Modbus - LED Strip Bricklet

This is the description of the Modbus protocol for the LED Strip Bricklet. General information and technical specifications for the LED Strip Bricklet are summarized in its hardware description.

API

A general description of the Modbus protocol structure can be found here.

Basic Functions

BrickletLEDStrip.set_rgb_values
Function ID:

1

Request:
  • index -- uint16
  • length -- uint8
  • r -- uint8[16]
  • g -- uint8[16]
  • b -- uint8[16]
Response:

no response

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 (set_chip_type) and a 3-channel channel mapping (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 set_frame_duration.

Generic approach:

  • Set the frame duration to a value that represents the number of frames per second you want to achieve.
  • Set all of the LED colors for one frame.
  • Wait for the CALLBACK_FRAME_RENDERED callback.
  • Set all of the LED colors for next frame.
  • Wait for the CALLBACK_FRAME_RENDERED callback.
  • and so on.

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 set_rgb_values with index + length above the bounds is ignored completely.

BrickletLEDStrip.get_rgb_values
Function ID:

2

Request:
  • index -- uint16
  • length -- uint8
Response:
  • r -- uint8[16]
  • g -- uint8[16]
  • b -- uint8[16]

Returns RGB value with the given length starting from the given index.

The values are the last values that were set by set_rgb_values.

BrickletLEDStrip.set_frame_duration
Function ID:

3

Request:
  • duration -- uint16
Response:

no response

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 set_rgb_values.

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

BrickletLEDStrip.get_frame_duration
Function ID:

4

Request:

empty payload

Response:
  • duration -- uint16

Returns the frame duration in ms as set by set_frame_duration.

BrickletLEDStrip.get_supply_voltage
Function ID:

5

Request:

empty payload

Response:
  • voltage -- uint16

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

BrickletLEDStrip.set_clock_frequency
Function ID:

7

Request:
  • frequency -- uint32
Response:

no response

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 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).

BrickletLEDStrip.get_clock_frequency
Function ID:

8

Request:

empty payload

Response:
  • frequency -- uint32

Returns the currently used clock frequency as set by set_clock_frequency.

New in version 2.0.1 (Plugin).

BrickletLEDStrip.set_chip_type
Function ID:

9

Request:
  • chip -- uint16
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 default value is WS2801 (2801).

New in version 2.0.2 (Plugin).

The following meanings are defined for the parameters of this function:

  • 2801: ws2801, for chip
  • 2811: ws2811, for chip
  • 2812: ws2812, for chip
  • 8806: lpd8806, for chip
  • 102: apa102, for chip
BrickletLEDStrip.get_chip_type
Function ID:

10

Request:

empty payload

Response:
  • chip -- uint16

Returns the currently used chip type as set by set_chip_type.

New in version 2.0.2 (Plugin).

The following meanings are defined for the parameters of this function:

  • 2801: ws2801, for chip
  • 2811: ws2811, for chip
  • 2812: ws2812, for chip
  • 8806: lpd8806, for chip
  • 102: apa102, for chip
BrickletLEDStrip.set_rgbw_values
Function ID:

11

Request:
  • index -- uint16
  • length -- uint8
  • r -- uint8[12]
  • g -- uint8[12]
  • b -- uint8[12]
  • w -- uint8[12]
Response:

no response

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 (set_chip_type) and a 4-channel channel mapping (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 set_frame_duration.

Generic approach:

  • Set the frame duration to a value that represents the number of frames per second you want to achieve.
  • Set all of the LED colors for one frame.
  • Wait for the CALLBACK_FRAME_RENDERED callback.
  • Set all of the LED colors for next frame.
  • Wait for the CALLBACK_FRAME_RENDERED callback.
  • and so on.

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 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).

BrickletLEDStrip.get_rgbw_values
Function ID:

12

Request:
  • index -- uint16
  • length -- uint8
Response:
  • r -- uint8[12]
  • g -- uint8[12]
  • b -- uint8[12]
  • w -- uint8[12]

Returns RGBW values with the given length starting from the given index.

The values are the last values that were set by set_rgbw_values.

New in version 2.0.6 (Plugin).

BrickletLEDStrip.set_channel_mapping
Function ID:

13

Request:
  • mapping -- uint8
Response:

no response

Sets the channel mapping for the connected LEDs.

set_rgb_values and 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 set_rgb_values has to be used. Calling set_rgbw_values with a 3-channel mapping will produce incorrect results. Vice-versa if a 4-channel mapping is selected then set_rgbw_values has to be used. Calling set_rgb_values with a 4-channel mapping will produce incorrect results.

The default value is BGR (36).

New in version 2.0.6 (Plugin).

The following meanings are defined for the parameters of this function:

  • 6: rgb, for mapping
  • 9: rbg, for mapping
  • 33: brg, for mapping
  • 36: bgr, for mapping
  • 18: grb, for mapping
  • 24: gbr, for mapping
  • 27: rgbw, for mapping
  • 30: rgwb, for mapping
  • 39: rbgw, for mapping
  • 45: rbwg, for mapping
  • 54: rwgb, for mapping
  • 57: rwbg, for mapping
  • 78: grwb, for mapping
  • 75: grbw, for mapping
  • 108: gbwr, for mapping
  • 99: gbrw, for mapping
  • 120: gwbr, for mapping
  • 114: gwrb, for mapping
  • 135: brgw, for mapping
  • 141: brwg, for mapping
  • 147: bgrw, for mapping
  • 156: bgwr, for mapping
  • 177: bwrg, for mapping
  • 180: bwgr, for mapping
  • 201: wrbg, for mapping
  • 198: wrgb, for mapping
  • 216: wgbr, for mapping
  • 210: wgrb, for mapping
  • 228: wbgr, for mapping
  • 225: wbrg, for mapping
BrickletLEDStrip.get_channel_mapping
Function ID:

14

Request:

empty payload

Response:
  • mapping -- uint8

Returns the currently used channel mapping as set by set_channel_mapping.

New in version 2.0.6 (Plugin).

The following meanings are defined for the parameters of this function:

  • 6: rgb, for mapping
  • 9: rbg, for mapping
  • 33: brg, for mapping
  • 36: bgr, for mapping
  • 18: grb, for mapping
  • 24: gbr, for mapping
  • 27: rgbw, for mapping
  • 30: rgwb, for mapping
  • 39: rbgw, for mapping
  • 45: rbwg, for mapping
  • 54: rwgb, for mapping
  • 57: rwbg, for mapping
  • 78: grwb, for mapping
  • 75: grbw, for mapping
  • 108: gbwr, for mapping
  • 99: gbrw, for mapping
  • 120: gwbr, for mapping
  • 114: gwrb, for mapping
  • 135: brgw, for mapping
  • 141: brwg, for mapping
  • 147: bgrw, for mapping
  • 156: bgwr, for mapping
  • 177: bwrg, for mapping
  • 180: bwgr, for mapping
  • 201: wrbg, for mapping
  • 198: wrgb, for mapping
  • 216: wgbr, for mapping
  • 210: wgrb, for mapping
  • 228: wbgr, for mapping
  • 225: wbrg, for mapping

Advanced Functions

BrickletLEDStrip.get_identity
Function ID:

255

Request:

empty payload

Response:
  • uid -- char[8]
  • connected_uid -- char[8]
  • position -- char
  • hardware_version -- uint8[3]
  • firmware_version -- uint8[3]
  • device_identifier -- uint16

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

Callback Configuration Functions

BrickletLEDStrip.enable_frame_rendered_callback
Function ID:15
Request:empty payload
Response:no response

Enables the CALLBACK_FRAME_RENDERED callback.

By default the callback is enabled.

New in version 2.0.6 (Plugin).

BrickletLEDStrip.disable_frame_rendered_callback
Function ID:16
Request:empty payload
Response:no response

Disables the CALLBACK_FRAME_RENDERED callback.

By default the callback is enabled.

New in version 2.0.6 (Plugin).

BrickletLEDStrip.is_frame_rendered_callback_enabled
Function ID:

17

Request:

empty payload

Response:
  • enabled -- bool

Returns true if the CALLBACK_FRAME_RENDERED callback is enabled, false otherwise.

New in version 2.0.6 (Plugin).

Callbacks

BrickletLEDStrip.CALLBACK_FRAME_RENDERED
Function ID:

6

Response:
  • length -- uint16

This callback is triggered directly after a new frame is rendered. The response value 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 set_rgb_values.