Data Structures
struct	vmu_tx
	Data streamed for Heading. More...

struct	vmu_txyz
	Data streamed for Accelerometers, Gyroscopes, Magnetometers and Euler angles. More...

struct	vmu_twxyz
	Data streamed for Quaternions. More...

struct	vmu_text
	Textual data returned by device and library. More...

struct	vmu_status
	Device status - enabled sensors, resolution, rate and streamed data. More...

struct	vmu_size
	Array sizes for `vmu_data` arrays. More...

struct	vmu_data
	Structure with multiple types of data returned from the device. More...

struct	vmu
	Internal library data passed around by the user. More...

Enumerations
enum	{ VMU_MAX_STRING_SIZE =255 }

enum	vmu_sensors_enum { VMU_SENSORS_ACCEL =0x01, VMU_SENSORS_GYRO =0x02, VMU_SENSORS_MAG =0x04 }
	Constants used for determining enabled sensors. More...

enum	vmu_resolution_enum { VMU_RESOLUTION_ACCEL_2G =0x01, VMU_RESOLUTION_ACCEL_4G =0x02, VMU_RESOLUTION_ACCEL_8G =0x04, VMU_RESOLUTION_ACCEL_16G =0x08, VMU_RESOLUTION_GYRO_250DPS =0x10, VMU_RESOLUTION_GYRO_500DPS =0x20, VMU_RESOLUTION_GYRO_1000DPS =0x40, VMU_RESOLUTION_GYRO_2000DPS =0x80 }
	Constants used for determining and setting sensor resolution. More...

enum	vmu_stream_enum { VMU_STREAM_ACCEL =0x01, VMU_STREAM_GYRO = 0x02, VMU_STREAM_QUAT =0x04, VMU_STREAM_MAG =0x08, VMU_STREAM_EULER =0x10, VMU_STREAM_HEAD =0x40 }
	Constants used for setting and determining streamed data. More...

enum	vmu_retval_enum { VMU_ERROR =-1, VMU_OK =0, VMU_DATA_PENDING =1 }
	Constants returned by most of library functions. More...

Functions
int	vmu_read_all (struct vmu v, struct vmu_data data)
	Read multiple types of data simultanously. More...

int	vmu_stream (struct vmu *v, uint32_t stream)
	Make the device stream particular data types. More...

int	vmu_resolution (struct vmu *v, uint32_t resolution)
	Set accelerometer and/or gyroscope resolutions. More...

int	vmu_selftest (struct vmu v, struct vmu_text data)
	Command device to perform selftest. More...

int	vmu_calibrate (struct vmu v, struct vmu_text data)
	Command device to perform calibration. More...

int	vmu_status (struct vmu v, struct vmu_status data)
	Retrieve device status. More...

int	vmu_fd (struct vmu *v)
	Get file descriptor used for serial communication with the device. More...

Init and teardown
struct vmu *	vmu_init (const char *tty)
	initialize internal library data. More...

int	vmu_close (struct vmu *v)
	free library resources More...

Convinient read

Simplified read functions for single type of data (e.g. only euler). If you need to read multiple types of data use vmu_read_all instead.

Functions will block waiting for data unless last call returned value > size. Timeout with return value VMU_ERROR and errno EAGAIN indicates device is not sending data type for some reason.

Other data types are discarded silently without parsing.

Perfomance hints:

use vmu_stream so that device streams only data you need

Parameters

v	pointer to internal library data
data	user supplied array
size	user supplied array size

Returns

value > size indicates user array was filled and more data is pending (without blocking)
value <= size indicates number of data points returned in array (next call will block)
VMU_ERROR indicates error, query errno for the details

See Also: vmu_stream, vmu_read_all

Example:

int status, i;
struct vmu_txyz euler[10];
while( (status=vmu_euler(v, euler, 10)) != VMU_ERROR  )
{
   for(i=0; i<status && i<10; ++i)
      printf("[%lu ms] x=%f y=%f z=%f\n", euler[i].timeout_ms, euler[i].x, euler[i].y, euler[i].z);
}

int vmu_accel (struct vmu *v, struct vmu_txyz *data, int size)

Read only accelerometer data.

int vmu_gyro (struct vmu *v, struct vmu_txyz *data, int size)

Read only gyroscope data data.

int vmu_mag (struct vmu *v, struct vmu_txyz *data, int size)

Read only magnetometer data.

int vmu_euler (struct vmu *v, struct vmu_txyz *data, int size)

Read only euler data.

int vmu_quat (struct vmu *v, struct vmu_twxyz *data, int size)

Read only quaternion data.

int vmu_head (struct vmu *v, struct vmu_tx *data, int size)

Read only heading data.

Detailed Description

Enumeration Type Documentation

enum vmu_resolution_enum

Constants used for determining and setting sensor resolution.

See Also: vmu_status, vmu_resolution

enum vmu_retval_enum

Constants returned by most of library functions.

Enumerator
VMU_ERROR	error occured with errno set
VMU_OK	succesfull execution
VMU_DATA_PENDING	succesfull execution and more data pending without blocking

enum vmu_sensors_enum

Constants used for determining enabled sensors.

See Also: vmu_status

enum vmu_stream_enum

Constants used for setting and determining streamed data.

See Also: vmu_stream, vmu_status

Function Documentation

int vmu_calibrate	(	struct vmu *	v,
		struct vmu_text *	data
	)

Command device to perform calibration.

Blocks for around 4 seconds while device performs calibration. All textual data output by the device is concatenated in data argument. All non-textual data is discarded during the process. The device needs to remain still on a flat surface with its Z-axis pointing upward during the process. You don't have to repeat this procedure every time you power on the sensor.

Note - there is undocummented (VMU User Guide 1.3) magnetometer calibration procedure. Magnetometer calibration is essential to reduce drift on Z (heading) axis. While powering up the sensor move it around in multiple orientations. Do it until the Euler angles indicates 0 degrees while the sensor has its Y axis pointing North. As of firmware 1.01 this has to be repeated every time you power on the sensor.

Parameters

v	pointer to internal library data
data	argument filled with textual data

Returns

VMU_OK if calibration succeded, query data for the details
VMU_ERROR on IO error, calibration failure or timeout, query data and errno for the details

int vmu_close ( struct vmu * v )

free library resources

Frees memory and restores terminal settings.

May be safely called with NULL argument.

Parameters

v	pointer to internal library data

Returns

VMU_OK on success
VMU_ERROR on error, query errno for the details

Example:

vmu_close(v);

int vmu_fd ( struct vmu * v )

Get file descriptor used for serial communication with the device.

Library user should not directly read or write from or to descriptor. This function is intended to be used in synchronous I/O multiplexing (select, poll).

Parameters

v	pointer to internal library data

Returns: file descriptor

struct vmu* vmu_init ( const char * tty )

initialize internal library data.

Parameters

tty	device like "/dev/ttyACM0"

Returns

pointer to internal library data
NULL on error with errno set

See Also: vmu_close

Example:

struct vmu *v=vmu_init("/dev/ttyACM0");

int vmu_read_all	(	struct vmu *	v,
		struct vmu_data *	data
	)

Read multiple types of data simultanously.

Use this function if you need to read multiple types of data (e.g. euler and magnetometer).

If you care only about single data type use one of convinience functions instead.

Function will block waiting for data unless last call returned VMU_DATA_PENDING. Timeout with return value VMU_ERROR and errno EAGAIN indicates device is not sending data types for some reason.

Data types with 0 size in data parameter are discarded silently without parsing.

Perfomance hints:

use vmu_stream so that device streams only data you need

Parameters

v	pointer to internal library data
data	user supplied arrays with sizes

Returns

VMU_OK indicates user arrays in data parameter were filled
VMU_DATA_PENDING indicates at least one array in data parameter was filled completely and more data is pending (without blocking)
VMU_ERROR indicates error, query errno for the details

See Also: vmu_stream, vmu_accel, vmu_gyro, vmu_mag, vmu_euler, vmu_quat, vmu_head

int vmu_resolution	(	struct vmu *	v,
		uint32_t	resolution
	)

Set accelerometer and/or gyroscope resolutions.

Blocks until resolution is set, error or timeout occurs.

Streaming Heading, Euler or Quaternion data forces:

2000 dps for gyroscope
2g for accelerometer

It setting resolution only for accelerometer or gyroscope the second remains unchanged.

errno values:

EINVAL if resolution argument is not sane
ENOTSUP if requested incompatible resolution while streaming Heading, Euler or Quaternion data
EAGAIN if timeout occured during communication with the device
other IO specific errno values are possible

Parameters

v	pointer to internal library data
resolution	logical combination of vmu_resolution_enum values

Returns

VMU_OK if setting resolution succeded
VMU_ERROR on IO error or invalid resolution argument, query errno for the details

See Also: vmu_resolution_enum

Example:

vmu_resolution(v, VMU_RESOLUTION_ACCEL_16G | VMU_RESOLUTION_GYRO_1000DPS);

int vmu_selftest	(	struct vmu *	v,
		struct vmu_text *	data
	)

Command device to perform selftest.

Blocks for around 2 seconds while device performs selftest. All textual data output by the device is concatenated in data argument. All non-textual data is discarded during the process.

The device needs to remain still on a flat surface with its Z-axis pointing upward during the process.

Parameters

v	pointer to internal library data
data	argument filled with textual data

Returns

VMU_OK if selftest succeded, query data for the details
VMU_ERROR on IO error, selftest failure or timeout, query data and errno for the details

int vmu_status	(	struct vmu *	v,
		struct vmu_status *	data
	)

Retrieve device status.

Blocks until device returns status, error or timeout occurs.

Non status data types are discarded while waiting for device status.

Parameters

v	pointer to internal library data
data	argument filled with status data

Returns

VMU_OK on success
VMU_ERROR on failure, query errno for the details

int vmu_stream	(	struct vmu *	v,
		uint32_t	stream
	)

Make the device stream particular data types.

Function blocks until one of:

new streaming parameters are set
error occurs (including timeout with errno EAGAIN)

Parameters

v	pointer to internal library data
stream	logical sum of values from vmu_stream_enum

Returns

VMU_OK indicates device will stream requested data types
VMU_ERROR indicates error, query errno for the details

See Also: vmu_stream_enum

Example:

vmu_stream(v, VMU_STREAM_EULER | VMU_STREAM_MAG);

Data Structures

Enumerations

Functions

Init and teardown

Convinient read

Detailed Description

Enumeration Type Documentation

Function Documentation