Go - LED Strip Bricklet

This is the description of the Go 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 Go API bindings is part of their general description. Additional documentation can be found on godoc.org.

Examples

The example code below is Public Domain (CC0 1.0).

Simple

Download (example_simple.go)

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package main

import (
    "fmt"
    "github.com/Tinkerforge/go-api-bindings/ipconnection"
    "github.com/Tinkerforge/go-api-bindings/led_strip_bricklet"
)

const ADDR string = "localhost:4223"
const UID string = "XYZ" // Change XYZ to the UID of your LED Strip Bricklet.

func main() {
    ipcon := ipconnection.New()
    defer ipcon.Close()
    ls, _ := led_strip_bricklet.New(UID, &ipcon) // Create device object.

    ipcon.Connect(ADDR) // Connect to brickd.
    defer ipcon.Disconnect()
    // Don't use device before ipcon is connected.

    // Set first 10 LEDs to green
    ls.SetRGBValues(0, 10, [16]uint8{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
        [16]uint8{255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 0, 0, 0, 0, 0, 0},
        [16]uint8{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0})

    fmt.Print("Press enter to exit.")
    fmt.Scanln()
}

Callback

Download (example_callback.go)

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package main

import (
    "fmt"
    "github.com/Tinkerforge/go-api-bindings/ipconnection"
    "github.com/Tinkerforge/go-api-bindings/led_strip_bricklet"
)

const ADDR string = "localhost:4223"
const UID string = "XYZ" // Change XYZ to the UID of your LED Strip Bricklet.

const NUM_LEDS = 16

func main() {
    ipcon := ipconnection.New()
    defer ipcon.Close()
    ls, _ := led_strip_bricklet.New(UID, &ipcon) // Create device object.

    ipcon.Connect(ADDR) // Connect to brickd.
    defer ipcon.Disconnect()
    // Don't use device before ipcon is connected.

    // Set frame duration to 50ms (20 frames per second)
    ls.SetFrameDuration(50)

    var r [16]uint8
    g := [16]uint8{255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 0, 0, 0, 0, 0, 0}
    var b [16]uint8

    ls.SetRGBValues(0, 10, r, g, b)

    var rIndex uint8

    ls.RegisterFrameRenderedCallback(func(length uint16) {
        b[rIndex] = 0
        if rIndex == NUM_LEDS-1 {
            rIndex = 0
        } else {
            rIndex++
        }
        b[rIndex] = 255
        ls.SetRGBValues(0, NUM_LEDS, r, g, b)
    })

    fmt.Print("Press enter to exit.")
    fmt.Scanln()
}

API

The LED Strip Bricklet API is defined in the package github.com/Tinkerforge/go-api-bindings/led_strip_bricklet

Nearly every function of the Go bindings can return an DeviceError, implementing the error interface. The error can have one of the following values:

  • DeviceErrorSuccess = 0
  • DeviceErrorInvalidParameter = 1
  • DeviceErrorFunctionNotSupported = 2
  • DeviceErrorUnknownError = 3

which correspond to the values returned from Bricks and Bricklets.

All functions listed below are thread-safe.

Basic Functions

func NewLEDStripBricklet(uid string, ipcon *IPConnection) (device LEDStripBricklet, err error)

Creates a new LEDStripBricklet object with the unique device ID uid and adds it to the IPConnection ipcon:

This device object can be used after the IPConnection has been connected (see examples above).

func (*LEDStripBricklet) SetRGBValues(index uint16, length uint8, r [16]uint8, g [16]uint8, b [16]uint8) (err error)

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 (SetChipType()) and a 3-channel channel mapping (SetChannelMapping()) 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 SetFrameDuration().

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 RegisterFrameRenderedCallback callback.
  • Set all of the LED colors for next frame.
  • Wait for the RegisterFrameRenderedCallback 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 SetRGBValues() with index + length above the bounds is ignored completely.

func (*LEDStripBricklet) GetRGBValues(index uint16, length uint8) (r [16]uint8, g [16]uint8, b [16]uint8, err error)

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

The values are the last values that were set by SetRGBValues().

func (*LEDStripBricklet) SetFrameDuration(duration uint16) (err error)

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 SetRGBValues().

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

func (*LEDStripBricklet) GetFrameDuration() (duration uint16, err error)

Returns the frame duration in ms as set by SetFrameDuration().

func (*LEDStripBricklet) GetSupplyVoltage() (voltage uint16, err error)

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

func (*LEDStripBricklet) SetClockFrequency(frequency uint32) (err error)

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 GetClockFrequency().

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).

func (*LEDStripBricklet) GetClockFrequency() (frequency uint32, err error)

Returns the currently used clock frequency as set by SetClockFrequency().

New in version 2.0.1 (Plugin).

func (*LEDStripBricklet) SetChipType(chip ChipType) (err error)

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 constants are available for this function:

  • ChipTypeWS2801 = 2801
  • ChipTypeWS2811 = 2811
  • ChipTypeWS2812 = 2812
  • ChipTypeLPD8806 = 8806
  • ChipTypeAPA102 = 102

New in version 2.0.2 (Plugin).

func (*LEDStripBricklet) GetChipType() (chip ChipType, err error)

Returns the currently used chip type as set by SetChipType().

The following constants are available for this function:

  • ChipTypeWS2801 = 2801
  • ChipTypeWS2811 = 2811
  • ChipTypeWS2812 = 2812
  • ChipTypeLPD8806 = 8806
  • ChipTypeAPA102 = 102

New in version 2.0.2 (Plugin).

func (*LEDStripBricklet) SetRGBWValues(index uint16, length uint8, r [12]uint8, g [12]uint8, b [12]uint8, w [12]uint8) (err error)

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 (SetChipType()) and a 4-channel channel mapping (SetChannelMapping()) 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 SetFrameDuration().

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 RegisterFrameRenderedCallback callback.
  • Set all of the LED colors for next frame.
  • Wait for the RegisterFrameRenderedCallback 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 SetRGBWValues() 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).

func (*LEDStripBricklet) GetRGBWValues(index uint16, length uint8) (r [12]uint8, g [12]uint8, b [12]uint8, w [12]uint8, err error)

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

The values are the last values that were set by SetRGBWValues().

New in version 2.0.6 (Plugin).

func (*LEDStripBricklet) SetChannelMapping(mapping ChannelMapping) (err error)

Sets the channel mapping for the connected LEDs.

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

The default value is BGR (36).

The following constants are available for this function:

  • ChannelMappingRGB = 6
  • ChannelMappingRBG = 9
  • ChannelMappingBRG = 33
  • ChannelMappingBGR = 36
  • ChannelMappingGRB = 18
  • ChannelMappingGBR = 24
  • ChannelMappingRGBW = 27
  • ChannelMappingRGWB = 30
  • ChannelMappingRBGW = 39
  • ChannelMappingRBWG = 45
  • ChannelMappingRWGB = 54
  • ChannelMappingRWBG = 57
  • ChannelMappingGRWB = 78
  • ChannelMappingGRBW = 75
  • ChannelMappingGBWR = 108
  • ChannelMappingGBRW = 99
  • ChannelMappingGWBR = 120
  • ChannelMappingGWRB = 114
  • ChannelMappingBRGW = 135
  • ChannelMappingBRWG = 141
  • ChannelMappingBGRW = 147
  • ChannelMappingBGWR = 156
  • ChannelMappingBWRG = 177
  • ChannelMappingBWGR = 180
  • ChannelMappingWRBG = 201
  • ChannelMappingWRGB = 198
  • ChannelMappingWGBR = 216
  • ChannelMappingWGRB = 210
  • ChannelMappingWBGR = 228
  • ChannelMappingWBRG = 225

New in version 2.0.6 (Plugin).

func (*LEDStripBricklet) GetChannelMapping() (mapping ChannelMapping, err error)

Returns the currently used channel mapping as set by SetChannelMapping().

The following constants are available for this function:

  • ChannelMappingRGB = 6
  • ChannelMappingRBG = 9
  • ChannelMappingBRG = 33
  • ChannelMappingBGR = 36
  • ChannelMappingGRB = 18
  • ChannelMappingGBR = 24
  • ChannelMappingRGBW = 27
  • ChannelMappingRGWB = 30
  • ChannelMappingRBGW = 39
  • ChannelMappingRBWG = 45
  • ChannelMappingRWGB = 54
  • ChannelMappingRWBG = 57
  • ChannelMappingGRWB = 78
  • ChannelMappingGRBW = 75
  • ChannelMappingGBWR = 108
  • ChannelMappingGBRW = 99
  • ChannelMappingGWBR = 120
  • ChannelMappingGWRB = 114
  • ChannelMappingBRGW = 135
  • ChannelMappingBRWG = 141
  • ChannelMappingBGRW = 147
  • ChannelMappingBGWR = 156
  • ChannelMappingBWRG = 177
  • ChannelMappingBWGR = 180
  • ChannelMappingWRBG = 201
  • ChannelMappingWRGB = 198
  • ChannelMappingWGBR = 216
  • ChannelMappingWGRB = 210
  • ChannelMappingWBGR = 228
  • ChannelMappingWBRG = 225

New in version 2.0.6 (Plugin).

Advanced Functions

func (*LEDStripBricklet) GetAPIVersion() (apiVersion [3]uint8, err error)

Returns the version of the API definition (major, minor, revision) implemented by this API bindings. This is neither the release version of this API bindings nor does it tell you anything about the represented Brick or Bricklet.

func (*LEDStripBricklet) GetResponseExpected(functionId uint8) (responseExpected bool, err error)

Returns the response expected flag for the function specified by the function ID parameter. It is true if the function is expected to send a response, false otherwise.

For getter functions this is enabled by default and cannot be disabled, because those functions will always send a response. For callback configuration functions it is enabled by default too, but can be disabled by SetResponseExpected(). For setter functions it is disabled by default and can be enabled.

Enabling the response expected flag for a setter function allows to detect timeouts and other error conditions calls of this setter as well. The device will then send a response for this purpose. If this flag is disabled for a setter function then no response is send and errors are silently ignored, because they cannot be detected.

See SetResponseExpected() for the list of function ID constants available for this function.

func (*LEDStripBricklet) SetResponseExpected(functionId uint8, responseExpected bool) (err error)

Changes the response expected flag of the function specified by the function ID parameter. This flag can only be changed for setter (default value: false) and callback configuration functions (default value: true). For getter functions it is always enabled.

Enabling the response expected flag for a setter function allows to detect timeouts and other error conditions calls of this setter as well. The device will then send a response for this purpose. If this flag is disabled for a setter function then no response is send and errors are silently ignored, because they cannot be detected.

The following function ID constants are available for this function:

  • FunctionSetRGBValues = 1
  • FunctionSetFrameDuration = 3
  • FunctionSetClockFrequency = 7
  • FunctionSetChipType = 9
  • FunctionSetRGBWValues = 11
  • FunctionSetChannelMapping = 13
  • FunctionEnableFrameRenderedCallback = 15
  • FunctionDisableFrameRenderedCallback = 16
func (*LEDStripBricklet) SetResponseExpectedAll(responseExpected bool) (err error)

Changes the response expected flag for all setter and callback configuration functions of this device at once.

func (*LEDStripBricklet) GetIdentity() (uid string, connectedUid string, position rune, hardwareVersion [3]uint8, firmwareVersion [3]uint8, deviceIdentifier uint16, err error)

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. There is also a constant for the device identifier of this Bricklet.

Callback Configuration Functions

func (*LEDStripBricklet) EnableFrameRenderedCallback() (err error)

Enables the RegisterFrameRenderedCallback callback.

By default the callback is enabled.

New in version 2.0.6 (Plugin).

func (*LEDStripBricklet) DisableFrameRenderedCallback() (err error)

Disables the RegisterFrameRenderedCallback callback.

By default the callback is enabled.

New in version 2.0.6 (Plugin).

func (*LEDStripBricklet) IsFrameRenderedCallbackEnabled() (enabled bool, err error)

Returns true if the RegisterFrameRenderedCallback 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*Callback function, which returns a unique callback ID. This ID 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.

func (*LEDStripBricklet) RegisterFrameRenderedCallback(func(length uint16)) (registrationId uint64)

A callback can be registered for this event with the RegisterFrameRenderedCallback() function. This function returns the ID of the registered callback. An added callback can be removed with the DeregisterFrameRenderedCallback(registrationId uint64) function.

This callback is triggered directly after a new frame is rendered. The callback parameter 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 SetRGBValues().

Constants

led_strip_bricklet.DeviceIdentifier

This constant is used to identify a LED Strip Bricklet.

The GetIdentity() function and the (*IPConnection) RegisterEnumerateCallback callback of the IPConnection have a deviceIdentifier parameter to specify the Brick's or Bricklet's type.

led_strip_bricklet.DeviceDisplayName

This constant represents the human readable name of a LED Strip Bricklet.