C/C++ - LED Strip Bricklet

This is the description of the C/C++ 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 C/C++ API bindings is part of their general description.

Examples

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

Simple

Download (example_simple.c)

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#include <stdio.h>

#include "ip_connection.h"
#include "bricklet_led_strip.h"

#define HOST "localhost"
#define PORT 4223
#define UID "XYZ" // Change XYZ to the UID of your LED Strip Bricklet

int main(void) {
    // Create IP connection
    IPConnection ipcon;
    ipcon_create(&ipcon);

    // Create device object
    LEDStrip ls;
    led_strip_create(&ls, UID, &ipcon);

    // Connect to brickd
    if(ipcon_connect(&ipcon, HOST, PORT) < 0) {
        fprintf(stderr, "Could not connect\n");
        return 1;
    }
    // Don't use device before ipcon is connected

    // Set first 10 LEDs to green
    uint8_t r[16] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
    uint8_t g[16] = {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 0, 0, 0, 0, 0, 0};
    uint8_t b[16] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
    led_strip_set_rgb_values(&ls, 0, 10, r, g, b);

    printf("Press key to exit\n");
    getchar();
    led_strip_destroy(&ls);
    ipcon_destroy(&ipcon); // Calls ipcon_disconnect internally
    return 0;
}

Callback

Download (example_callback.c)

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#include <stdio.h>

#include "ip_connection.h"
#include "bricklet_led_strip.h"

#define HOST "localhost"
#define PORT 4223
#define UID "XYZ" // Change XYZ to the UID of your LED Strip Bricklet
#define NUM_LEDS 16

uint8_t r[NUM_LEDS] = {0};
uint8_t g[NUM_LEDS] = {0};
uint8_t b[NUM_LEDS] = {0};
uint8_t r_index = 0;

// Use frame rendered callback to move the active LED every frame
void cb_frame_rendered(uint16_t length, void *user_data) {
    (void)length; // avoid unused parameter warning

    LEDStrip *ls = (LEDStrip *)user_data;

    b[r_index] = 0;

    if(r_index == NUM_LEDS-1) {
        r_index = 0;
    } else {
        r_index++;
    }

    b[r_index] = 255;

    // Set new data for next render cycle
    led_strip_set_rgb_values(ls, 0, NUM_LEDS, r, g, b);
}

int main(void) {
    // Create IP connection
    IPConnection ipcon;
    ipcon_create(&ipcon);

    // Create device object
    LEDStrip ls;
    led_strip_create(&ls, UID, &ipcon);

    // Connect to brickd
    if(ipcon_connect(&ipcon, HOST, PORT) < 0) {
        fprintf(stderr, "Could not connect\n");
        return 1;
    }
    // Don't use device before ipcon is connected

    // Set frame duration to 50ms (20 frames per second)
    led_strip_set_frame_duration(&ls, 50);

    // Register frame rendered callback to function cb_frame_rendered
    led_strip_register_callback(&ls,
                                LED_STRIP_CALLBACK_FRAME_RENDERED,
                                (void *)cb_frame_rendered,
                                &ls);

    // Set initial rgb values to get started
    led_strip_set_rgb_values(&ls, 0, NUM_LEDS, r, g, b);

    printf("Press key to exit\n");
    getchar();
    led_strip_destroy(&ls);
    ipcon_destroy(&ipcon); // Calls ipcon_disconnect internally
    return 0;
}

API

Every function of the C/C++ bindings returns an integer which describes an error code. Data returned from the device, when a getter is called, is handled via output parameters. These parameters are labeled with the ret_ prefix.

Possible error codes are:

  • E_OK = 0
  • E_TIMEOUT = -1
  • E_NO_STREAM_SOCKET = -2
  • E_HOSTNAME_INVALID = -3
  • E_NO_CONNECT = -4
  • E_NO_THREAD = -5
  • E_NOT_ADDED = -6 (unused since bindings version 2.0.0)
  • E_ALREADY_CONNECTED = -7
  • E_NOT_CONNECTED = -8
  • E_INVALID_PARAMETER = -9
  • E_NOT_SUPPORTED = -10
  • E_UNKNOWN_ERROR_CODE = -11
  • E_STREAM_OUT_OF_SYNC = -12
  • E_INVALID_UID = -13

as defined in ip_connection.h.

All functions listed below are thread-safe.

Basic Functions

void led_strip_create(LEDStrip *led_strip, const char *uid, IPConnection *ipcon)

Creates the device object led_strip with the unique device ID uid and adds it to the IPConnection ipcon:

LEDStrip led_strip;
led_strip_create(&led_strip, "YOUR_DEVICE_UID", &ipcon);

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

void led_strip_destroy(LEDStrip *led_strip)

Removes the device object led_strip from its IPConnection and destroys it. The device object cannot be used anymore afterwards.

int led_strip_set_rgb_values(LEDStrip *led_strip, uint16_t index, uint8_t length, uint8_t r[16], uint8_t g[16], uint8_t b[16])

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 (led_strip_set_chip_type()) and a 3-channel channel mapping (led_strip_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 led_strip_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 led_strip_set_rgb_values() with index + length above the bounds is ignored completely.

int led_strip_get_rgb_values(LEDStrip *led_strip, uint16_t index, uint8_t length, uint8_t ret_r[16], uint8_t ret_g[16], uint8_t ret_b[16])

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

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

int led_strip_set_frame_duration(LEDStrip *led_strip, uint16_t duration)

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 led_strip_set_rgb_values().

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

int led_strip_get_frame_duration(LEDStrip *led_strip, uint16_t *ret_duration)

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

int led_strip_get_supply_voltage(LEDStrip *led_strip, uint16_t *ret_voltage)

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

int led_strip_set_clock_frequency(LEDStrip *led_strip, uint32_t frequency)

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 led_strip_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).

int led_strip_get_clock_frequency(LEDStrip *led_strip, uint32_t *ret_frequency)

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

New in version 2.0.1 (Plugin).

int led_strip_set_chip_type(LEDStrip *led_strip, uint16_t chip)

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 defines are available for this function:

  • LED_STRIP_CHIP_TYPE_WS2801 = 2801
  • LED_STRIP_CHIP_TYPE_WS2811 = 2811
  • LED_STRIP_CHIP_TYPE_WS2812 = 2812
  • LED_STRIP_CHIP_TYPE_LPD8806 = 8806
  • LED_STRIP_CHIP_TYPE_APA102 = 102

New in version 2.0.2 (Plugin).

int led_strip_get_chip_type(LEDStrip *led_strip, uint16_t *ret_chip)

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

The following defines are available for this function:

  • LED_STRIP_CHIP_TYPE_WS2801 = 2801
  • LED_STRIP_CHIP_TYPE_WS2811 = 2811
  • LED_STRIP_CHIP_TYPE_WS2812 = 2812
  • LED_STRIP_CHIP_TYPE_LPD8806 = 8806
  • LED_STRIP_CHIP_TYPE_APA102 = 102

New in version 2.0.2 (Plugin).

int led_strip_set_rgbw_values(LEDStrip *led_strip, uint16_t index, uint8_t length, uint8_t r[12], uint8_t g[12], uint8_t b[12], uint8_t w[12])

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 (led_strip_set_chip_type()) and a 4-channel channel mapping (led_strip_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 led_strip_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 led_strip_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).

int led_strip_get_rgbw_values(LEDStrip *led_strip, uint16_t index, uint8_t length, uint8_t ret_r[12], uint8_t ret_g[12], uint8_t ret_b[12], uint8_t ret_w[12])

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

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

New in version 2.0.6 (Plugin).

int led_strip_set_channel_mapping(LEDStrip *led_strip, uint8_t mapping)

Sets the channel mapping for the connected LEDs.

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

The default value is BGR (36).

The following defines are available for this function:

  • LED_STRIP_CHANNEL_MAPPING_RGB = 6
  • LED_STRIP_CHANNEL_MAPPING_RBG = 9
  • LED_STRIP_CHANNEL_MAPPING_BRG = 33
  • LED_STRIP_CHANNEL_MAPPING_BGR = 36
  • LED_STRIP_CHANNEL_MAPPING_GRB = 18
  • LED_STRIP_CHANNEL_MAPPING_GBR = 24
  • LED_STRIP_CHANNEL_MAPPING_RGBW = 27
  • LED_STRIP_CHANNEL_MAPPING_RGWB = 30
  • LED_STRIP_CHANNEL_MAPPING_RBGW = 39
  • LED_STRIP_CHANNEL_MAPPING_RBWG = 45
  • LED_STRIP_CHANNEL_MAPPING_RWGB = 54
  • LED_STRIP_CHANNEL_MAPPING_RWBG = 57
  • LED_STRIP_CHANNEL_MAPPING_GRWB = 78
  • LED_STRIP_CHANNEL_MAPPING_GRBW = 75
  • LED_STRIP_CHANNEL_MAPPING_GBWR = 108
  • LED_STRIP_CHANNEL_MAPPING_GBRW = 99
  • LED_STRIP_CHANNEL_MAPPING_GWBR = 120
  • LED_STRIP_CHANNEL_MAPPING_GWRB = 114
  • LED_STRIP_CHANNEL_MAPPING_BRGW = 135
  • LED_STRIP_CHANNEL_MAPPING_BRWG = 141
  • LED_STRIP_CHANNEL_MAPPING_BGRW = 147
  • LED_STRIP_CHANNEL_MAPPING_BGWR = 156
  • LED_STRIP_CHANNEL_MAPPING_BWRG = 177
  • LED_STRIP_CHANNEL_MAPPING_BWGR = 180
  • LED_STRIP_CHANNEL_MAPPING_WRBG = 201
  • LED_STRIP_CHANNEL_MAPPING_WRGB = 198
  • LED_STRIP_CHANNEL_MAPPING_WGBR = 216
  • LED_STRIP_CHANNEL_MAPPING_WGRB = 210
  • LED_STRIP_CHANNEL_MAPPING_WBGR = 228
  • LED_STRIP_CHANNEL_MAPPING_WBRG = 225

New in version 2.0.6 (Plugin).

int led_strip_get_channel_mapping(LEDStrip *led_strip, uint8_t *ret_mapping)

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

The following defines are available for this function:

  • LED_STRIP_CHANNEL_MAPPING_RGB = 6
  • LED_STRIP_CHANNEL_MAPPING_RBG = 9
  • LED_STRIP_CHANNEL_MAPPING_BRG = 33
  • LED_STRIP_CHANNEL_MAPPING_BGR = 36
  • LED_STRIP_CHANNEL_MAPPING_GRB = 18
  • LED_STRIP_CHANNEL_MAPPING_GBR = 24
  • LED_STRIP_CHANNEL_MAPPING_RGBW = 27
  • LED_STRIP_CHANNEL_MAPPING_RGWB = 30
  • LED_STRIP_CHANNEL_MAPPING_RBGW = 39
  • LED_STRIP_CHANNEL_MAPPING_RBWG = 45
  • LED_STRIP_CHANNEL_MAPPING_RWGB = 54
  • LED_STRIP_CHANNEL_MAPPING_RWBG = 57
  • LED_STRIP_CHANNEL_MAPPING_GRWB = 78
  • LED_STRIP_CHANNEL_MAPPING_GRBW = 75
  • LED_STRIP_CHANNEL_MAPPING_GBWR = 108
  • LED_STRIP_CHANNEL_MAPPING_GBRW = 99
  • LED_STRIP_CHANNEL_MAPPING_GWBR = 120
  • LED_STRIP_CHANNEL_MAPPING_GWRB = 114
  • LED_STRIP_CHANNEL_MAPPING_BRGW = 135
  • LED_STRIP_CHANNEL_MAPPING_BRWG = 141
  • LED_STRIP_CHANNEL_MAPPING_BGRW = 147
  • LED_STRIP_CHANNEL_MAPPING_BGWR = 156
  • LED_STRIP_CHANNEL_MAPPING_BWRG = 177
  • LED_STRIP_CHANNEL_MAPPING_BWGR = 180
  • LED_STRIP_CHANNEL_MAPPING_WRBG = 201
  • LED_STRIP_CHANNEL_MAPPING_WRGB = 198
  • LED_STRIP_CHANNEL_MAPPING_WGBR = 216
  • LED_STRIP_CHANNEL_MAPPING_WGRB = 210
  • LED_STRIP_CHANNEL_MAPPING_WBGR = 228
  • LED_STRIP_CHANNEL_MAPPING_WBRG = 225

New in version 2.0.6 (Plugin).

Advanced Functions

int led_strip_get_api_version(LEDStrip *led_strip, uint8_t ret_api_version[3])

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.

int led_strip_get_response_expected(LEDStrip *led_strip, uint8_t function_id, bool *ret_response_expected)

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 led_strip_set_response_expected(). 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 led_strip_set_response_expected() for the list of function ID defines available for this function.

int led_strip_set_response_expected(LEDStrip *led_strip, uint8_t function_id, bool response_expected)

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 defines are available for this function:

  • LED_STRIP_FUNCTION_SET_RGB_VALUES = 1
  • LED_STRIP_FUNCTION_SET_FRAME_DURATION = 3
  • LED_STRIP_FUNCTION_SET_CLOCK_FREQUENCY = 7
  • LED_STRIP_FUNCTION_SET_CHIP_TYPE = 9
  • LED_STRIP_FUNCTION_SET_RGBW_VALUES = 11
  • LED_STRIP_FUNCTION_SET_CHANNEL_MAPPING = 13
  • LED_STRIP_FUNCTION_ENABLE_FRAME_RENDERED_CALLBACK = 15
  • LED_STRIP_FUNCTION_DISABLE_FRAME_RENDERED_CALLBACK = 16
int led_strip_set_response_expected_all(LEDStrip *led_strip, bool response_expected)

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

int led_strip_get_identity(LEDStrip *led_strip, char ret_uid[8], char ret_connected_uid[8], char *ret_position, uint8_t ret_hardware_version[3], uint8_t ret_firmware_version[3], uint16_t *ret_device_identifier)

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

void led_strip_register_callback(LEDStrip *led_strip, int16_t callback_id, void *function, void *user_data)

Registers the given function with the given callback_id. The user_data will be passed as the last parameter to the function.

The available callback IDs with corresponding function signatures are listed below.

int led_strip_enable_frame_rendered_callback(LEDStrip *led_strip)

Enables the LED_STRIP_CALLBACK_FRAME_RENDERED callback.

By default the callback is enabled.

New in version 2.0.6 (Plugin).

int led_strip_disable_frame_rendered_callback(LEDStrip *led_strip)

Disables the LED_STRIP_CALLBACK_FRAME_RENDERED callback.

By default the callback is enabled.

New in version 2.0.6 (Plugin).

int led_strip_is_frame_rendered_callback_enabled(LEDStrip *led_strip, bool *ret_enabled)

Returns true if the LED_STRIP_CALLBACK_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 led_strip_register_callback() function. The parameters consist of the device object, the callback ID, the callback function and optional user data:

void my_callback(int p, void *user_data) {
    printf("parameter: %d\n", p);
}

led_strip_register_callback(&led_strip, LED_STRIP_CALLBACK_EXAMPLE, (void *)my_callback, NULL);

The available constants with corresponding callback function signatures are described below.

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.

LED_STRIP_CALLBACK_FRAME_RENDERED
void callback(uint16_t length, void *user_data)

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

Constants

LED_STRIP_DEVICE_IDENTIFIER

This constant is used to identify a LED Strip Bricklet.

The led_strip_get_identity() function and the IPCON_CALLBACK_ENUMERATE callback of the IP Connection have a device_identifier parameter to specify the Brick's or Bricklet's type.

LED_STRIP_DEVICE_DISPLAY_NAME

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