MQTT - DMX Bricklet

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

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# Change XYZ to the UID of your DMX Bricklet

setup:
    # Configure Bricklet as DMX master
    publish '{"dmx_mode": "master"}' to tinkerforge/request/dmx_bricklet/XYZ/set_dmx_mode 
    
    # Write DMX frame with 3 channels
    publish '{"frame": [255,128,0]}' to tinkerforge/request/dmx_bricklet/XYZ/write_frame 

API

All published payload to an from the MQTT bindings is in the JSON format.

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

Basic Functions

request/dmx_bricklet/<UID>/set_dmx_mode
Request payload:
 
  • dmx_mode -- int (has symbols)

Sets the DMX mode to either master or slave.

Calling this function sets frame number to 0.

The default value is 0 (master).

The following symbols are available for this function:

for dmx_mode:

  • "Master" = 0
  • "Slave" = 1
request/dmx_bricklet/<UID>/get_dmx_mode
Response payload:
 
  • dmx_mode -- int (has symbols)

Returns the DMX mode, as set by request/dmx_bricklet/<UID>/set_dmx_mode.

The following symbols are available for this function:

for dmx_mode:

  • "Master" = 0
  • "Slave" = 1
request/dmx_bricklet/<UID>/write_frame
Request payload:
 
  • frame -- [int,...]

Writes a DMX frame. The maximum frame size is 512 byte. Each byte represents one channel.

The next frame can be written after the register/dmx_bricklet/<UID>/frame_started callback was called. The frame is double buffered, so a new frame can be written as soon as the writing of the prior frame starts.

The data will be transfered when the next frame duration ends, see request/dmx_bricklet/<UID>/set_frame_duration.

Generic approach:

This approach ensures that you can set new DMX data with a fixed frame rate.

This function can only be called in master mode.

request/dmx_bricklet/<UID>/read_frame
Response payload:
 
  • frame -- [int,...]
  • frame_number -- int

Returns the last frame that was written by the DMX master. The size of the array is equivalent to the number of channels in the frame. Each byte represents one channel.

The next frame is available after the register/dmx_bricklet/<UID>/frame_available callback was called.

Generic approach:

Instead of polling this function you can also use the register/dmx_bricklet/<UID>/frame callback. You can enable it with request/dmx_bricklet/<UID>/set_frame_callback_config.

The frame number starts at 0 and it is increased by one with each received frame.

This function can only be called in slave mode.

request/dmx_bricklet/<UID>/set_frame_duration
Request payload:
 
  • frame_duration -- int

Sets the duration of a frame in ms.

Example: If you want to achieve 20 frames per second, you should set the frame duration to 50ms (50ms * 20 = 1 second).

If you always want to send a frame as fast as possible you can set this value to 0.

This setting is only used in master mode.

Default value: 100ms (10 frames per second).

request/dmx_bricklet/<UID>/get_frame_duration
Response payload:
 
  • frame_duration -- int

Returns the frame duration as set by request/dmx_bricklet/<UID>/set_frame_duration.

Advanced Functions

request/dmx_bricklet/<UID>/get_frame_error_count
Response payload:
 
  • overrun_error_count -- int
  • framing_error_count -- int

Returns the current number of overrun and framing errors.

request/dmx_bricklet/<UID>/set_communication_led_config
Request payload:
 
  • config -- int (has symbols)

Sets the communication LED configuration. By default the LED shows communication traffic, 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 off.

The following symbols are available for this function:

for config:

  • "Off" = 0
  • "On" = 1
  • "ShowHeartbeat" = 2
  • "ShowCommunication" = 3
request/dmx_bricklet/<UID>/get_communication_led_config
Response payload:
 
  • config -- int (has symbols)

Returns the configuration as set by request/dmx_bricklet/<UID>/set_communication_led_config

The following symbols are available for this function:

for config:

  • "Off" = 0
  • "On" = 1
  • "ShowHeartbeat" = 2
  • "ShowCommunication" = 3
request/dmx_bricklet/<UID>/set_error_led_config
Request payload:
 
  • config -- int (has symbols)

Sets the error LED configuration.

By default the error LED turns on if there is any error (see register/dmx_bricklet/<UID>/frame_error_count callback). If you call this function with the Show-Error option again, the LED will turn off until the next error occurs.

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

If the Bricklet is in bootloader mode, the LED is off.

The following symbols are available for this function:

for config:

  • "Off" = 0
  • "On" = 1
  • "ShowHeartbeat" = 2
  • "ShowError" = 3
request/dmx_bricklet/<UID>/get_error_led_config
Response payload:
 
  • config -- int (has symbols)

Returns the configuration as set by request/dmx_bricklet/<UID>/set_error_led_config.

The following symbols are available for this function:

for config:

  • "Off" = 0
  • "On" = 1
  • "ShowHeartbeat" = 2
  • "ShowError" = 3
request/dmx_bricklet/<UID>/get_spitfp_error_count
Response payload:
 
  • error_count_ack_checksum -- int
  • error_count_message_checksum -- int
  • error_count_frame -- int
  • error_count_overflow -- 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.

request/dmx_bricklet/<UID>/set_bootloader_mode
Request payload:
 
  • mode -- int (has symbols)
Response payload:
 
  • status -- int (has 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/dmx_bricklet/<UID>/get_bootloader_mode
Response payload:
 
  • mode -- int (has symbols)

Returns the current bootloader mode, see request/dmx_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/dmx_bricklet/<UID>/set_write_firmware_pointer
Request payload:
 
  • pointer -- int

Sets the firmware pointer for request/dmx_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/dmx_bricklet/<UID>/write_firmware
Request payload:
 
  • data -- [int,... (x64)]
Response payload:
 
  • status -- int

Writes 64 Bytes of firmware at the position as written by request/dmx_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/dmx_bricklet/<UID>/set_status_led_config
Request payload:
 
  • config -- int (has symbols)

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/dmx_bricklet/<UID>/get_status_led_config
Response payload:
 
  • config -- int (has symbols)

Returns the configuration as set by request/dmx_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/dmx_bricklet/<UID>/get_chip_temperature
Response payload:
 
  • temperature -- 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.

request/dmx_bricklet/<UID>/reset

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/dmx_bricklet/<UID>/write_uid
Request payload:
 
  • uid -- int

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/dmx_bricklet/<UID>/read_uid
Response payload:
 
  • uid -- int

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

request/dmx_bricklet/<UID>/get_identity
Response payload:
 
  • uid -- string
  • connected_uid -- string
  • position -- string
  • hardware_version -- [int,int,int]
  • firmware_version -- [int,int,int]
  • device_identifier -- int (has symbols)
  • _display_name -- 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 DMX's name in a human readable form.

Callback Configuration Functions

request/dmx_bricklet/<UID>/set_frame_callback_config
Request payload:
 
  • frame_started_callback_enabled -- bool
  • frame_available_callback_enabled -- bool
  • frame_callback_enabled -- bool
  • frame_error_count_callback_enabled -- bool

Enables/Disables the different callbacks. By default the register/dmx_bricklet/<UID>/frame_started callback and register/dmx_bricklet/<UID>/frame_available callback are enabled while the register/dmx_bricklet/<UID>/frame callback and register/dmx_bricklet/<UID>/frame_error_count callback are disabled.

If you want to use the register/dmx_bricklet/<UID>/frame callback you can enable it and disable the cb:Frame Available callback at the same time. It becomes redundant in this case.

request/dmx_bricklet/<UID>/get_frame_callback_config
Response payload:
 
  • frame_started_callback_enabled -- bool
  • frame_available_callback_enabled -- bool
  • frame_callback_enabled -- bool
  • frame_error_count_callback_enabled -- bool

Returns the frame callback config as set by request/dmx_bricklet/<UID>/set_frame_callback_config.

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/dmx_bricklet/<UID>/frame_started
Request payload:
 
  • register -- bool

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

This callback is triggered as soon as a new frame write is started. You should send the data for the next frame directly after this callback was triggered.

For an explanation of the general approach see request/dmx_bricklet/<UID>/write_frame.

This callback can be enabled via request/dmx_bricklet/<UID>/set_frame_callback_config.

This callback can only be triggered in master mode.

register/dmx_bricklet/<UID>/frame_available
Request payload:
 
  • register -- bool
Response payload:
 
  • frame_number -- int

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

This callback is triggered in slave mode when a new frame was received from the DMX master and it can be read out. You have to read the frame before the master has written the next frame, see request/dmx_bricklet/<UID>/read_frame for more details.

The parameter is the frame number, it is increased by one with each received frame.

This callback can be enabled via request/dmx_bricklet/<UID>/set_frame_callback_config.

This callback can only be triggered in slave mode.

register/dmx_bricklet/<UID>/frame
Request payload:
 
  • register -- bool
Response payload:
 
  • frame -- [int,...]
  • frame_number -- int

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

This callback is called as soon as a new frame is available (written by the DMX master).

The size of the array is equivalent to the number of channels in the frame. Each byte represents one channel.

This callback can be enabled via request/dmx_bricklet/<UID>/set_frame_callback_config.

This callback can only be triggered in slave mode.

register/dmx_bricklet/<UID>/frame_error_count
Request payload:
 
  • register -- bool
Response payload:
 
  • overrun_error_count -- int
  • framing_error_count -- int

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

This callback is called if a new error occurs. It returns the current overrun and framing error count.