MQTT - LED Strip Bricklet

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

setup:
    # Set first 10 LEDs to green
    publish '{"index": 0, "length": 10, "r": [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0], "g": [255,255,255,255,255,255,255,255,255,255,0,0,0,0,0,0], "b": [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]}' to tinkerforge/request/led_strip_bricklet/XYZ/set_rgb_values

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/led_strip_bricklet/<UID>/set_rgb_values
Request:
  • index – Type: int, Range: [0 to 319]
  • length – Type: int, Range: [0 to 16]
  • r – Type: [int, ...], Length: 16, Range: [0 to 255]
  • g – Type: [int, ...], Length: 16, Range: [0 to 255]
  • b – Type: [int, ...], Length: 16, Range: [0 to 255]
Response:
  • no response

Sets length RGB values for the LEDs starting from index.

To make the colors show correctly you need to configure the chip type (request/led_strip_bricklet/<UID>/set_chip_type) and a 3-channel channel mapping (request/led_strip_bricklet/<UID>/set_channel_mapping) according to the connected LEDs.

Example: If you set

  • index to 5,
  • length to 3,
  • r to [255, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
  • g to [0, 255, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0] and
  • b to [0, 0, 255, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]

the LED with index 5 will be red, 6 will be green and 7 will be blue.

Note

Depending on the LED circuitry colors can be permuted.

The colors will be transfered to actual LEDs when the next frame duration ends, see request/led_strip_bricklet/<UID>/set_frame_duration.

Generic approach:

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

The actual number of controllable LEDs depends on the number of free Bricklet ports. See here for more information. A call of request/led_strip_bricklet/<UID>/set_rgb_values with index + length above the bounds is ignored completely.

request/led_strip_bricklet/<UID>/get_rgb_values
Request:
  • index – Type: int, Range: [0 to 319]
  • length – Type: int, Range: [0 to 16]
Response:
  • r – Type: [int, ...], Length: 16, Range: [0 to 255]
  • g – Type: [int, ...], Length: 16, Range: [0 to 255]
  • b – Type: [int, ...], Length: 16, Range: [0 to 255]

Returns length R, G and B values starting from the given LED index.

The values are the last values that were set by request/led_strip_bricklet/<UID>/set_rgb_values.

request/led_strip_bricklet/<UID>/set_frame_duration
Request:
  • duration – Type: int, Unit: 1 ms, Range: [0 to 216 - 1], Default: 100
Response:
  • no response

Sets the frame duration.

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_bricklet/<UID>/set_rgb_values.

request/led_strip_bricklet/<UID>/get_frame_duration
Request:
  • empty payload
Response:
  • duration – Type: int, Unit: 1 ms, Range: [0 to 216 - 1], Default: 100

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

request/led_strip_bricklet/<UID>/get_supply_voltage
Request:
  • empty payload
Response:
  • voltage – Type: int, Unit: 1 mV, Range: [0 to 216 - 1]

Returns the current supply voltage of the LEDs.

request/led_strip_bricklet/<UID>/set_clock_frequency
Request:
  • frequency – Type: int, Unit: 1 Hz, Range: [10000 to 2000000], Default: 1666666
Response:
  • no response

Sets the frequency of the clock.

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_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.

Note

The frequency in firmware version 2.0.0 is fixed at 2MHz.

New in version 2.0.1 (Plugin).

request/led_strip_bricklet/<UID>/get_clock_frequency
Request:
  • empty payload
Response:
  • frequency – Type: int, Unit: 1 Hz, Range: [10000 to 2000000], Default: 1666666

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

New in version 2.0.1 (Plugin).

request/led_strip_bricklet/<UID>/set_chip_type
Request:
  • chip – Type: int, Range: See symbols, Default: 2801
Response:
  • no response

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 following symbols are available for this function:

For chip:

  • "ws2801" = 2801
  • "ws2811" = 2811
  • "ws2812" = 2812
  • "lpd8806" = 8806
  • "apa102" = 102

New in version 2.0.2 (Plugin).

request/led_strip_bricklet/<UID>/get_chip_type
Request:
  • empty payload
Response:
  • chip – Type: int, Range: See symbols, Default: 2801

Returns the currently used chip type as set by request/led_strip_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

New in version 2.0.2 (Plugin).

request/led_strip_bricklet/<UID>/set_rgbw_values
Request:
  • index – Type: int, Range: [0 to 239]
  • length – Type: int, Range: [0 to 12]
  • r – Type: [int, ...], Length: 12, Range: [0 to 255]
  • g – Type: [int, ...], Length: 12, Range: [0 to 255]
  • b – Type: [int, ...], Length: 12, Range: [0 to 255]
  • w – Type: [int, ...], Length: 12, Range: [0 to 255]
Response:
  • no response

Sets length RGBW values for the LEDs starting from index.

To make the colors show correctly you need to configure the chip type (request/led_strip_bricklet/<UID>/set_chip_type) and a 4-channel channel mapping (request/led_strip_bricklet/<UID>/set_channel_mapping) according to the connected LEDs.

The maximum length is 12, the index goes from 0 to 239 and the rgbw values have 8 bits each.

Example: If you set

  • index to 5,
  • length to 4,
  • r to [255, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
  • g to [0, 255, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
  • b to [0, 0, 255, 0, 0, 0, 0, 0, 0, 0, 0, 0] and
  • w to [0, 0, 255, 0, 0, 0, 0, 0, 0, 0, 0, 0]

the LED with index 5 will be red, 6 will be green, 7 will be blue and 8 will be white.

Note

Depending on the LED circuitry colors can be permuted.

The colors will be transfered to actual LEDs when the next frame duration ends, see request/led_strip_bricklet/<UID>/set_frame_duration.

Generic approach:

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

The actual number of controllable LEDs depends on the number of free Bricklet ports. See here for more information. A call of request/led_strip_bricklet/<UID>/set_rgbw_values with index + length above the bounds is ignored completely.

The LPD8806 LED driver chips have 7-bit channels for RGB. Internally the LED Strip Bricklets divides the 8-bit values set using this function by 2 to make them 7-bit. Therefore, you can just use the normal value range (0-255) for LPD8806 LEDs.

The brightness channel of the APA102 LED driver chips has 5-bit. Internally the LED Strip Bricklets divides the 8-bit values set using this function by 8 to make them 5-bit. Therefore, you can just use the normal value range (0-255) for the brightness channel of APA102 LEDs.

New in version 2.0.6 (Plugin).

request/led_strip_bricklet/<UID>/get_rgbw_values
Request:
  • index – Type: int, Range: [0 to 239]
  • length – Type: int, Range: [0 to 12]
Response:
  • r – Type: [int, ...], Length: 12, Range: [0 to 255]
  • g – Type: [int, ...], Length: 12, Range: [0 to 255]
  • b – Type: [int, ...], Length: 12, Range: [0 to 255]
  • w – Type: [int, ...], Length: 12, Range: [0 to 255]

Returns length RGBW values starting from the given index.

The values are the last values that were set by request/led_strip_bricklet/<UID>/set_rgbw_values.

New in version 2.0.6 (Plugin).

request/led_strip_bricklet/<UID>/set_channel_mapping
Request:
  • mapping – Type: int, Range: See symbols, Default: 36
Response:
  • no response

Sets the channel mapping for the connected LEDs.

request/led_strip_bricklet/<UID>/set_rgb_values and request/led_strip_bricklet/<UID>/set_rgbw_values take the data in RGB(W) order. But 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, the 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.

If a 3-channel mapping is selected then request/led_strip_bricklet/<UID>/set_rgb_values has to be used. Calling request/led_strip_bricklet/<UID>/set_rgbw_values with a 3-channel mapping will produce incorrect results. Vice-versa if a 4-channel mapping is selected then request/led_strip_bricklet/<UID>/set_rgbw_values has to be used. Calling request/led_strip_bricklet/<UID>/set_rgb_values with a 4-channel mapping will produce incorrect results.

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

New in version 2.0.6 (Plugin).

request/led_strip_bricklet/<UID>/get_channel_mapping
Request:
  • empty payload
Response:
  • mapping – Type: int, Range: See symbols, Default: 36

Returns the currently used channel mapping as set by request/led_strip_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

New in version 2.0.6 (Plugin).

Advanced Functions

request/led_strip_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", "i", "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). The Raspberry Pi HAT (Zero) Brick is always at position 'i' and the Bricklet connected to an Isolator Bricklet is always as 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 LED Strip's name in a human readable form.

Callback Configuration Functions

request/led_strip_bricklet/<UID>/enable_frame_rendered_callback
Request:
  • empty payload
Response:
  • no response

Enables the register/led_strip_bricklet/<UID>/frame_rendered callback.

By default the callback is enabled.

New in version 2.0.6 (Plugin).

request/led_strip_bricklet/<UID>/disable_frame_rendered_callback
Request:
  • empty payload
Response:
  • no response

Disables the register/led_strip_bricklet/<UID>/frame_rendered callback.

By default the callback is enabled.

New in version 2.0.6 (Plugin).

request/led_strip_bricklet/<UID>/is_frame_rendered_callback_enabled
Request:
  • empty payload
Response:
  • enabled – Type: bool, Default: true

Returns true if the register/led_strip_bricklet/<UID>/frame_rendered callback is enabled, false otherwise.

New in version 2.0.6 (Plugin).

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_bricklet/<UID>/frame_rendered
Register Request:
  • register – Type: bool
Callback Response:
  • length – Type: int, Range: [0 to 320]

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

This callback is triggered directly after a new frame is rendered. The callback payload is the number of RGB or RGBW 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_bricklet/<UID>/set_rgb_values.