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.
The example code below is Public Domain (CC0 1.0).
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 | #include <stdio.h>
#include "ip_connection.h"
#include "bricklet_led_strip.h"
#define HOST "localhost"
#define PORT 4223
#define UID "XYZ" // Change to your UID
int main() {
// Create IP connection
IPConnection ipcon;
ipcon_create(&ipcon);
// Create device object
LEDStrip led_strip;
led_strip_create(&led_strip, UID, &ipcon);
// Connect to brickd
if(ipcon_connect(&ipcon, HOST, PORT) < 0) {
fprintf(stderr, "Could not connect\n");
exit(1);
}
// Don't use device before ipcon is connected
// Set first 10 LEDs to green
uint8_t r[16] = {0};
uint8_t g[16] = {255, 255, 255, 255, 255, 255, 255, 255, 255, 255};
uint8_t b[16] = {0};
led_strip_set_rgb_values(&led_strip, 0, 10, r, g, b);
printf("Press key to exit\n");
getchar();
ipcon_destroy(&ipcon); // Calls ipcon_disconnect internally
}
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 | #include <stdio.h>
#include "ip_connection.h"
#include "bricklet_led_strip.h"
#define HOST "localhost"
#define PORT 4223
#define UID "XYZ" // Change to your UID
#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;
// Frame rendered callback, is called when a new frame was rendered
// We increase the index of one blue LED with every frame
void cb_frame_rendered(uint16_t length, void *user_data) {
(void)length; // avoid unused parameter warning
LEDStrip *led_strip = (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(led_strip, 0, NUM_LEDS, r, g, b);
}
int main() {
// Create IP connection
IPConnection ipcon;
ipcon_create(&ipcon);
// Create device object
LEDStrip led_strip;
led_strip_create(&led_strip, UID, &ipcon);
// Connect to brickd
if(ipcon_connect(&ipcon, HOST, PORT) < 0) {
fprintf(stderr, "Could not connect\n");
exit(1);
}
// Don't use device before ipcon is connected
// Set frame duration to 50ms (20 frames per second)
led_strip_set_frame_duration(&led_strip, 50);
// Register frame rendered callback to function cb_frame_rendered
led_strip_register_callback(&led_strip,
LED_STRIP_CALLBACK_FRAME_RENDERED,
(void *)cb_frame_rendered,
(void *)&led_strip);
// Set initial rgb values to get started
led_strip_set_rgb_values(&led_strip, 0, NUM_LEDS, r, g, b);
printf("Press key to exit\n");
getchar();
ipcon_destroy(&ipcon); // Calls ipcon_disconnect internally
}
|
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 call by reference. These parameters are labeled with the ret_ prefix.
Possible error codes are:
as defined in ip_connection.h.
All functions listed below are thread-safe.
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).
Removes the device object led_strip from its IPConnection and destroys it. The device object cannot be used anymore afterwards.
Sets the rgb values for the LEDs with the given length starting from index.
The maximum length is 16, the index goes from 0 to 319 and the rgb values have 8 bits each.
Example: If you set
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.
Returns the rgb with the given length starting from the given index.
The values are the last values that were set by led_strip_set_rgb_values().
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).
Returns the frame duration as set by led_strip_set_frame_duration().
Returns the current supply voltage of the LEDs. The voltage is given in mV.
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).
Returns the currently used clock frequency as set by led_strip_set_clock_frequency().
New in version 2.0.1 (Plugin).
Sets the type of the led driver chip. We currently support the chips
The WS2812 is sometimes also called "NeoPixel", a name coined by Adafruit.
The default value is WS2801 (chip = 2801).
The following defines are available for this function:
New in version 2.0.2 (Plugin).
Returns the currently used chip type as set by led_strip_set_chip_type().
The following defines are available for this function:
New in version 2.0.2 (Plugin).
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.
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.
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 and callbacks it is always disabled.
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:
Changes the response expected flag for all setter and callback configuration functions of this device at once.
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.
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.
void callback(uint16_t length, void *user_data)
This callback is triggered directly after a new frame is rendered.
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().
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.