Python - Laser Range Finder Bricklet 2.0

This is the description of the Python API bindings 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.

An installation guide for the Python API bindings is part of their general description.

Examples

The example code below is Public Domain (CC0 1.0).

API

Generally, every method of the Python bindings can throw an tinkerforge.ip_connection.Error exception that has a value and a description property. value can have different values:

  • Error.TIMEOUT = -1
  • Error.NOT_ADDED = -6 (unused since Python bindings version 2.0.0)
  • Error.ALREADY_CONNECTED = -7
  • Error.NOT_CONNECTED = -8
  • Error.INVALID_PARAMETER = -9
  • Error.NOT_SUPPORTED = -10
  • Error.UNKNOWN_ERROR_CODE = -11
  • Error.STREAM_OUT_OF_SYNC = -12
  • Error.INVALID_UID = -13
  • Error.NON_ASCII_CHAR_IN_SECRET = -14

All methods listed below are thread-safe.

Basic Functions

BrickletLaserRangeFinderV2(uid, ipcon)
Parameters:
  • uid -- string
  • ipcon -- IPConnection

Creates an object with the unique device ID uid:

laser_range_finder_v2 = BrickletLaserRangeFinderV2("YOUR_DEVICE_UID", ipcon)

This object can then be used after the IP Connection is connected (see examples above).

BrickletLaserRangeFinderV2.get_distance()
Return type:int

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()
Return type:int

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(enable)
Parameters:enable -- bool
Return type:None

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()
Return type:bool

Returns the value as set by set_enable().

BrickletLaserRangeFinderV2.set_configuration(acquisition_count, enable_quick_termination, threshold_value, measurement_frequency)
Parameters:
  • acquisition_count -- int
  • enable_quick_termination -- bool
  • threshold_value -- int
  • measurement_frequency -- int
Return type:

None

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()
Return type:(int, bool, int, int)

Returns the configuration as set by set_configuration().

The returned namedtuple has the variables acquisition_count, enable_quick_termination, threshold_value and measurement_frequency.

BrickletLaserRangeFinderV2.set_distance_led_config(config)
Parameters:config -- int
Return type:None

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 constants are available for this function:

  • BrickletLaserRangeFinderV2.DISTANCE_LED_CONFIG_OFF = 0
  • BrickletLaserRangeFinderV2.DISTANCE_LED_CONFIG_ON = 1
  • BrickletLaserRangeFinderV2.DISTANCE_LED_CONFIG_SHOW_HEARTBEAT = 2
  • BrickletLaserRangeFinderV2.DISTANCE_LED_CONFIG_SHOW_DISTANCE = 3
BrickletLaserRangeFinderV2.get_distance_led_config()
Return type:int

Returns the LED configuration as set by set_distance_led_config()

The following constants are available for this function:

  • BrickletLaserRangeFinderV2.DISTANCE_LED_CONFIG_OFF = 0
  • BrickletLaserRangeFinderV2.DISTANCE_LED_CONFIG_ON = 1
  • BrickletLaserRangeFinderV2.DISTANCE_LED_CONFIG_SHOW_HEARTBEAT = 2
  • BrickletLaserRangeFinderV2.DISTANCE_LED_CONFIG_SHOW_DISTANCE = 3

Advanced Functions

BrickletLaserRangeFinderV2.set_moving_average(distance_average_length, velocity_average_length)
Parameters:
  • distance_average_length -- int
  • velocity_average_length -- int
Return type:

None

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()
Return type:(int, int)

Returns the length moving average as set by set_moving_average().

The returned namedtuple has the variables distance_average_length and velocity_average_length.

BrickletLaserRangeFinderV2.set_offset_calibration(offset)
Parameters:offset -- int
Return type:None

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()
Return type:int

Returns the offset value as set by set_offset_calibration().

BrickletLaserRangeFinderV2.get_api_version()
Return type:[int, int, int]

Returns the version of the API definition (major, minor, revision) implemented by this API bindings. This is neither the release version of this API bindings nor does it tell you anything about the represented Brick or Bricklet.

BrickletLaserRangeFinderV2.get_response_expected(function_id)
Parameters:function_id -- int
Return type:bool

Returns the response expected flag for the function specified by the function ID parameter. It is true if the function is expected to send a response, false otherwise.

For getter functions this is enabled by default and cannot be disabled, because those functions will always send a response. For callback configuration functions it is enabled by default too, but can be disabled by set_response_expected(). For setter functions it is disabled by default and can be enabled.

Enabling the response expected flag for a setter function allows to detect timeouts and other error conditions calls of this setter as well. The device will then send a response for this purpose. If this flag is disabled for a setter function then no response is send and errors are silently ignored, because they cannot be detected.

The following constants are available for this function:

  • BrickletLaserRangeFinderV2.FUNCTION_SET_DISTANCE_CALLBACK_CONFIGURATION = 2
  • BrickletLaserRangeFinderV2.FUNCTION_SET_VELOCITY_CALLBACK_CONFIGURATION = 6
  • BrickletLaserRangeFinderV2.FUNCTION_SET_ENABLE = 9
  • BrickletLaserRangeFinderV2.FUNCTION_SET_CONFIGURATION = 11
  • BrickletLaserRangeFinderV2.FUNCTION_SET_MOVING_AVERAGE = 13
  • BrickletLaserRangeFinderV2.FUNCTION_SET_OFFSET_CALIBRATION = 15
  • BrickletLaserRangeFinderV2.FUNCTION_SET_DISTANCE_LED_CONFIG = 17
  • BrickletLaserRangeFinderV2.FUNCTION_SET_WRITE_FIRMWARE_POINTER = 237
  • BrickletLaserRangeFinderV2.FUNCTION_SET_STATUS_LED_CONFIG = 239
  • BrickletLaserRangeFinderV2.FUNCTION_RESET = 243
  • BrickletLaserRangeFinderV2.FUNCTION_WRITE_UID = 248
BrickletLaserRangeFinderV2.set_response_expected(function_id, response_expected)
Parameters:
  • function_id -- int
  • response_expected -- bool
Return type:

None

Changes the response expected flag of the function specified by the function ID parameter. This flag can only be changed for setter (default value: false) and callback configuration functions (default value: true). For getter functions it is always enabled.

Enabling the response expected flag for a setter function allows to detect timeouts and other error conditions calls of this setter as well. The device will then send a response for this purpose. If this flag is disabled for a setter function then no response is send and errors are silently ignored, because they cannot be detected.

The following constants are available for this function:

  • BrickletLaserRangeFinderV2.FUNCTION_SET_DISTANCE_CALLBACK_CONFIGURATION = 2
  • BrickletLaserRangeFinderV2.FUNCTION_SET_VELOCITY_CALLBACK_CONFIGURATION = 6
  • BrickletLaserRangeFinderV2.FUNCTION_SET_ENABLE = 9
  • BrickletLaserRangeFinderV2.FUNCTION_SET_CONFIGURATION = 11
  • BrickletLaserRangeFinderV2.FUNCTION_SET_MOVING_AVERAGE = 13
  • BrickletLaserRangeFinderV2.FUNCTION_SET_OFFSET_CALIBRATION = 15
  • BrickletLaserRangeFinderV2.FUNCTION_SET_DISTANCE_LED_CONFIG = 17
  • BrickletLaserRangeFinderV2.FUNCTION_SET_WRITE_FIRMWARE_POINTER = 237
  • BrickletLaserRangeFinderV2.FUNCTION_SET_STATUS_LED_CONFIG = 239
  • BrickletLaserRangeFinderV2.FUNCTION_RESET = 243
  • BrickletLaserRangeFinderV2.FUNCTION_WRITE_UID = 248
BrickletLaserRangeFinderV2.set_response_expected_all(response_expected)
Parameters:response_expected -- bool
Return type:None

Changes the response expected flag for all setter and callback configuration functions of this device at once.

BrickletLaserRangeFinderV2.get_spitfp_error_count()
Return type:(int, int, int, int)

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.

The returned namedtuple has the variables error_count_ack_checksum, error_count_message_checksum, error_count_frame and error_count_overflow.

BrickletLaserRangeFinderV2.set_bootloader_mode(mode)
Parameters:mode -- int
Return type:int

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 constants are available for this function:

  • BrickletLaserRangeFinderV2.BOOTLOADER_MODE_BOOTLOADER = 0
  • BrickletLaserRangeFinderV2.BOOTLOADER_MODE_FIRMWARE = 1
  • BrickletLaserRangeFinderV2.BOOTLOADER_MODE_BOOTLOADER_WAIT_FOR_REBOOT = 2
  • BrickletLaserRangeFinderV2.BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_REBOOT = 3
  • BrickletLaserRangeFinderV2.BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_ERASE_AND_REBOOT = 4
  • BrickletLaserRangeFinderV2.BOOTLOADER_STATUS_OK = 0
  • BrickletLaserRangeFinderV2.BOOTLOADER_STATUS_INVALID_MODE = 1
  • BrickletLaserRangeFinderV2.BOOTLOADER_STATUS_NO_CHANGE = 2
  • BrickletLaserRangeFinderV2.BOOTLOADER_STATUS_ENTRY_FUNCTION_NOT_PRESENT = 3
  • BrickletLaserRangeFinderV2.BOOTLOADER_STATUS_DEVICE_IDENTIFIER_INCORRECT = 4
  • BrickletLaserRangeFinderV2.BOOTLOADER_STATUS_CRC_MISMATCH = 5
BrickletLaserRangeFinderV2.get_bootloader_mode()
Return type:int

Returns the current bootloader mode, see set_bootloader_mode().

The following constants are available for this function:

  • BrickletLaserRangeFinderV2.BOOTLOADER_MODE_BOOTLOADER = 0
  • BrickletLaserRangeFinderV2.BOOTLOADER_MODE_FIRMWARE = 1
  • BrickletLaserRangeFinderV2.BOOTLOADER_MODE_BOOTLOADER_WAIT_FOR_REBOOT = 2
  • BrickletLaserRangeFinderV2.BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_REBOOT = 3
  • BrickletLaserRangeFinderV2.BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_ERASE_AND_REBOOT = 4
BrickletLaserRangeFinderV2.set_write_firmware_pointer(pointer)
Parameters:pointer -- int
Return type:None

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(data)
Parameters:data -- [int, int, ..61x.., int]
Return type:int

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(config)
Parameters:config -- int
Return type:None

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 constants are available for this function:

  • BrickletLaserRangeFinderV2.STATUS_LED_CONFIG_OFF = 0
  • BrickletLaserRangeFinderV2.STATUS_LED_CONFIG_ON = 1
  • BrickletLaserRangeFinderV2.STATUS_LED_CONFIG_SHOW_HEARTBEAT = 2
  • BrickletLaserRangeFinderV2.STATUS_LED_CONFIG_SHOW_STATUS = 3
BrickletLaserRangeFinderV2.get_status_led_config()
Return type:int

Returns the configuration as set by set_status_led_config()

The following constants are available for this function:

  • BrickletLaserRangeFinderV2.STATUS_LED_CONFIG_OFF = 0
  • BrickletLaserRangeFinderV2.STATUS_LED_CONFIG_ON = 1
  • BrickletLaserRangeFinderV2.STATUS_LED_CONFIG_SHOW_HEARTBEAT = 2
  • BrickletLaserRangeFinderV2.STATUS_LED_CONFIG_SHOW_STATUS = 3
BrickletLaserRangeFinderV2.get_chip_temperature()
Return type:int

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()
Return type:None

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(uid)
Parameters:uid -- int
Return type:None

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()
Return type:int

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

BrickletLaserRangeFinderV2.get_identity()
Return type:(str, str, chr, [int, int, int], [int, int, int], int)

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. There is also a constant for the device identifier of this Bricklet.

The returned namedtuple has the variables uid, connected_uid, position, hardware_version, firmware_version and device_identifier.

Callback Configuration Functions

BrickletLaserRangeFinderV2.register_callback(callback_id, function)
Parameters:
  • callback_id -- int
  • function -- callable
Return type:

None

Registers the given function with the given callback_id.

The available callback IDs with corresponding function signatures are listed below.

BrickletLaserRangeFinderV2.set_distance_callback_configuration(period, value_has_to_change, option, min, max)
Parameters:
  • period -- int
  • value_has_to_change -- bool
  • option -- chr
  • min -- int
  • max -- int
Return type:

None

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 constants are available for this function:

  • BrickletLaserRangeFinderV2.THRESHOLD_OPTION_OFF = 'x'
  • BrickletLaserRangeFinderV2.THRESHOLD_OPTION_OUTSIDE = 'o'
  • BrickletLaserRangeFinderV2.THRESHOLD_OPTION_INSIDE = 'i'
  • BrickletLaserRangeFinderV2.THRESHOLD_OPTION_SMALLER = '<'
  • BrickletLaserRangeFinderV2.THRESHOLD_OPTION_GREATER = '>'
BrickletLaserRangeFinderV2.get_distance_callback_configuration()
Return type:(int, bool, chr, int, int)

Returns the callback configuration as set by set_distance_callback_configuration().

The following constants are available for this function:

  • BrickletLaserRangeFinderV2.THRESHOLD_OPTION_OFF = 'x'
  • BrickletLaserRangeFinderV2.THRESHOLD_OPTION_OUTSIDE = 'o'
  • BrickletLaserRangeFinderV2.THRESHOLD_OPTION_INSIDE = 'i'
  • BrickletLaserRangeFinderV2.THRESHOLD_OPTION_SMALLER = '<'
  • BrickletLaserRangeFinderV2.THRESHOLD_OPTION_GREATER = '>'

The returned namedtuple has the variables period, value_has_to_change, option, min and max.

BrickletLaserRangeFinderV2.set_velocity_callback_configuration(period, value_has_to_change, option, min, max)
Parameters:
  • period -- int
  • value_has_to_change -- bool
  • option -- chr
  • min -- int
  • max -- int
Return type:

None

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 constants are available for this function:

  • BrickletLaserRangeFinderV2.THRESHOLD_OPTION_OFF = 'x'
  • BrickletLaserRangeFinderV2.THRESHOLD_OPTION_OUTSIDE = 'o'
  • BrickletLaserRangeFinderV2.THRESHOLD_OPTION_INSIDE = 'i'
  • BrickletLaserRangeFinderV2.THRESHOLD_OPTION_SMALLER = '<'
  • BrickletLaserRangeFinderV2.THRESHOLD_OPTION_GREATER = '>'
BrickletLaserRangeFinderV2.get_velocity_callback_configuration()
Return type:(int, bool, chr, int, int)

Returns the callback configuration as set by set_velocity_callback_configuration().

The following constants are available for this function:

  • BrickletLaserRangeFinderV2.THRESHOLD_OPTION_OFF = 'x'
  • BrickletLaserRangeFinderV2.THRESHOLD_OPTION_OUTSIDE = 'o'
  • BrickletLaserRangeFinderV2.THRESHOLD_OPTION_INSIDE = 'i'
  • BrickletLaserRangeFinderV2.THRESHOLD_OPTION_SMALLER = '<'
  • BrickletLaserRangeFinderV2.THRESHOLD_OPTION_GREATER = '>'

The returned namedtuple has the variables period, value_has_to_change, option, min and max.

Callbacks

Callbacks can be registered to receive time critical or recurring data from the device. The registration is done with the register_callback() function of the device object. The first parameter is the callback ID and the second parameter the callback function:

def my_callback(param):
    print(param)

laser_range_finder_v2.register_callback(BrickletLaserRangeFinderV2.CALLBACK_EXAMPLE, my_callback)

The available constants with inherent number and type of parameters are described below.

Note

Using callbacks for recurring events is always preferred compared to using getters. It will use less USB bandwidth and the latency will be a lot better, since there is no round trip time.

BrickletLaserRangeFinderV2.CALLBACK_DISTANCE
Parameters:distance -- int

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

The parameter is the same as get_distance().

BrickletLaserRangeFinderV2.CALLBACK_VELOCITY
Parameters:velocity -- int

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

The parameter is the same as get_velocity().

Constants

BrickletLaserRangeFinderV2.DEVICE_IDENTIFIER

This constant is used to identify a Laser Range Finder Bricklet 2.0.

The get_identity() function and the IPConnection.CALLBACK_ENUMERATE callback of the IP Connection have a device_identifier parameter to specify the Brick's or Bricklet's type.

BrickletLaserRangeFinderV2.DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Laser Range Finder Bricklet 2.0.