0 { /* handle MEMS fault */ }

Raw frame - `OscpRaw`

Raw sensor output.

Fields

Field	Type	Unit
`header_byte`	`OscpHeader`	-
`counter`	`u8`	-
`timestamp_ms`	`u64`	ms
`gyro_x/y/z`	`f32`	dps
`accel_x/y/z`	`f32`	g
`incl_x/y`	`f32`	mg
`mag_x/y/z`	`f32`	µT
`temp`	`f32`	°C
`status`	`u8`	-
`crc`	`u16`	-

Euler frame - `OscpEuler`

AHRS attitude as Euler angles.

Fields

Field	Type	Unit
`header_byte`	`OscpHeader`	-
`counter`	`u8`	-
`timestamp_ms`	`u64`	ms
`roll`	`f32`	deg
`pitch`	`f32`	deg
`yaw`	`f32`	deg
`status`	`u8`	-
`crc`	`u16`	-

Quaternion frame - `OscpQuat`

AHRS attitude as a unit quaternion (w, x, y, z).

Fields

Field	Type	Unit
`header_byte`	`OscpHeader`	-
`counter`	`u8`	-
`timestamp_ms`	`u64`	ms
`w`, `x`, `y`, `z`	`f32`	- (normalized)
`status`	`u8`	-
`crc`	`u16`	-

Rotation matrix frame - `OscpRotMat`

AHRS attitude as a 3×3 direction-cosine matrix.

Fields

Field	Type	Notes
`header_byte`	`OscpHeader`	-
`counter`	`u8`	-
`timestamp_ms`	`u64`	ms
`rm`	`[[f32; 3]; 3]`	Row-major direction-cosine matrix
`status`	`u8`	-
`crc`	`u16`	-

GNSS frame - `OscpGnss`

Position, velocity and fix quality.

Fields

Field	Type	Unit
`header_byte`	`OscpHeader`	-
`counter`	`u8`	-
`timestamp_ms`	`u64`	ms
`gnss_fix_type`	`u8`	-
`num_satellites`	`u8`	count
`longitude`	`f32`	deg
`latitude`	`f32`	deg
`height`	`i32`	mm
`horizontal_accuracy`	`u32`	mm
`vertical_accuracy`	`u32`	mm
`velocity_north/east/down`	`i32`	mm/s
`speed_accuracy`	`u32`	mm/s
`heading_of_motion`	`f32`	deg
`heading_accuracy`	`f32`	deg
`pdop`	`f32`	-
`gnss_flags`	`GnssFlags`	See below
`status`	`u8`	-
`crc`	`u16`	-

GnssFlags methods:

Method	Bits	Returns
`gnss_fix_ok()`	`[0]`	`bool`, fix valid
`invalid_llh()`	`[1]`	`bool`, latitude/longitude/height invalid
`last_correction_age()`	`[7:4]`	`u8`

Debug frames - `OscpDebug1` / `OscpDebug2`

Diagnostic frames. Debug 1 contains the per-axis sensor bias user registers and the user filter settings. Debug 2 contains the user magnetometer calibration matrix and the AHRS fusion parameters. Register values are raw u32; refer to the datasheet for their interpretation. Both frames are sent in response to OFD (oscp_cmd_of(..., OscpFrameSel::Debug, ...)) in CONFIG state.

Packed configuration bytes

Field	Type	Methods
`gyro_filter_cfg` / `accel_filter_cfg` (Debug 1)	`FilterCfg`	`filters()` `[1:0]`, `lpf()` `[4:2]`, `hpf()` `[7:5]`
`fusion_cfg` (Debug 2)	`FusionCfg`	`fusion_convention()` `[3:0]`, `fusion_heading_source()` `[7:4]`

Debug frames contain counter but not timestamp_ms.

Startup frame - `OscpStartup`

Sent once at boot, and in response to SUF (oscp_cmd_suf(...)) in CONFIG state. Contains the unit identification and saved configuration.

Fields

Field	Type	Notes
`header_byte`	`OscpHeader`	-
`mark_number`	`[u8; 10]`	Byte array; see note below
`unit_number`	`u16`	Unit number
`sw_major_ver` / `sw_minor_ver` / `sw_patch_ver`	`u8`	Firmware version
`enabled_frames`	`u8`	Bitmask, see below
`dyn_range_cfg`	`DynRangeCfg`	`gyro_dr()` `[3:0]`, `accel_dr()` `[7:4]`
`gyro_filter_cfg` / `accel_filter_cfg`	`FilterCfg`	`filters()`, `lpf()`, `hpf()`
`incl_ahrs_cfg`	`InclAhrsCfg`	`incl_dr()` `[3:0]`, `ahrs_convention()` `[5:4]`, `ahrs_heading_src()` `[7:6]`
`ahrs_gain` / `ahrs_accel_rej` / `ahrs_mag_rej`	`f32`	AHRS configuration
`ahrs_rec_trig_per`	`u32`	AHRS recovery trigger period (s)
`status`	`u8`	-
`crc`	`u16`	-

enabled_frames masks:

Mask	Value
`OSCP_ENABLE_RAW`	`0x01`
`OSCP_ENABLE_EULER`	`0x02`
`OSCP_ENABLE_QUAT`	`0x04`
`OSCP_ENABLE_ROT_MAT`	`0x08`
`OSCP_ENABLE_GNSS`	`0x10`

Reading back dynamic ranges

gyro_dr(), accel_dr() and incl_dr() return the 4-bit code reported by the unit. This code is not the value written by DRG, DRA or DRI and is not sequential. Convert it with from_dyn_range_code:

use oscp_imu::{OscpGyroDr, OscpAccelDr, OscpInclDr};

let gyro  = OscpGyroDr::from_dyn_range_code(s.dyn_range_cfg.gyro_dr());   /* e.g. Ok(OscpGyroDr::Dps250) */
let accel = OscpAccelDr::from_dyn_range_code(s.dyn_range_cfg.accel_dr());
let incl  = OscpInclDr::from_dyn_range_code(s.incl_ahrs_cfg.incl_dr());

Readback code mapping

Code	Gyroscope	Accelerometer	Inclinometer
`0b0000`	±250 °/s	±2 g	±0.5 g
`0b0001`	±4000 °/s	±16 g	±3.0 g
`0b0010`	±125 °/s	±4 g	±1.0 g
`0b0011`	-	±8 g	±2.0 g
`0b0100`	±500 °/s	-	-
`0b1000`	±1000 °/s	-	-
`0b1100`	±2000 °/s	-	-

Unlisted codes return Err(code).

mark_number is a byte array

mark_number is 10 bytes with no terminator. UTF-8 validity is not guaranteed. Convert before printing and remove trailing padding:

let mark = core::str::from_utf8(&s.mark_number)
    .unwrap_or("<invalid>")
    .trim_end_matches('\0');

Struct layout

Frame structs are not packed. Each field is decoded with from_le_bytes into a naturally aligned struct, so field access has no alignment restrictions. All frame types implement Copy.

Next: Command reference →

Frame Reference

The header byte

The status byte

Raw frame - OscpRaw

Euler frame - OscpEuler

Quaternion frame - OscpQuat

Rotation matrix frame - OscpRotMat

GNSS frame - OscpGnss

Debug frames - OscpDebug1 / OscpDebug2

Startup frame - OscpStartup

Reading back dynamic ranges

Raw frame - `OscpRaw`

Euler frame - `OscpEuler`

Quaternion frame - `OscpQuat`

Rotation matrix frame - `OscpRotMat`

GNSS frame - `OscpGnss`

Debug frames - `OscpDebug1` / `OscpDebug2`

Startup frame - `OscpStartup`