Software / API Bindings / MQTT / API Reference and Examples / Bricklets / Motorized Linear Poti Bricklet

MQTT - Motorized Linear Poti Bricklet¶

This is the description of the MQTT API bindings for the Motorized Linear Poti Bricklet. General information and technical specifications for the Motorized Linear Poti Bricklet are summarized in its hardware description.

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

Examples¶

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

Simple¶

Download (example-simple.txt)

# Change XYZ to the UID of your Motorized Linear Poti Bricklet

setup:
    # Get current position
    subscribe to tinkerforge/response/motorized_linear_poti_bricklet/XYZ/get_position
    publish '' to tinkerforge/request/motorized_linear_poti_bricklet/XYZ/get_position

Callback¶

Download (example-callback.txt)

# Change XYZ to the UID of your Motorized Linear Poti Bricklet

setup:
    # Handle incoming position callbacks
    subscribe to tinkerforge/callback/motorized_linear_poti_bricklet/XYZ/position
    publish '{"register": true}' to tinkerforge/register/motorized_linear_poti_bricklet/XYZ/position # Register position callback

    # Set period for position callback to 0.05s (50ms) without a threshold
    publish '{"period": 50, "value_has_to_change": false, "option": "off", "min": 0, "max": 0}' to tinkerforge/request/motorized_linear_poti_bricklet/XYZ/set_position_callback_configuration

Motor¶

Download (example-motor.txt)

# Change XYZ to the UID of your Motorized Linear Poti Bricklet

setup:
    # Handle incoming position reached callbacks
    subscribe to tinkerforge/callback/motorized_linear_poti_bricklet/XYZ/position_reached
    publish '{"register": true}' to tinkerforge/register/motorized_linear_poti_bricklet/XYZ/position_reached # Register position_reached callback

    # Move slider smooth to the middle
    publish '{"position": 50, "drive_mode": "smooth", "hold_position": false}' to tinkerforge/request/motorized_linear_poti_bricklet/XYZ/set_motor_position

API¶

All published payloads to and from the MQTT bindings are in JSON format.

If an error occures, the bindings publish a JSON object containing the error message as member _ERROR. It is published on the corresponding response topic: .../response/... for .../request/... and .../callback/... for .../register/....

Basic Functions¶

request/motorized_linear_poti_bricklet/<UID>/get_position¶

Request:	empty payload
Response:	position – Type: int, Range: [0 to 100]

Returns the position of the linear potentiometer. The value is between 0 (slider down) and 100 (slider up).

If you want to get the value periodically, it is recommended to use the register/motorized_linear_poti_bricklet/<UID>/position callback. You can set the callback configuration with request/motorized_linear_poti_bricklet/<UID>/set_position_callback_configuration.

request/motorized_linear_poti_bricklet/<UID>/set_motor_position¶

Request:	position – Type: int, Range: [0 to 100] drive_mode – Type: int, Range: See symbols hold_position – Type: bool
Response:	no response

Sets the position of the potentiometer. The motorized potentiometer will immediately start to approach the position. Depending on the chosen drive mode, the position will either be reached as fast as possible or in a slow but smooth motion.

The position has to be between 0 (slider down) and 100 (slider up).

If you set the hold position parameter to true, the position will automatically be retained. If a user changes the position of the potentiometer, it will automatically drive back to the original set point.

If the hold position parameter is set to false, the potentiometer can be changed again by the user as soon as the set point was reached once.

The following symbols are available for this function:

For drive_mode:

"fast" = 0
"smooth" = 1

request/motorized_linear_poti_bricklet/<UID>/get_motor_position¶

Request:	empty payload
Response:	position – Type: int, Range: [0 to 100] drive_mode – Type: int, Range: See symbols hold_position – Type: bool position_reached – Type: bool

Returns the last motor position as set by request/motorized_linear_poti_bricklet/<UID>/set_motor_position. This is not the current position (use request/motorized_linear_poti_bricklet/<UID>/get_position to get the current position). This is the last used set point and configuration.

The position reached parameter is true if the position has been reached at one point. The position may have been changed again in the meantime by the user.

The following symbols are available for this function:

For drive_mode:

"fast" = 0
"smooth" = 1

Advanced Functions¶

request/motorized_linear_poti_bricklet/<UID>/calibrate¶

Request:	empty payload
Response:	no response

Starts a calibration procedure. The potentiometer will be driven to the extreme points to calibrate the potentiometer.

The calibration is saved in flash, it does not have to be called on every start up.

The Motorized Linear Poti Bricklet is already factory-calibrated during testing at Tinkerforge.

request/motorized_linear_poti_bricklet/<UID>/get_spitfp_error_count¶

Request:	empty payload
Response:	error_count_ack_checksum – Type: int, Range: [0 to 2³² - 1] error_count_message_checksum – Type: int, Range: [0 to 2³² - 1] error_count_frame – Type: int, Range: [0 to 2³² - 1] error_count_overflow – Type: int, Range: [0 to 2³² - 1]

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.

request/motorized_linear_poti_bricklet/<UID>/set_status_led_config¶

Request:	config – Type: int, Range: See symbols, Default: 3
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 symbols are available for this function:

For config:

"off" = 0
"on" = 1
"show_heartbeat" = 2
"show_status" = 3

request/motorized_linear_poti_bricklet/<UID>/get_status_led_config¶

Request:	empty payload
Response:	config – Type: int, Range: See symbols, Default: 3

Returns the configuration as set by request/motorized_linear_poti_bricklet/<UID>/set_status_led_config

The following symbols are available for this function:

For config:

"off" = 0
"on" = 1
"show_heartbeat" = 2
"show_status" = 3

request/motorized_linear_poti_bricklet/<UID>/get_chip_temperature¶

Request:	empty payload
Response:	temperature – Type: int, Unit: 1 °C, Range: [-2¹⁵ to 2¹⁵ - 1]

Returns the temperature 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.

request/motorized_linear_poti_bricklet/<UID>/reset¶

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!

request/motorized_linear_poti_bricklet/<UID>/get_identity¶

Request:

empty payload

Response:

uid – Type: string, Length: up to 8
connected_uid – Type: string, Length: up to 8
position – Type: char, Range: ["a" to "h", "z"]
hardware_version – Type: [int, ...], Length: 3

0: major – Type: int, Range: [0 to 255]
1: minor – Type: int, Range: [0 to 255]
2: revision – Type: int, Range: [0 to 255]

firmware_version – Type: [int, ...], Length: 3

0: major – Type: int, Range: [0 to 255]
1: minor – Type: int, Range: [0 to 255]
2: revision – Type: int, Range: [0 to 255]

device_identifier – Type: int, Range: [0 to 2¹⁶ - 1]
_display_name – Type: string

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. If symbolic output is not disabled, the device identifier is mapped to the corresponding name in the format used in topics.

The display name contains the Motorized Linear Poti's name in a human readable form.

Callback Configuration Functions¶

request/motorized_linear_poti_bricklet/<UID>/set_position_callback_configuration¶

Request:	period – Type: int, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0 value_has_to_change – Type: bool, Default: false option – Type: char, Range: See symbols, Default: "x" min – Type: int, Range: [0 to 2¹⁶ - 1], Default: 0 max – Type: int, Range: [0 to 2¹⁶ - 1], Default: 0
Response:	no response

The period is the period with which the register/motorized_linear_poti_bricklet/<UID>/position 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 register/motorized_linear_poti_bricklet/<UID>/position 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 following symbols are available for this function:

For option:

"off" = "x"
"outside" = "o"
"inside" = "i"
"smaller" = "<"
"greater" = ">"

request/motorized_linear_poti_bricklet/<UID>/get_position_callback_configuration¶

Request:	empty payload
Response:	period – Type: int, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0 value_has_to_change – Type: bool, Default: false option – Type: char, Range: See symbols, Default: "x" min – Type: int, Range: [0 to 2¹⁶ - 1], Default: 0 max – Type: int, Range: [0 to 2¹⁶ - 1], Default: 0

Returns the callback configuration as set by request/motorized_linear_poti_bricklet/<UID>/set_position_callback_configuration.

The following symbols are available for this function:

For option:

"off" = "x"
"outside" = "o"
"inside" = "i"
"smaller" = "<"
"greater" = ">"

request/motorized_linear_poti_bricklet/<UID>/set_position_reached_callback_configuration¶

Request:	enabled – Type: bool, Default: true
Response:	no response

Enables/Disables register/motorized_linear_poti_bricklet/<UID>/position_reached callback.

request/motorized_linear_poti_bricklet/<UID>/get_position_reached_callback_configuration¶

Request:	empty payload
Response:	enabled – Type: bool, Default: true

Returns the register/motorized_linear_poti_bricklet/<UID>/position_reached callback configuration as set by request/motorized_linear_poti_bricklet/<UID>/set_position_reached_callback_configuration.

Callbacks¶

Callbacks can be registered to receive time critical or recurring data from the device. The registration is done with the corresponding .../register/... topic and an optional suffix. This suffix can be used to deregister the callback later.

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.

register/motorized_linear_poti_bricklet/<UID>/position¶

Register Request:	register – Type: bool
Callback Response:	position – Type: int, Range: [0 to 100]

A callback can be registered for this event by publishing to the .../register/motorized_linear_poti_bricklet/<UID>/position[/<SUFFIX>] topic with the payload "true". An added callback can be removed by publishing to the same topic with the payload "false". To support multiple (de)registrations, e.g. for message filtering, an optional suffix can be used.

If the callback is triggered, a message with it's payload is published under the corresponding .../callback/motorized_linear_poti_bricklet/<UID>/position[/<SUFFIX>] topic for each registered suffix.

This callback is triggered periodically according to the configuration set by request/motorized_linear_poti_bricklet/<UID>/set_position_callback_configuration.

The callback payload is the same as request/motorized_linear_poti_bricklet/<UID>/get_position.

register/motorized_linear_poti_bricklet/<UID>/position_reached¶

Register Request:	register – Type: bool
Callback Response:	position – Type: int, Range: [0 to 100]

A callback can be registered for this event by publishing to the .../register/motorized_linear_poti_bricklet/<UID>/position_reached[/<SUFFIX>] topic with the payload "true". An added callback can be removed by publishing to the same topic with the payload "false". To support multiple (de)registrations, e.g. for message filtering, an optional suffix can be used.

If the callback is triggered, a message with it's payload is published under the corresponding .../callback/motorized_linear_poti_bricklet/<UID>/position_reached[/<SUFFIX>] topic for each registered suffix.

This callback is triggered if a new position as set by request/motorized_linear_poti_bricklet/<UID>/set_motor_position is reached.

The callback payload is the current position.

Internal Functions¶

Internal functions are used for maintenance tasks such as flashing a new firmware of changing the UID of a Bricklet. These task should be performed using Brick Viewer instead of using the internal functions directly.

request/motorized_linear_poti_bricklet/<UID>/set_bootloader_mode¶

Request:	mode – Type: int, Range: See symbols
Response:	status – Type: int, Range: See symbols

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 symbols are available for this function:

For mode:

"bootloader" = 0
"firmware" = 1
"bootloader_wait_for_reboot" = 2
"firmware_wait_for_reboot" = 3
"firmware_wait_for_erase_and_reboot" = 4

For status:

"ok" = 0
"invalid_mode" = 1
"no_change" = 2
"entry_function_not_present" = 3
"device_identifier_incorrect" = 4
"crc_mismatch" = 5

request/motorized_linear_poti_bricklet/<UID>/get_bootloader_mode¶

Request:	empty payload
Response:	mode – Type: int, Range: See symbols

Returns the current bootloader mode, see request/motorized_linear_poti_bricklet/<UID>/set_bootloader_mode.

The following symbols are available for this function:

For mode:

"bootloader" = 0
"firmware" = 1
"bootloader_wait_for_reboot" = 2
"firmware_wait_for_reboot" = 3
"firmware_wait_for_erase_and_reboot" = 4

request/motorized_linear_poti_bricklet/<UID>/set_write_firmware_pointer¶

Request:	pointer – Type: int, Unit: 1 B, Range: [0 to 2³² - 1]
Response:	no response

Sets the firmware pointer for request/motorized_linear_poti_bricklet/<UID>/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.

request/motorized_linear_poti_bricklet/<UID>/write_firmware¶

Request:	data – Type: [int, ...], Length: 64, Range: [0 to 255]
Response:	status – Type: int, Range: [0 to 255]

Writes 64 Bytes of firmware at the position as written by request/motorized_linear_poti_bricklet/<UID>/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.

request/motorized_linear_poti_bricklet/<UID>/write_uid¶

Request:	uid – Type: int, Range: [0 to 2³² - 1]
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.

request/motorized_linear_poti_bricklet/<UID>/read_uid¶

Request:	empty payload
Response:	uid – Type: int, Range: [0 to 2³² - 1]

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