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)

1
2
3
4
5
# 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 attribute "_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 payload:
  • index -- int
  • length -- int
  • r -- [int,... (x16)]
  • g -- [int,... (x16)]
  • b -- [int,... (x16)]

Sets the RGB values for the LEDs with the given length 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.

The maximum length is 16, the index goes from 0 to 319 and the rgb values have 8 bits each.

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 payload:
  • index -- int
  • length -- int
Response payload:
  • r -- [int,... (x16)]
  • g -- [int,... (x16)]
  • b -- [int,... (x16)]

Returns RGB value with the given length starting from the given 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 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_bricklet/<UID>/set_rgb_values.

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

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

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

request/led_strip_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_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_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.

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
Response payload:
  • frequency -- int

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 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

New in version 2.0.2 (Plugin).

request/led_strip_bricklet/<UID>/get_chip_type
Response payload:
  • chip -- int (has symbols)

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 payload:
  • index -- int
  • length -- int
  • r -- [int,... (x12)]
  • g -- [int,... (x12)]
  • b -- [int,... (x12)]
  • w -- [int,... (x12)]

Sets the RGBW values for the LEDs with the given length 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 payload:
  • index -- int
  • length -- int
Response payload:
  • r -- [int,... (x12)]
  • g -- [int,... (x12)]
  • b -- [int,... (x12)]
  • w -- [int,... (x12)]

Returns RGBW values with the given length 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 payload:
  • mapping -- int (has symbols)

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 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

New in version 2.0.6 (Plugin).

request/led_strip_bricklet/<UID>/get_channel_mapping
Response payload:
  • mapping -- int (has symbols)

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
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's name in a human readable form.

Callback Configuration Functions

request/led_strip_bricklet/<UID>/enable_frame_rendered_callback

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

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
Response payload:
  • enabled -- bool

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
Request payload:
  • register -- bool
Response payload:
  • length -- int

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 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.