Modbus - Laser Range Finder Bricklet 2.0

This is the description of the Modbus protocol for the Laser Range Finder Bricklet 2.0. General information and technical specifications for the Laser Range Finder Bricklet 2.0 are summarized in its hardware description.

API

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

Basic Functions

BrickletLaserRangeFinderV2.get_distance
Function ID:

1

Request:

empty payload

Response:
  • distance -- int16

Returns the measured distance. The value has a range of 0 to 4000 and is given in cm.

The laser has to be enabled, see set_enable.

If you want to get the value periodically, it is recommended to use the CALLBACK_DISTANCE callback. You can set the callback configuration with set_distance_callback_configuration.

BrickletLaserRangeFinderV2.get_velocity
Function ID:

5

Request:

empty payload

Response:
  • velocity -- int16

Returns the measured velocity. The value has a range of -12800 to 12700 and is given in 1/100 m/s.

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 set_enable.

If you want to get the value periodically, it is recommended to use the CALLBACK_VELOCITY callback. You can set the callback configuration with set_velocity_callback_configuration.

BrickletLaserRangeFinderV2.set_enable
Function ID:

9

Request:
  • enable -- bool
Response:

no response

Enables the laser of the LIDAR if set to true.

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

BrickletLaserRangeFinderV2.get_enable
Function ID:

10

Request:

empty payload

Response:
  • enable -- bool

Returns the value as set by set_enable.

BrickletLaserRangeFinderV2.set_configuration
Function ID:

11

Request:
  • acquisition_count -- uint8
  • enable_quick_termination -- bool
  • threshold_value -- uint8
  • measurement_frequency -- uint16
Response:

no response

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 in Hz 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).

The default values for Acquisition Count, Enable Quick Termination, Threshold Value and Measurement Frequency are 128, false, 0 and 0.

BrickletLaserRangeFinderV2.get_configuration
Function ID:

12

Request:

empty payload

Response:
  • acquisition_count -- uint8
  • enable_quick_termination -- bool
  • threshold_value -- uint8
  • measurement_frequency -- uint16

Returns the configuration as set by set_configuration.

BrickletLaserRangeFinderV2.set_distance_led_config
Function ID:

17

Request:
  • config -- uint8
Response:

no response

Configures the distance LED to be either turned off, turned on, blink in heartbeat mode or show the distance (brighter = object is nearer).

The default value is 3 (show distance).

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

  • 0: off, for config
  • 1: on, for config
  • 2: show heartbeat, for config
  • 3: show distance, for config
BrickletLaserRangeFinderV2.get_distance_led_config
Function ID:

18

Request:

empty payload

Response:
  • config -- uint8

Returns the LED configuration as set by set_distance_led_config

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

  • 0: off, for config
  • 1: on, for config
  • 2: show heartbeat, for config
  • 3: show distance, for config

Advanced Functions

BrickletLaserRangeFinderV2.set_moving_average
Function ID:

13

Request:
  • distance_average_length -- uint8
  • velocity_average_length -- uint8
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.

The range for the averaging is 0-255.

The default value is 10.

BrickletLaserRangeFinderV2.get_moving_average
Function ID:

14

Request:

empty payload

Response:
  • distance_average_length -- uint8
  • velocity_average_length -- uint8

Returns the length moving average as set by set_moving_average.

BrickletLaserRangeFinderV2.set_offset_calibration
Function ID:

15

Request:
  • offset -- int16
Response:

no response

The offset is given in cm and added to the measured distance. It is saved in non-volatile memory, you only have to set it once.

The Bricklet comes with a per-sensor factory-calibrated offset value, you should not have to call this function.

If you want to re-calibrate the offset you first have to set it to 0. Calculate the offset by measuring the distance to a known distance and set it again.

BrickletLaserRangeFinderV2.get_offset_calibration
Function ID:

16

Request:

empty payload

Response:
  • offset -- int16

Returns the offset value as set by set_offset_calibration.

BrickletLaserRangeFinderV2.get_spitfp_error_count
Function ID:

234

Request:

empty payload

Response:
  • error_count_ack_checksum -- uint32
  • error_count_message_checksum -- uint32
  • error_count_frame -- uint32
  • error_count_overflow -- uint32

Returns the error count for the communication between Brick and Bricklet.

The errors are divided into

  • ACK checksum errors,
  • message checksum errors,
  • framing errors and
  • overflow errors.

The errors counts are for errors that occur on the Bricklet side. All Bricks have a similar function that returns the errors on the Brick side.

BrickletLaserRangeFinderV2.set_bootloader_mode
Function ID:

235

Request:
  • mode -- uint8
Response:
  • status -- uint8

Sets the bootloader mode and returns the status after the requested mode change was instigated.

You can change from bootloader mode to firmware mode and vice versa. A change from bootloader mode to firmware mode will only take place if the entry function, device identifier and CRC are present and correct.

This function is used by Brick Viewer during flashing. It should not be necessary to call it in a normal user program.

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

  • 0: bootloader, for mode
  • 1: firmware, for mode
  • 2: bootloader wait for reboot, for mode
  • 3: firmware wait for reboot, for mode
  • 4: firmware wait for erase and reboot, for mode
  • 0: ok, for status
  • 1: invalid mode, for status
  • 2: no change, for status
  • 3: entry function not present, for status
  • 4: device identifier incorrect, for status
  • 5: crc mismatch, for status
BrickletLaserRangeFinderV2.get_bootloader_mode
Function ID:

236

Request:

empty payload

Response:
  • mode -- uint8

Returns the current bootloader mode, see set_bootloader_mode.

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

  • 0: bootloader, for mode
  • 1: firmware, for mode
  • 2: bootloader wait for reboot, for mode
  • 3: firmware wait for reboot, for mode
  • 4: firmware wait for erase and reboot, for mode
BrickletLaserRangeFinderV2.set_write_firmware_pointer
Function ID:

237

Request:
  • pointer -- uint32
Response:

no response

Sets the firmware pointer for write_firmware. The pointer has to be increased by chunks of size 64. The data is written to flash every 4 chunks (which equals to one page of size 256).

This function is used by Brick Viewer during flashing. It should not be necessary to call it in a normal user program.

BrickletLaserRangeFinderV2.write_firmware
Function ID:

238

Request:
  • data -- uint8[64]
Response:
  • status -- uint8

Writes 64 Bytes of firmware at the position as written by set_write_firmware_pointer before. The firmware is written to flash every 4 chunks.

You can only write firmware in bootloader mode.

This function is used by Brick Viewer during flashing. It should not be necessary to call it in a normal user program.

BrickletLaserRangeFinderV2.set_status_led_config
Function ID:

239

Request:
  • config -- uint8
Response:

no response

Sets the status LED configuration. By default the LED shows communication traffic between Brick and Bricklet, it flickers once for every 10 received data packets.

You can also turn the LED permanently on/off or show a heartbeat.

If the Bricklet is in bootloader mode, the LED is will show heartbeat by default.

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

  • 0: off, for config
  • 1: on, for config
  • 2: show heartbeat, for config
  • 3: show status, for config
BrickletLaserRangeFinderV2.get_status_led_config
Function ID:

240

Request:

empty payload

Response:
  • config -- uint8

Returns the configuration as set by set_status_led_config

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

  • 0: off, for config
  • 1: on, for config
  • 2: show heartbeat, for config
  • 3: show status, for config
BrickletLaserRangeFinderV2.get_chip_temperature
Function ID:

242

Request:

empty payload

Response:
  • temperature -- int16

Returns the temperature in °C as measured inside the microcontroller. The value returned is not the ambient temperature!

The temperature is only proportional to the real temperature and it has bad accuracy. Practically it is only useful as an indicator for temperature changes.

BrickletLaserRangeFinderV2.reset
Function ID:243
Request:empty payload
Response:no response

Calling this function will reset the Bricklet. All configurations will be lost.

After a reset you have to create new device objects, calling functions on the existing ones will result in undefined behavior!

BrickletLaserRangeFinderV2.write_uid
Function ID:

248

Request:
  • uid -- uint32
Response:

no response

Writes a new UID into flash. If you want to set a new UID you have to decode the Base58 encoded UID string into an integer first.

We recommend that you use Brick Viewer to change the UID.

BrickletLaserRangeFinderV2.read_uid
Function ID:

249

Request:

empty payload

Response:
  • uid -- uint32

Returns the current UID as an integer. Encode as Base58 to get the usual string version.

BrickletLaserRangeFinderV2.get_identity
Function ID:

255

Request:

empty payload

Response:
  • uid -- char[8]
  • connected_uid -- char[8]
  • position -- char
  • hardware_version -- uint8[3]
  • firmware_version -- uint8[3]
  • device_identifier -- uint16

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' or 'd'.

The device identifier numbers can be found here

Callback Configuration Functions

BrickletLaserRangeFinderV2.set_distance_callback_configuration
Function ID:

2

Request:
  • period -- uint32
  • value_has_to_change -- bool
  • option -- char
  • min -- int16
  • max -- int16
Response:

no response

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

If the value has to change-parameter is set to true, the callback is only triggered after the value has changed. If the value didn't change within the period, the callback is triggered immediately on change.

If it is set to false, the callback is continuously triggered with the period, independent of the value.

It is furthermore possible to constrain the callback with thresholds.

The option-parameter together with min/max sets a threshold for the CALLBACK_DISTANCE callback.

The following options are possible:

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

If the option is set to 'x' (threshold turned off) the callback is triggered with the fixed period.

The default value is (0, false, 'x', 0, 0).

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

  • x: off, for option
  • o: outside, for option
  • i: inside, for option
  • <: smaller, for option
  • >: greater, for option
BrickletLaserRangeFinderV2.get_distance_callback_configuration
Function ID:

3

Request:

empty payload

Response:
  • period -- uint32
  • value_has_to_change -- bool
  • option -- char
  • min -- int16
  • max -- int16

Returns the callback configuration as set by set_distance_callback_configuration.

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

  • x: off, for option
  • o: outside, for option
  • i: inside, for option
  • <: smaller, for option
  • >: greater, for option
BrickletLaserRangeFinderV2.set_velocity_callback_configuration
Function ID:

6

Request:
  • period -- uint32
  • value_has_to_change -- bool
  • option -- char
  • min -- int16
  • max -- int16
Response:

no response

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

If the value has to change-parameter is set to true, the callback is only triggered after the value has changed. If the value didn't change within the period, the callback is triggered immediately on change.

If it is set to false, the callback is continuously triggered with the period, independent of the value.

It is furthermore possible to constrain the callback with thresholds.

The option-parameter together with min/max sets a threshold for the CALLBACK_VELOCITY callback.

The following options are possible:

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

If the option is set to 'x' (threshold turned off) the callback is triggered with the fixed period.

The default value is (0, false, 'x', 0, 0).

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

  • x: off, for option
  • o: outside, for option
  • i: inside, for option
  • <: smaller, for option
  • >: greater, for option
BrickletLaserRangeFinderV2.get_velocity_callback_configuration
Function ID:

7

Request:

empty payload

Response:
  • period -- uint32
  • value_has_to_change -- bool
  • option -- char
  • min -- int16
  • max -- int16

Returns the callback configuration as set by set_velocity_callback_configuration.

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

  • x: off, for option
  • o: outside, for option
  • i: inside, for option
  • <: smaller, for option
  • >: greater, for option

Callbacks

BrickletLaserRangeFinderV2.CALLBACK_DISTANCE
Function ID:

4

Response:
  • distance -- int16

This callback is triggered periodically according to the configuration set by set_distance_callback_configuration.

The response value is the same as get_distance.

BrickletLaserRangeFinderV2.CALLBACK_VELOCITY
Function ID:

8

Response:
  • velocity -- int16

This callback is triggered periodically according to the configuration set by set_velocity_callback_configuration.

The response value is the same as get_velocity.