Specifications / Modbus Protocol / API / Bricklets (Discontinued) / Laser Range Finder Bricklet

Modbus - Laser Range Finder Bricklet¶

This is the description of the Modbus protocol for the Laser Range Finder Bricklet. General information and technical specifications for the Laser Range Finder Bricklet are summarized in its hardware description.

API¶

A general description of the Modbus protocol structure can be found here.

Basic Functions¶

BrickletLaserRangeFinder.get_distance¶

Function ID:	1
Request:	empty payload
Response:	distance – Type: uint16, Unit: 1 cm, Range: [0 to 4000]

Returns the measured distance.

Sensor hardware version 1 (see get_sensor_hardware_version) cannot measure distance and velocity at the same time. Therefore, the distance mode has to be enabled using set_mode. Sensor hardware version 3 can measure distance and velocity at the same time. Also the laser has to be enabled, see enable_laser.

If you want to get the distance periodically, it is recommended to use the CALLBACK_DISTANCE callback and set the period with set_distance_callback_period.

BrickletLaserRangeFinder.get_velocity¶

Function ID:	2
Request:	empty payload
Response:	velocity – Type: int16, Unit: 1 cm/s, Range: [-12800 to 12700]

Returns the measured velocity.

Sensor hardware version 1 (see get_sensor_hardware_version) cannot measure distance and velocity at the same time. Therefore, the velocity mode has to be enabled using set_mode. Sensor hardware version 3 can measure distance and velocity at the same time, but the velocity measurement only produces stables results if a fixed measurement rate (see set_configuration) is configured. Also the laser has to be enabled, see enable_laser.

If you want to get the velocity periodically, it is recommended to use the CALLBACK_VELOCITY callback and set the period with set_velocity_callback_period.

BrickletLaserRangeFinder.set_mode¶

Function ID:	15
Request:	mode – Type: uint8, Range: See meanings, Default: 0
Response:	no response

Note

This function is only available if you have a LIDAR-Lite sensor with hardware version 1. Use set_configuration for hardware version 3. You can check the sensor hardware version using get_sensor_hardware_version.

The LIDAR-Lite sensor (hardware version 1) has five different modes. One mode is for distance measurements and four modes are for velocity measurements with different ranges.

The following modes are available:

0: Distance is measured with resolution 1.0 cm and range 0-4000 cm
1: Velocity is measured with resolution 0.1 m/s and range is 0-12.7 m/s
2: Velocity is measured with resolution 0.25 m/s and range is 0-31.75 m/s
3: Velocity is measured with resolution 0.5 m/s and range is 0-63.5 m/s
4: Velocity is measured with resolution 1.0 m/s and range is 0-127 m/s

The following meanings are defined for the elements of this function:

For mode:

0 = Distance
1 = Velocity Max 13ms
2 = Velocity Max 32ms
3 = Velocity Max 64ms
4 = Velocity Max 127ms

BrickletLaserRangeFinder.get_mode¶

Function ID:	16
Request:	empty payload
Response:	mode – Type: uint8, Range: See meanings, Default: 0

Returns the mode as set by set_mode.

The following meanings are defined for the elements of this function:

For mode:

0 = Distance
1 = Velocity Max 13ms
2 = Velocity Max 32ms
3 = Velocity Max 64ms
4 = Velocity Max 127ms

BrickletLaserRangeFinder.enable_laser¶

Function ID:	17
Request:	empty payload
Response:	no response

Activates the laser of the LIDAR.

We recommend that you wait 250ms after enabling the laser before the first call of get_distance to ensure stable measurements.

BrickletLaserRangeFinder.disable_laser¶

Function ID:	18
Request:	empty payload
Response:	no response

Deactivates the laser of the LIDAR.

BrickletLaserRangeFinder.is_laser_enabled¶

Function ID:	19
Request:	empty payload
Response:	laser_enabled – Type: bool

Returns true if the laser is enabled, false otherwise.

BrickletLaserRangeFinder.set_configuration¶

Function ID:	25
Request:	acquisition_count – Type: uint8, Range: [1 to 255], Default: 128 enable_quick_termination – Type: bool, Default: false threshold_value – Type: uint8, Range: [0 to 255], Default: 0 measurement_frequency – Type: uint16, Unit: 1 Hz, Range: [0, 10 to 500], Default: 0
Response:	no response

Note

This function is only available if you have a LIDAR-Lite sensor with hardware version 3. Use set_mode for hardware version 1. You can check the sensor hardware version using get_sensor_hardware_version.

The Acquisition Count defines the number of times the Laser Range Finder Bricklet will integrate acquisitions to find a correlation record peak. With a higher count, the Bricklet can measure longer distances. With a lower count, the rate increases. The allowed values are 1-255.

If you set Enable Quick Termination to true, the distance measurement will be terminated early if a high peak was already detected. This means that a higher measurement rate can be achieved and long distances can be measured at the same time. However, the chance of false-positive distance measurements increases.

Normally the distance is calculated with a detection algorithm that uses peak value, signal strength and noise. You can however also define a fixed Threshold Value. Set this to a low value if you want to measure the distance to something that has very little reflection (e.g. glass) and set it to a high value if you want to measure the distance to something with a very high reflection (e.g. mirror). Set this to 0 to use the default algorithm. The other allowed values are 1-255.

Set the Measurement Frequency to force a fixed measurement rate. If set to 0, the Laser Range Finder Bricklet will use the optimal frequency according to the other configurations and the actual measured distance. Since the rate is not fixed in this case, the velocity measurement is not stable. For a stable velocity measurement you should set a fixed measurement frequency. The lower the frequency, the higher is the resolution of the calculated velocity. The allowed values are 10Hz-500Hz (and 0 to turn the fixed frequency off).

New in version 2.0.3 (Plugin).

BrickletLaserRangeFinder.get_configuration¶

Function ID:	26
Request:	empty payload
Response:	acquisition_count – Type: uint8, Range: [1 to 255], Default: 128 enable_quick_termination – Type: bool, Default: false threshold_value – Type: uint8, Range: [0 to 255], Default: 0 measurement_frequency – Type: uint16, Unit: 1 Hz, Range: [0, 10 to 500], Default: 0

Returns the configuration as set by set_configuration.

New in version 2.0.3 (Plugin).

Advanced Functions¶

BrickletLaserRangeFinder.set_moving_average¶

Function ID:	13
Request:	distance_average_length – Type: uint8, Range: [0 to 30], Default: 10 velocity_average_length – Type: uint8, Range: [0 to 30], Default: 10
Response:	no response

Sets the length of a moving averaging for the distance and velocity.

Setting the length to 0 will turn the averaging completely off. With less averaging, there is more noise on the data.

BrickletLaserRangeFinder.get_moving_average¶

Function ID:	14
Request:	empty payload
Response:	distance_average_length – Type: uint8, Range: [0 to 30], Default: 10 velocity_average_length – Type: uint8, Range: [0 to 30], Default: 10

Returns the length moving average as set by set_moving_average.

BrickletLaserRangeFinder.get_sensor_hardware_version¶

Function ID:	24
Request:	empty payload
Response:	version – Type: uint8, Range: See meanings

Returns the LIDAR-Lite hardware version.

New in version 2.0.3 (Plugin).

The following meanings are defined for the elements of this function:

For version:

1 = 1
3 = 3

BrickletLaserRangeFinder.get_identity¶

Function ID:	255
Request:	empty payload
Response:	uid – Type: char[8] connected_uid – Type: char[8] position – Type: char, Range: ['a' to 'h', 'z'] hardware_version – Type: uint8[3] 0: major – Type: uint8, Range: [0 to 255] 1: minor – Type: uint8, Range: [0 to 255] 2: revision – Type: uint8, Range: [0 to 255] firmware_version – Type: uint8[3] 0: major – Type: uint8, Range: [0 to 255] 1: minor – Type: uint8, Range: [0 to 255] 2: revision – Type: uint8, Range: [0 to 255] device_identifier – Type: uint16, Range: [0 to 2¹⁶ - 1]

Returns the UID, the UID where the Bricklet is connected to, the position, the hardware and firmware version as well as the device identifier.

The position can be 'a', 'b', 'c', 'd', 'e', 'f', 'g' or 'h' (Bricklet Port). A Bricklet connected to an Isolator Bricklet is always at position 'z'.

The device identifier numbers can be found here.

Callback Configuration Functions¶

BrickletLaserRangeFinder.set_distance_callback_period¶

Function ID:	3
Request:	period – Type: uint32, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0
Response:	no response

Sets the period with which the CALLBACK_DISTANCE callback is triggered periodically. A value of 0 turns the callback off.

The CALLBACK_DISTANCE callback is only triggered if the distance value has changed since the last triggering.

BrickletLaserRangeFinder.get_distance_callback_period¶

Function ID:	4
Request:	empty payload
Response:	period – Type: uint32, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0

Returns the period as set by set_distance_callback_period.

BrickletLaserRangeFinder.set_velocity_callback_period¶

Function ID:	5
Request:	period – Type: uint32, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0
Response:	no response

Sets the period with which the CALLBACK_VELOCITY callback is triggered periodically. A value of 0 turns the callback off.

The CALLBACK_VELOCITY callback is only triggered if the velocity value has changed since the last triggering.

BrickletLaserRangeFinder.get_velocity_callback_period¶

Function ID:	6
Request:	empty payload
Response:	period – Type: uint32, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0

Returns the period as set by set_velocity_callback_period.

BrickletLaserRangeFinder.set_distance_callback_threshold¶

Function ID:	7
Request:	option – Type: char, Range: See meanings, Default: 'x' min – Type: uint16, Unit: 1 cm, Range: [0 to 2¹⁶ - 1], Default: 0 max – Type: uint16, Unit: 1 cm, Range: [0 to 2¹⁶ - 1], Default: 0
Response:	no response

Sets the thresholds for the CALLBACK_DISTANCE_REACHED callback.

The following options are possible:

Option	Description
'x'	Callback is turned off
'o'	Callback is triggered when the distance value is outside the min and max values
'i'	Callback is triggered when the distance value is inside the min and max values
'<'	Callback is triggered when the distance value is smaller than the min value (max is ignored)
'>'	Callback is triggered when the distance value is greater than the min value (max is ignored)

The following meanings are defined for the elements of this function:

For option:

'x' = Off
'o' = Outside
'i' = Inside
'<' = Smaller
'>' = Greater

BrickletLaserRangeFinder.get_distance_callback_threshold¶

Function ID:	8
Request:	empty payload
Response:	option – Type: char, Range: See meanings, Default: 'x' min – Type: uint16, Unit: 1 cm, Range: [0 to 2¹⁶ - 1], Default: 0 max – Type: uint16, Unit: 1 cm, Range: [0 to 2¹⁶ - 1], Default: 0

Returns the threshold as set by set_distance_callback_threshold.

The following meanings are defined for the elements of this function:

For option:

'x' = Off
'o' = Outside
'i' = Inside
'<' = Smaller
'>' = Greater

BrickletLaserRangeFinder.set_velocity_callback_threshold¶

Function ID:	9
Request:	option – Type: char, Range: See meanings, Default: 'x' min – Type: int16, Unit: 1 cm/s, Range: [-2¹⁵ to 2¹⁵ - 1], Default: 0 max – Type: int16, Unit: 1 cm/s, Range: [-2¹⁵ to 2¹⁵ - 1], Default: 0
Response:	no response

Sets the thresholds for the CALLBACK_VELOCITY_REACHED callback.

The following options are possible:

Option	Description
'x'	Callback is turned off
'o'	Callback is triggered when the velocity is outside the min and max values
'i'	Callback is triggered when the velocity is inside the min and max values
'<'	Callback is triggered when the velocity is smaller than the min value (max is ignored)
'>'	Callback is triggered when the velocity is greater than the min value (max is ignored)

The following meanings are defined for the elements of this function:

For option:

'x' = Off
'o' = Outside
'i' = Inside
'<' = Smaller
'>' = Greater

BrickletLaserRangeFinder.get_velocity_callback_threshold¶

Function ID:	10
Request:	empty payload
Response:	option – Type: char, Range: See meanings, Default: 'x' min – Type: int16, Unit: 1 cm/s, Range: [-2¹⁵ to 2¹⁵ - 1], Default: 0 max – Type: int16, Unit: 1 cm/s, Range: [-2¹⁵ to 2¹⁵ - 1], Default: 0

Returns the threshold as set by set_velocity_callback_threshold.

The following meanings are defined for the elements of this function:

For option:

'x' = Off
'o' = Outside
'i' = Inside
'<' = Smaller
'>' = Greater

BrickletLaserRangeFinder.set_debounce_period¶

Function ID:	11
Request:	debounce – Type: uint32, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 100
Response:	no response

Sets the period with which the threshold callbacks

CALLBACK_DISTANCE_REACHED,
CALLBACK_VELOCITY_REACHED,

are triggered, if the thresholds

set_distance_callback_threshold,
set_velocity_callback_threshold,

keep being reached.

BrickletLaserRangeFinder.get_debounce_period¶

Function ID:	12
Request:	empty payload
Response:	debounce – Type: uint32, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 100

Returns the debounce period as set by set_debounce_period.

Callbacks¶

BrickletLaserRangeFinder.CALLBACK_DISTANCE¶

Function ID:	20
Response:	distance – Type: uint16, Unit: 1 cm, Range: [0 to 4000]

This callback is triggered periodically with the period that is set by set_distance_callback_period. The response value is the distance value of the sensor.

The CALLBACK_DISTANCE callback is only triggered if the distance value has changed since the last triggering.

BrickletLaserRangeFinder.CALLBACK_VELOCITY¶

Function ID:	21
Response:	velocity – Type: int16, Unit: 1 cm/s, Range: [-12800 to 12700]

This callback is triggered periodically with the period that is set by set_velocity_callback_period. The response value is the velocity value of the sensor.

The CALLBACK_VELOCITY callback is only triggered if the velocity has changed since the last triggering.

BrickletLaserRangeFinder.CALLBACK_DISTANCE_REACHED¶

Function ID:	22
Response:	distance – Type: uint16, Unit: 1 cm, Range: [0 to 4000]

This callback is triggered when the threshold as set by set_distance_callback_threshold is reached. The response value is the distance value of the sensor.

If the threshold keeps being reached, the callback is triggered periodically with the period as set by set_debounce_period.

BrickletLaserRangeFinder.CALLBACK_VELOCITY_REACHED¶

Function ID:	23
Response:	velocity – Type: int16, Unit: 1 cm/s, Range: [-12800 to 12700]

This callback is triggered when the threshold as set by set_velocity_callback_threshold is reached. The response value is the velocity value of the sensor.

If the threshold keeps being reached, the callback is triggered periodically with the period as set by set_debounce_period.