C/C++ - DMX Bricklet

This is the description of the C/C++ API bindings for the DMX Bricklet. General information and technical specifications for the DMX 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_dmx.h"

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

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

    // Create device object
    DMX dmx;
    dmx_create(&dmx, 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

    // Configure Bricklet as DMX master
    dmx_set_dmx_mode(&dmx, DMX_DMX_MODE_MASTER);

    // Write DMX frame with 3 channels
    dmx_write_frame(&dmx, (uint8_t[]){255, 128, 0}, 3);

    printf("Press key to exit\n");
    getchar();
    dmx_destroy(&dmx);
    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 call by reference. 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

as defined in ip_connection.h.

All functions listed below are thread-safe.

Basic Functions

void dmx_create(DMX *dmx, const char *uid, IPConnection *ipcon)

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

DMX dmx;
dmx_create(&dmx, "YOUR_DEVICE_UID", &ipcon);

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

void dmx_destroy(DMX *dmx)

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

int dmx_set_dmx_mode(DMX *dmx, uint8_t dmx_mode)

Sets the DMX mode to either master or slave.

Calling this function sets frame number to 0.

The default value is 0 (master).

The following defines are available for this function:

  • DMX_DMX_MODE_MASTER = 0
  • DMX_DMX_MODE_SLAVE = 1
int dmx_get_dmx_mode(DMX *dmx, uint8_t *ret_dmx_mode)

Returns the DMX mode, as set by dmx_set_dmx_mode().

The following defines are available for this function:

  • DMX_DMX_MODE_MASTER = 0
  • DMX_DMX_MODE_SLAVE = 1
int dmx_write_frame(DMX *dmx, uint8_t *frame, uint16_t frame_length)

Writes a DMX frame. The maximum frame size is 512 byte. Each byte represents one channel.

The next frame can be written after the DMX_CALLBACK_FRAME_STARTED callback was called. The frame is double buffered, so a new frame can be written as soon as the writing of the prior frame starts.

The data will be transfered when the next frame duration ends, see dmx_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 channels for first frame.
  • Wait for the DMX_CALLBACK_FRAME_STARTED callback.
  • Set channels for next frame.
  • Wait for the DMX_CALLBACK_FRAME_STARTED callback.
  • and so on.

This approach ensures that you can set new DMX data with a fixed frame rate.

This function can only be called in master mode.

int dmx_read_frame(DMX *dmx, uint8_t *ret_frame, uint16_t *ret_frame_length, uint32_t *ret_frame_number)

Returns the last frame that was written by the DMX master. The size of the array is equivalent to the number of channels in the frame. Each byte represents one channel.

The next frame is available after the DMX_CALLBACK_FRAME_AVAILABLE callback was called.

Generic approach:

Instead of polling this function you can also use the DMX_CALLBACK_FRAME callback. You can enable it with dmx_set_frame_callback_config().

The frame number starts at 0 and it is increased by one with each received frame.

This function can only be called in slave mode.

int dmx_set_frame_duration(DMX *dmx, uint16_t frame_duration)

Sets the duration of a frame in ms.

Example: If you want to achieve 20 frames per second, you should set the frame duration to 50ms (50ms * 20 = 1 second).

If you always want to send a frame as fast as possible you can set this value to 0.

This setting is only used in master mode.

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

int dmx_get_frame_duration(DMX *dmx, uint16_t *ret_frame_duration)

Returns the frame duration as set by dmx_set_frame_duration().

Advanced Functions

int dmx_get_frame_error_count(DMX *dmx, uint32_t *ret_overrun_error_count, uint32_t *ret_framing_error_count)

Returns the current number of overrun and framing errors.

int dmx_set_communication_led_config(DMX *dmx, uint8_t config)

Sets the communication LED configuration. By default the LED shows communication traffic, it flickers once for every 10 received data packets.

You can also turn the LED permanently on/off or show a heartbeat.

If the Bricklet is in bootloader mode, the LED is off.

The following defines are available for this function:

  • DMX_COMMUNICATION_LED_CONFIG_OFF = 0
  • DMX_COMMUNICATION_LED_CONFIG_ON = 1
  • DMX_COMMUNICATION_LED_CONFIG_SHOW_HEARTBEAT = 2
  • DMX_COMMUNICATION_LED_CONFIG_SHOW_COMMUNICATION = 3
int dmx_get_communication_led_config(DMX *dmx, uint8_t *ret_config)

Returns the configuration as set by dmx_set_communication_led_config()

The following defines are available for this function:

  • DMX_COMMUNICATION_LED_CONFIG_OFF = 0
  • DMX_COMMUNICATION_LED_CONFIG_ON = 1
  • DMX_COMMUNICATION_LED_CONFIG_SHOW_HEARTBEAT = 2
  • DMX_COMMUNICATION_LED_CONFIG_SHOW_COMMUNICATION = 3
int dmx_set_error_led_config(DMX *dmx, uint8_t config)

Sets the error LED configuration.

By default the error LED turns on if there is any error (see DMX_CALLBACK_FRAME_ERROR_COUNT callback). If you call this function with the Show-Error option again, the LED will turn off until the next error occurs.

You can also turn the LED permanently on/off or show a heartbeat.

If the Bricklet is in bootloader mode, the LED is off.

The following defines are available for this function:

  • DMX_ERROR_LED_CONFIG_OFF = 0
  • DMX_ERROR_LED_CONFIG_ON = 1
  • DMX_ERROR_LED_CONFIG_SHOW_HEARTBEAT = 2
  • DMX_ERROR_LED_CONFIG_SHOW_ERROR = 3
int dmx_get_error_led_config(DMX *dmx, uint8_t *ret_config)

Returns the configuration as set by dmx_set_error_led_config().

The following defines are available for this function:

  • DMX_ERROR_LED_CONFIG_OFF = 0
  • DMX_ERROR_LED_CONFIG_ON = 1
  • DMX_ERROR_LED_CONFIG_SHOW_HEARTBEAT = 2
  • DMX_ERROR_LED_CONFIG_SHOW_ERROR = 3
int dmx_get_api_version(DMX *dmx, 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 dmx_get_response_expected(DMX *dmx, 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 dmx_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 dmx_set_response_expected() for the list of function ID defines available for this function.

int dmx_set_response_expected(DMX *dmx, 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:

  • DMX_FUNCTION_SET_DMX_MODE = 1
  • DMX_FUNCTION_WRITE_FRAME = 3
  • DMX_FUNCTION_SET_FRAME_DURATION = 5
  • DMX_FUNCTION_SET_COMMUNICATION_LED_CONFIG = 8
  • DMX_FUNCTION_SET_ERROR_LED_CONFIG = 10
  • DMX_FUNCTION_SET_FRAME_CALLBACK_CONFIG = 12
  • DMX_FUNCTION_SET_WRITE_FIRMWARE_POINTER = 237
  • DMX_FUNCTION_SET_STATUS_LED_CONFIG = 239
  • DMX_FUNCTION_RESET = 243
  • DMX_FUNCTION_WRITE_UID = 248
int dmx_set_response_expected_all(DMX *dmx, bool response_expected)

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

int dmx_get_spitfp_error_count(DMX *dmx, uint32_t *ret_error_count_ack_checksum, uint32_t *ret_error_count_message_checksum, uint32_t *ret_error_count_frame, uint32_t *ret_error_count_overflow)

Returns the error count for the communication between Brick and Bricklet.

The errors are divided into

  • ACK checksum errors,
  • message checksum errors,
  • framing errors and
  • overflow errors.

The errors counts are for errors that occur on the Bricklet side. All Bricks have a similar function that returns the errors on the Brick side.

int dmx_set_bootloader_mode(DMX *dmx, uint8_t mode, uint8_t *ret_status)

Sets the bootloader mode and returns the status after the requested mode change was instigated.

You can change from bootloader mode to firmware mode and vice versa. A change from bootloader mode to firmware mode will only take place if the entry function, device identifier and CRC are present and correct.

This function is used by Brick Viewer during flashing. It should not be necessary to call it in a normal user program.

The following defines are available for this function:

  • DMX_BOOTLOADER_MODE_BOOTLOADER = 0
  • DMX_BOOTLOADER_MODE_FIRMWARE = 1
  • DMX_BOOTLOADER_MODE_BOOTLOADER_WAIT_FOR_REBOOT = 2
  • DMX_BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_REBOOT = 3
  • DMX_BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_ERASE_AND_REBOOT = 4
  • DMX_BOOTLOADER_STATUS_OK = 0
  • DMX_BOOTLOADER_STATUS_INVALID_MODE = 1
  • DMX_BOOTLOADER_STATUS_NO_CHANGE = 2
  • DMX_BOOTLOADER_STATUS_ENTRY_FUNCTION_NOT_PRESENT = 3
  • DMX_BOOTLOADER_STATUS_DEVICE_IDENTIFIER_INCORRECT = 4
  • DMX_BOOTLOADER_STATUS_CRC_MISMATCH = 5
int dmx_get_bootloader_mode(DMX *dmx, uint8_t *ret_mode)

Returns the current bootloader mode, see dmx_set_bootloader_mode().

The following defines are available for this function:

  • DMX_BOOTLOADER_MODE_BOOTLOADER = 0
  • DMX_BOOTLOADER_MODE_FIRMWARE = 1
  • DMX_BOOTLOADER_MODE_BOOTLOADER_WAIT_FOR_REBOOT = 2
  • DMX_BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_REBOOT = 3
  • DMX_BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_ERASE_AND_REBOOT = 4
int dmx_set_write_firmware_pointer(DMX *dmx, uint32_t pointer)

Sets the firmware pointer for dmx_write_firmware(). The pointer has to be increased by chunks of size 64. The data is written to flash every 4 chunks (which equals to one page of size 256).

This function is used by Brick Viewer during flashing. It should not be necessary to call it in a normal user program.

int dmx_write_firmware(DMX *dmx, uint8_t data[64], uint8_t *ret_status)

Writes 64 Bytes of firmware at the position as written by dmx_set_write_firmware_pointer() before. The firmware is written to flash every 4 chunks.

You can only write firmware in bootloader mode.

This function is used by Brick Viewer during flashing. It should not be necessary to call it in a normal user program.

int dmx_set_status_led_config(DMX *dmx, uint8_t config)

Sets the status LED configuration. By default the LED shows communication traffic between Brick and Bricklet, it flickers once for every 10 received data packets.

You can also turn the LED permanently on/off or show a heartbeat.

If the Bricklet is in bootloader mode, the LED is will show heartbeat by default.

The following defines are available for this function:

  • DMX_STATUS_LED_CONFIG_OFF = 0
  • DMX_STATUS_LED_CONFIG_ON = 1
  • DMX_STATUS_LED_CONFIG_SHOW_HEARTBEAT = 2
  • DMX_STATUS_LED_CONFIG_SHOW_STATUS = 3
int dmx_get_status_led_config(DMX *dmx, uint8_t *ret_config)

Returns the configuration as set by dmx_set_status_led_config()

The following defines are available for this function:

  • DMX_STATUS_LED_CONFIG_OFF = 0
  • DMX_STATUS_LED_CONFIG_ON = 1
  • DMX_STATUS_LED_CONFIG_SHOW_HEARTBEAT = 2
  • DMX_STATUS_LED_CONFIG_SHOW_STATUS = 3
int dmx_get_chip_temperature(DMX *dmx, int16_t *ret_temperature)

Returns the temperature in °C as measured inside the microcontroller. The value returned is not the ambient temperature!

The temperature is only proportional to the real temperature and it has bad accuracy. Practically it is only useful as an indicator for temperature changes.

int dmx_reset(DMX *dmx)

Calling this function will reset the Bricklet. All configurations will be lost.

After a reset you have to create new device objects, calling functions on the existing ones will result in undefined behavior!

int dmx_write_uid(DMX *dmx, uint32_t uid)

Writes a new UID into flash. If you want to set a new UID you have to decode the Base58 encoded UID string into an integer first.

We recommend that you use Brick Viewer to change the UID.

int dmx_read_uid(DMX *dmx, uint32_t *ret_uid)

Returns the current UID as an integer. Encode as Base58 to get the usual string version.

int dmx_get_identity(DMX *dmx, 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 dmx_register_callback(DMX *dmx, 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 dmx_set_frame_callback_config(DMX *dmx, bool frame_started_callback_enabled, bool frame_available_callback_enabled, bool frame_callback_enabled, bool frame_error_count_callback_enabled)

Enables/Disables the different callbacks. By default the DMX_CALLBACK_FRAME_STARTED callback and DMX_CALLBACK_FRAME_AVAILABLE callback are enabled while the DMX_CALLBACK_FRAME callback and DMX_CALLBACK_FRAME_ERROR_COUNT callback are disabled.

If you want to use the DMX_CALLBACK_FRAME callback you can enable it and disable the cb:Frame Available callback at the same time. It becomes redundant in this case.

int dmx_get_frame_callback_config(DMX *dmx, bool *ret_frame_started_callback_enabled, bool *ret_frame_available_callback_enabled, bool *ret_frame_callback_enabled, bool *ret_frame_error_count_callback_enabled)

Returns the frame callback config as set by dmx_set_frame_callback_config().

Callbacks

Callbacks can be registered to receive time critical or recurring data from the device. The registration is done with the dmx_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);
}

dmx_register_callback(&dmx, DMX_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.

DMX_CALLBACK_FRAME_STARTED
void callback(void *user_data)

This callback is triggered as soon as a new frame write is started. You should send the data for the next frame directly after this callback was triggered.

For an explanation of the general approach see dmx_write_frame().

This callback can be enabled via dmx_set_frame_callback_config().

This callback can only be triggered in master mode.

DMX_CALLBACK_FRAME_AVAILABLE
void callback(uint32_t frame_number, void *user_data)

This callback is triggered in slave mode when a new frame was received from the DMX master and it can be read out. You have to read the frame before the master has written the next frame, see dmx_read_frame() for more details.

The parameter is the frame number, it is increased by one with each received frame.

This callback can be enabled via dmx_set_frame_callback_config().

This callback can only be triggered in slave mode.

DMX_CALLBACK_FRAME
void callback(uint8_t *frame, uint16_t frame_length, uint32_t frame_number, void *user_data)

This callback is called as soon as a new frame is available (written by the DMX master).

The size of the array is equivalent to the number of channels in the frame. Each byte represents one channel.

This callback can be enabled via dmx_set_frame_callback_config().

This callback can only be triggered in slave mode.

DMX_CALLBACK_FRAME_ERROR_COUNT
void callback(uint32_t overrun_error_count, uint32_t framing_error_count, void *user_data)

This callback is called if a new error occurs. It returns the current overrun and framing error count.

Constants

DMX_DEVICE_IDENTIFIER

This constant is used to identify a DMX Bricklet.

The dmx_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.

DMX_DEVICE_DISPLAY_NAME

This constant represents the human readable name of a DMX Bricklet.