MQTT - Thermal Imaging Bricklet

This is the description of the MQTT API bindings for the Thermal Imaging Bricklet. General information and technical specifications for the Thermal Imaging 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).

Callback

Download (example-callback.txt)

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# Change XYZ to the UID of your Thermal Imaging Bricklet

setup:
    # Handle incoming high contrast image callbacks
    subscribe to tinkerforge/callback/thermal_imaging_bricklet/XYZ/high_contrast_image
    
    # Register high_constrast callback
    publish '{"register": true}' to tinkerforge/register/thermal_imaging_bricklet/XYZ/high_contrast_image
    
    # Enable high contrast image transfer for callback
    publish '{"config": "callback_high_contrast_image"}' to tinkerforge/request/thermal_imaging_bricklet/XYZ/set_image_transfer_config 

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/thermal_imaging_bricklet/<UID>/get_high_contrast_image
Request:
  • empty payload
Response:
  • image – Type: [int, ...], Length: 4800, Range: [0 to 255]

Returns the current high contrast image. See here for the difference between High Contrast and Temperature Image. If you don't know what to use the High Contrast Image is probably right for you.

The data is organized as a 8-bit value 80x60 pixel matrix linearized in a one-dimensional array. The data is arranged line by line from top left to bottom right.

Each 8-bit value represents one gray-scale image pixel that can directly be shown to a user on a display.

Before you can use this function you have to enable it with request/thermal_imaging_bricklet/<UID>/set_image_transfer_config.

request/thermal_imaging_bricklet/<UID>/get_temperature_image
Request:
  • empty payload
Response:
  • image – Type: [int, ...], Length: 4800, Range: [0 to 216 - 1]

Returns the current temperature image. See here for the difference between High Contrast and Temperature Image. If you don't know what to use the High Contrast Image is probably right for you.

The data is organized as a 16-bit value 80x60 pixel matrix linearized in a one-dimensional array. The data is arranged line by line from top left to bottom right.

Each 16-bit value represents one temperature measurement in either Kelvin/10 or Kelvin/100 (depending on the resolution set with request/thermal_imaging_bricklet/<UID>/set_resolution).

Before you can use this function you have to enable it with request/thermal_imaging_bricklet/<UID>/set_image_transfer_config.

request/thermal_imaging_bricklet/<UID>/get_statistics
Request:
  • empty payload
Response:
  • spotmeter_statistics – Type: [int, ...], Length: 4, Range: [0 to 216 - 1]
  • temperatures – Type: [int, ...], Length: 4, Range: [0 to 216 - 1]
  • resolution – Type: int, Range: See symbols
  • ffc_status – Type: int, Range: See symbols
  • temperature_warning – Type: [bool, ...], Length: 2

Returns the spotmeter statistics, various temperatures, current resolution and status bits.

The spotmeter statistics are:

  • Index 0: Mean Temperature.
  • Index 1: Maximum Temperature.
  • Index 2: Minimum Temperature.
  • Index 3: Pixel Count of spotmeter region of interest.

The temperatures are:

  • Index 0: Focal Plain Array temperature.
  • Index 1: Focal Plain Array temperature at last FFC (Flat Field Correction).
  • Index 2: Housing temperature.
  • Index 3: Housing temperature at last FFC.

The resolution is either 0 to 6553 Kelvin or 0 to 655 Kelvin. If the resolution is the former, the temperatures are in Kelvin/10, if it is the latter the temperatures are in Kelvin/100.

FFC (Flat Field Correction) Status:

  • FFC Never Commanded: Only seen on startup before first FFC.
  • FFC Imminent: This state is entered 2 seconds prior to initiating FFC.
  • FFC In Progress: Flat field correction is started (shutter moves in front of lens and back). Takes about 1 second.
  • FFC Complete: Shutter is in waiting position again, FFC done.

Temperature warning bits:

  • Index 0: Shutter lockout (if true shutter is locked out because temperature is outside -10°C to +65°C)
  • Index 1: Overtemperature shut down imminent (goes true 10 seconds before shutdown)

The following symbols are available for this function:

For resolution:

  • "0To6553Kelvin" = 0
  • "0To655Kelvin" = 1

For ffc_status:

  • "NeverCommanded" = 0
  • "Imminent" = 1
  • "InProgress" = 2
  • "Complete" = 3
request/thermal_imaging_bricklet/<UID>/set_resolution
Request:
  • resolution – Type: int, Range: See symbols
Response:
  • no response

Sets the resolution. The Thermal Imaging Bricklet can either measure

  • from 0 to 6553 Kelvin (-273.15°C to +6279.85°C) with 0.1°C resolution or
  • from 0 to 655 Kelvin (-273.15°C to +381.85°C) with 0.01°C resolution.

The accuracy is specified for -10°C to 450°C in the first range and -10°C and 140°C in the second range.

The default value is 0 to 655 Kelvin.

The following symbols are available for this function:

For resolution:

  • "0To6553Kelvin" = 0
  • "0To655Kelvin" = 1
request/thermal_imaging_bricklet/<UID>/get_resolution
Request:
  • empty payload
Response:
  • resolution – Type: int, Range: See symbols

Returns the resolution as set by request/thermal_imaging_bricklet/<UID>/set_resolution.

The following symbols are available for this function:

For resolution:

  • "0To6553Kelvin" = 0
  • "0To655Kelvin" = 1
request/thermal_imaging_bricklet/<UID>/set_spotmeter_config
Request:
  • region_of_interest – Type: [int, ...], Length: 4, Range: [0 to 255]
Response:
  • no response

Sets the spotmeter region of interest. The 4 values are

  • Index 0: Column start (has to be smaller then Column end).
  • Index 1: Row start (has to be smaller then Row end).
  • Index 2: Column end (has to be smaller then 80).
  • Index 3: Row end (has to be smaller then 60).

The spotmeter statistics can be read out with request/thermal_imaging_bricklet/<UID>/get_statistics.

The default region of interest is (39, 29, 40, 30).

request/thermal_imaging_bricklet/<UID>/get_spotmeter_config
Request:
  • empty payload
Response:
  • region_of_interest – Type: [int, ...], Length: 4, Range: [0 to 255]

Returns the spotmeter config as set by request/thermal_imaging_bricklet/<UID>/set_spotmeter_config.

request/thermal_imaging_bricklet/<UID>/set_high_contrast_config
Request:
  • region_of_interest – Type: [int, ...], Length: 4, Range: [0 to 255]
  • dampening_factor – Type: int, Range: [0 to 216 - 1]
  • clip_limit – Type: [int, ...], Length: 2, Range: [0 to 216 - 1]
  • empty_counts – Type: int, Range: [0 to 216 - 1]
Response:
  • no response

Sets the high contrast region of interest, dampening factor, clip limit and empty counts. This config is only used in high contrast mode (see request/thermal_imaging_bricklet/<UID>/set_image_transfer_config).

The high contrast region of interest consists of four values:

  • Index 0: Column start (has to be smaller or equal then Column end).
  • Index 1: Row start (has to be smaller then Row end).
  • Index 2: Column end (has to be smaller then 80).
  • Index 3: Row end (has to be smaller then 60).

The algorithm to generate the high contrast image is applied to this region.

Dampening Factor: This parameter is the amount of temporal dampening applied to the HEQ (history equalization) transformation function. An IIR filter of the form:

(N / 256) * previous + ((256 - N) / 256) * current

is applied, and the HEQ dampening factor represents the value N in the equation, i.e., a value that applies to the amount of influence the previous HEQ transformation function has on the current function. The lower the value of N the higher the influence of the current video frame whereas the higher the value of N the more influence the previous damped transfer function has.

Clip Limit Index 0 (AGC HEQ Clip Limit High): This parameter defines the maximum number of pixels allowed to accumulate in any given histogram bin. Any additional pixels in a given bin are clipped. The effect of this parameter is to limit the influence of highly-populated bins on the resulting HEQ transformation function.

Clip Limit Index 1 (AGC HEQ Clip Limit Low): This parameter defines an artificial population that is added to every non-empty histogram bin. In other words, if the Clip Limit Low is set to L, a bin with an actual population of X will have an effective population of L + X. Any empty bin that is nearby a populated bin will be given an artificial population of L. The effect of higher values is to provide a more linear transfer function; lower values provide a more non-linear (equalized) transfer function.

Empty Counts: This parameter specifies the maximum number of pixels in a bin that will be interpreted as an empty bin. Histogram bins with this number of pixels or less will be processed as an empty bin.

The default values are

  • Region Of Interest = (0, 0, 79, 59),
  • Dampening Factor = 64,
  • Clip Limit = (4800, 512) and
  • Empty Counts = 2.
request/thermal_imaging_bricklet/<UID>/get_high_contrast_config
Request:
  • empty payload
Response:
  • region_of_interest – Type: [int, ...], Length: 4, Range: [0 to 255]
  • dampening_factor – Type: int, Range: [0 to 216 - 1]
  • clip_limit – Type: [int, ...], Length: 2, Range: [0 to 216 - 1]
  • empty_counts – Type: int, Range: [0 to 216 - 1]

Returns the high contrast config as set by request/thermal_imaging_bricklet/<UID>/set_high_contrast_config.

Advanced Functions

request/thermal_imaging_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/thermal_imaging_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
  • "BootloaderWaitForReboot" = 2
  • "FirmwareWaitForReboot" = 3
  • "FirmwareWaitForEraseAndReboot" = 4

For status:

  • "OK" = 0
  • "InvalidMode" = 1
  • "NoChange" = 2
  • "EntryFunctionNotPresent" = 3
  • "DeviceIdentifierIncorrect" = 4
  • "CRCMismatch" = 5
request/thermal_imaging_bricklet/<UID>/get_bootloader_mode
Request:
  • empty payload
Response:
  • mode – Type: int, Range: See symbols

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

The following symbols are available for this function:

For mode:

  • "Bootloader" = 0
  • "Firmware" = 1
  • "BootloaderWaitForReboot" = 2
  • "FirmwareWaitForReboot" = 3
  • "FirmwareWaitForEraseAndReboot" = 4
request/thermal_imaging_bricklet/<UID>/set_write_firmware_pointer
Request:
  • pointer – Type: int, Range: [0 to 232 - 1]
Response:
  • no response

Sets the firmware pointer for request/thermal_imaging_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/thermal_imaging_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/thermal_imaging_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/thermal_imaging_bricklet/<UID>/set_status_led_config
Request:
  • config – Type: int, Range: See symbols
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
  • "ShowHeartbeat" = 2
  • "ShowStatus" = 3
request/thermal_imaging_bricklet/<UID>/get_status_led_config
Request:
  • empty payload
Response:
  • config – Type: int, Range: See symbols

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

The following symbols are available for this function:

For config:

  • "Off" = 0
  • "On" = 1
  • "ShowHeartbeat" = 2
  • "ShowStatus" = 3
request/thermal_imaging_bricklet/<UID>/get_chip_temperature
Request:
  • empty payload
Response:
  • temperature – Type: int, Range: [-215 to 215 - 1]

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.

request/thermal_imaging_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/thermal_imaging_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/thermal_imaging_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.

request/thermal_imaging_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
  • hardware_version – Type: [int, ...], Length: 3, Range: [0 to 255]
  • firmware_version – Type: [int, ...], Length: 3, 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' or 'd'.

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 Thermal Imaging's name in a human readable form.

Callback Configuration Functions

request/thermal_imaging_bricklet/<UID>/set_image_transfer_config
Request:
  • config – Type: int, Range: See symbols
Response:
  • no response

The necessary bandwidth of this Bricklet is too high to use getter/callback or high contrast/temperature image at the same time. You have to configure the one you want to use, the Bricklet will optimize the internal configuration accordingly.

Corresponding functions:

The default is Manual High Contrast Image (0).

The following symbols are available for this function:

For config:

  • "ManualHighContrastImage" = 0
  • "ManualTemperatureImage" = 1
  • "CallbackHighContrastImage" = 2
  • "CallbackTemperatureImage" = 3
request/thermal_imaging_bricklet/<UID>/get_image_transfer_config
Request:
  • empty payload
Response:
  • config – Type: int, Range: See symbols

Returns the image transfer config, as set by request/thermal_imaging_bricklet/<UID>/set_image_transfer_config.

The following symbols are available for this function:

For config:

  • "ManualHighContrastImage" = 0
  • "ManualTemperatureImage" = 1
  • "CallbackHighContrastImage" = 2
  • "CallbackTemperatureImage" = 3

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/thermal_imaging_bricklet/<UID>/high_contrast_image
Register Request:
  • register – Type: bool
Callback Response:
  • image – Type: [int, ...], Length: 4800, Range: [0 to 255]

A callback can be registered for this event by publishing to the .../register/thermal_imaging_bricklet/<UID>/high_contrast_image[/<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/thermal_imaging_bricklet/<UID>/high_contrast_image[/<SUFFIX>] topic for each registered suffix.

This callback is triggered with every new high contrast image if the transfer image config is configured for high contrast callback (see request/thermal_imaging_bricklet/<UID>/set_image_transfer_config).

The data is organized as a 8-bit value 80x60 pixel matrix linearized in a one-dimensional array. The data is arranged line by line from top left to bottom right.

Each 8-bit value represents one gray-scale image pixel that can directly be shown to a user on a display.

Note

If reconstructing the value fails, the callback is triggered with null for image.

register/thermal_imaging_bricklet/<UID>/temperature_image
Register Request:
  • register – Type: bool
Callback Response:
  • image – Type: [int, ...], Length: 4800, Range: [0 to 216 - 1]

A callback can be registered for this event by publishing to the .../register/thermal_imaging_bricklet/<UID>/temperature_image[/<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/thermal_imaging_bricklet/<UID>/temperature_image[/<SUFFIX>] topic for each registered suffix.

This callback is triggered with every new temperature image if the transfer image config is configured for temperature callback (see request/thermal_imaging_bricklet/<UID>/set_image_transfer_config).

The data is organized as a 16-bit value 80x60 pixel matrix linearized in a one-dimensional array. The data is arranged line by line from top left to bottom right.

Each 16-bit value represents one temperature measurement in either Kelvin/10 or Kelvin/100 (depending on the resolution set with request/thermal_imaging_bricklet/<UID>/set_resolution).

Note

If reconstructing the value fails, the callback is triggered with null for image.