MQTT - LED Strip Bricklet 2.0

This is the description of the MQTT API bindings for the LED Strip Bricklet 2.0. General information and technical specifications for the LED Strip Bricklet 2.0 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 LED Strip Bricklet 2.0

setup:
    # Set first 3 LEDs to red, green and blue
    publish '{"index": 0, "value": [255,0,0,0,255,0,0,0,255]}' to tinkerforge/request/led_strip_v2_bricklet/XYZ/set_led_values 

Callback

Download (example-callback.txt)

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# FIXME: This example is incomplete

# Change XYZ to the UID of your LED Strip Bricklet 2.0

setup:
    # Set frame duration to 50ms (20 frames per second)
    publish '{"duration": 50}' to tinkerforge/request/led_strip_v2_bricklet/XYZ/set_frame_duration 
    # Use frame started callback to move the active LED every frame
    subscribe to tinkerforge/callback/led_strip_v2_bricklet/XYZ/frame_started

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 attribute "_ERROR". It is published on the corresponding response topic: .../response/... for .../request/... and .../callback/... for .../register/....

Basic Functions

request/led_strip_v2_bricklet/<UID>/set_led_values
Request payload:
  • index -- int
  • value -- [int,...]

Sets the RGB(W) values for the LEDs starting from index. You can set at most 2048 RGB values or 1536 RGBW values.

To make the colors show correctly you need to configure the chip type (see request/led_strip_v2_bricklet/<UID>/set_chip_type) and a channel mapping (see request/led_strip_v2_bricklet/<UID>/set_channel_mapping) according to the connected LEDs.

If the channel mapping has 3 colors, you need to give the data in the sequence RGBRGBRGB... if the channel mapping has 4 colors you need to give data in the sequence RGBWRGBWRGBW...

The data is double buffered and the colors will be transfered to the LEDs when the next frame duration ends (see request/led_strip_v2_bricklet/<UID>/set_frame_duration).

Generic approach:

This approach ensures that you can change the LED colors with a fixed frame rate.

request/led_strip_v2_bricklet/<UID>/get_led_values
Request payload:
  • index -- int
  • length -- int
Response payload:
  • value -- [int,...]

Returns the RGB(W) values as set by request/led_strip_v2_bricklet/<UID>/set_led_values.

request/led_strip_v2_bricklet/<UID>/set_frame_duration
Request payload:
  • duration -- int

Sets the frame duration in ms.

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

For an explanation of the general approach see request/led_strip_v2_bricklet/<UID>/set_led_values.

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

request/led_strip_v2_bricklet/<UID>/get_frame_duration
Response payload:
  • duration -- int

Returns the frame duration in ms as set by request/led_strip_v2_bricklet/<UID>/set_frame_duration.

request/led_strip_v2_bricklet/<UID>/get_supply_voltage
Response payload:
  • voltage -- int

Returns the current supply voltage of the LEDs. The voltage is given in mV.

request/led_strip_v2_bricklet/<UID>/set_clock_frequency
Request payload:
  • frequency -- int

Sets the frequency of the clock in Hz. The range is 10000Hz (10kHz) up to 2000000Hz (2MHz).

The Bricklet will choose the nearest achievable frequency, which may be off by a few Hz. You can get the exact frequency that is used by calling request/led_strip_v2_bricklet/<UID>/get_clock_frequency.

If you have problems with flickering LEDs, they may be bits flipping. You can fix this by either making the connection between the LEDs and the Bricklet shorter or by reducing the frequency.

With a decreasing frequency your maximum frames per second will decrease too.

The default value is 1.66MHz.

request/led_strip_v2_bricklet/<UID>/get_clock_frequency
Response payload:
  • frequency -- int

Returns the currently used clock frequency as set by request/led_strip_v2_bricklet/<UID>/set_clock_frequency.

request/led_strip_v2_bricklet/<UID>/set_chip_type
Request payload:
  • chip -- int (has symbols)

Sets the type of the LED driver chip. We currently support the chips

  • WS2801,
  • WS2811,
  • WS2812 / SK6812 / NeoPixel RGB,
  • SK6812RGBW / NeoPixel RGBW (Chip Type = WS2812),
  • LPD8806 and
  • APA102 / DotStar.

The default value is WS2801 (2801).

The following symbols are available for this function:

for chip:

  • "WS2801" = 2801
  • "WS2811" = 2811
  • "WS2812" = 2812
  • "LPD8806" = 8806
  • "APA102" = 102
request/led_strip_v2_bricklet/<UID>/get_chip_type
Response payload:
  • chip -- int (has symbols)

Returns the currently used chip type as set by request/led_strip_v2_bricklet/<UID>/set_chip_type.

The following symbols are available for this function:

for chip:

  • "WS2801" = 2801
  • "WS2811" = 2811
  • "WS2812" = 2812
  • "LPD8806" = 8806
  • "APA102" = 102
request/led_strip_v2_bricklet/<UID>/set_channel_mapping
Request payload:
  • mapping -- int (has symbols)

Sets the channel mapping for the connected LEDs.

If the mapping has 4 colors, the function request/led_strip_v2_bricklet/<UID>/set_led_values expects 4 values per pixel and if the mapping has 3 colors it expects 3 values per pixel.

The function always expects the order RGB(W). The connected LED driver chips might have their 3 or 4 channels in a different order. For example, the WS2801 chips typically use BGR order, then WS2812 chips typically use GRB order and the APA102 chips typically use WBGR order.

The APA102 chips are special. They have three 8-bit channels for RGB and an additional 5-bit channel for the overall brightness of the RGB LED making them 4-channel chips. Internally the brightness channel is the first channel, therefore one of the Wxyz channel mappings should be used. Then the W channel controls the brightness.

The default value is BGR (36).

The following symbols are available for this function:

for mapping:

  • "RGB" = 6
  • "RBG" = 9
  • "BRG" = 33
  • "BGR" = 36
  • "GRB" = 18
  • "GBR" = 24
  • "RGBW" = 27
  • "RGWB" = 30
  • "RBGW" = 39
  • "RBWG" = 45
  • "RWGB" = 54
  • "RWBG" = 57
  • "GRWB" = 78
  • "GRBW" = 75
  • "GBWR" = 108
  • "GBRW" = 99
  • "GWBR" = 120
  • "GWRB" = 114
  • "BRGW" = 135
  • "BRWG" = 141
  • "BGRW" = 147
  • "BGWR" = 156
  • "BWRG" = 177
  • "BWGR" = 180
  • "WRBG" = 201
  • "WRGB" = 198
  • "WGBR" = 216
  • "WGRB" = 210
  • "WBGR" = 228
  • "WBRG" = 225
request/led_strip_v2_bricklet/<UID>/get_channel_mapping
Response payload:
  • mapping -- int (has symbols)

Returns the currently used channel mapping as set by request/led_strip_v2_bricklet/<UID>/set_channel_mapping.

The following symbols are available for this function:

for mapping:

  • "RGB" = 6
  • "RBG" = 9
  • "BRG" = 33
  • "BGR" = 36
  • "GRB" = 18
  • "GBR" = 24
  • "RGBW" = 27
  • "RGWB" = 30
  • "RBGW" = 39
  • "RBWG" = 45
  • "RWGB" = 54
  • "RWBG" = 57
  • "GRWB" = 78
  • "GRBW" = 75
  • "GBWR" = 108
  • "GBRW" = 99
  • "GWBR" = 120
  • "GWRB" = 114
  • "BRGW" = 135
  • "BRWG" = 141
  • "BGRW" = 147
  • "BGWR" = 156
  • "BWRG" = 177
  • "BWGR" = 180
  • "WRBG" = 201
  • "WRGB" = 198
  • "WGBR" = 216
  • "WGRB" = 210
  • "WBGR" = 228
  • "WBRG" = 225

Advanced Functions

request/led_strip_v2_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/led_strip_v2_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/led_strip_v2_bricklet/<UID>/get_bootloader_mode
Response payload:
  • mode -- int (has symbols)

Returns the current bootloader mode, see request/led_strip_v2_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/led_strip_v2_bricklet/<UID>/set_write_firmware_pointer
Request payload:
  • pointer -- int

Sets the firmware pointer for request/led_strip_v2_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/led_strip_v2_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/led_strip_v2_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/led_strip_v2_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/led_strip_v2_bricklet/<UID>/get_status_led_config
Response payload:
  • config -- int (has symbols)

Returns the configuration as set by request/led_strip_v2_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/led_strip_v2_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/led_strip_v2_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/led_strip_v2_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/led_strip_v2_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/led_strip_v2_bricklet/<UID>/get_identity
Response payload:
  • uid -- string
  • connected_uid -- string
  • position -- char
  • 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 LED Strip 2.0's name in a human readable form.

Callback Configuration Functions

request/led_strip_v2_bricklet/<UID>/set_frame_started_callback_configuration
Request payload:
  • enable -- bool

Enables/disables the register/led_strip_v2_bricklet/<UID>/frame_started callback.

By default the callback is enabled.

request/led_strip_v2_bricklet/<UID>/get_frame_started_callback_configuration
Response payload:
  • enable -- bool

Returns the configuration as set by request/led_strip_v2_bricklet/<UID>/set_frame_started_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/led_strip_v2_bricklet/<UID>/frame_started
Request payload:
  • register -- bool
Response payload:
  • length -- int

A callback can be registered for this event by publishing to the .../register/led_strip_v2_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/led_strip_v2_bricklet/<UID>/frame_started[/<SUFFIX>] topic for each registered suffix.

This callback is triggered directly after a new frame render is started. The callback payload is the number of LEDs in that frame.

You should send the data for the next frame directly after this callback was triggered.

For an explanation of the general approach see request/led_strip_v2_bricklet/<UID>/set_led_values.