C/C++ - Segment Display 4x7 Bricklet

This is the description of the C/C++ API bindings for the Segment Display 4x7 Bricklet. General information and technical specifications for the Segment Display 4x7 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_segment_display_4x7.h"

#define HOST "localhost"
#define PORT 4223
#define UID "XYZ" // Change XYZ to the UID of your Segment Display 4x7 Bricklet

const uint8_t digits[] = {0x3f,0x06,0x5b,0x4f,
                          0x66,0x6d,0x7d,0x07,
                          0x7f,0x6f,0x77,0x7c,
                          0x39,0x5e,0x79,0x71}; // 0~9,A,b,C,d,E,F

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

    // Create device object
    SegmentDisplay4x7 sd;
    segment_display_4x7_create(&sd, 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

    // Write "4223" to the display with full brightness without colon
    uint8_t segments[4] = {digits[4], digits[2], digits[2], digits[3]};
    segment_display_4x7_set_segments(&sd, segments, 7, false);

    printf("Press key to exit\n");
    getchar();
    segment_display_4x7_destroy(&sd);
    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 C/C++ 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
  • E_NON_ASCII_CHAR_IN_SECRET = -14

as defined in ip_connection.h.

All functions listed below are thread-safe.

Basic Functions

void segment_display_4x7_create(SegmentDisplay4x7 *segment_display_4x7, const char *uid, IPConnection *ipcon)
Parameters:
  • segment_display_4x7 – Type: SegmentDisplay4x7 *
  • uid – Type: const char *
  • ipcon – Type: IPConnection *

Creates the device object segment_display_4x7 with the unique device ID uid and adds it to the IPConnection ipcon:

SegmentDisplay4x7 segment_display_4x7;
segment_display_4x7_create(&segment_display_4x7, "YOUR_DEVICE_UID", &ipcon);

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

void segment_display_4x7_destroy(SegmentDisplay4x7 *segment_display_4x7)
Parameters:
  • segment_display_4x7 – Type: SegmentDisplay4x7 *

Removes the device object segment_display_4x7 from its IPConnection and destroys it. The device object cannot be used anymore afterwards.

int segment_display_4x7_set_segments(SegmentDisplay4x7 *segment_display_4x7, uint8_t segments[4], uint8_t brightness, bool colon)
Parameters:
  • segment_display_4x7 – Type: SegmentDisplay4x7 *
  • segments – Type: uint8_t[4], Range: [0 to 127]
  • brightness – Type: uint8_t, Range: [0 to 7]
  • colon – Type: bool
Returns:
  • error_code – Type: int

The 7-segment display can be set with bitmaps. Every bit controls one segment:

Bit order of one segment

For example to set a "5" you would want to activate segments 0, 2, 3, 5 and 6. This is represented by the number 0b01101101 = 0x6d = 109.

The brightness can be set between 0 (dark) and 7 (bright). The colon parameter turns the colon of the display on or off.

int segment_display_4x7_get_segments(SegmentDisplay4x7 *segment_display_4x7, uint8_t ret_segments[4], uint8_t *ret_brightness, bool *ret_colon)
Parameters:
  • segment_display_4x7 – Type: SegmentDisplay4x7 *
Output Parameters:
  • ret_segments – Type: uint8_t[4], Range: [0 to 127]
  • ret_brightness – Type: uint8_t, Range: [0 to 7]
  • ret_colon – Type: bool
Returns:
  • error_code – Type: int

Returns the segment, brightness and color data as set by segment_display_4x7_set_segments().

Advanced Functions

int segment_display_4x7_start_counter(SegmentDisplay4x7 *segment_display_4x7, int16_t value_from, int16_t value_to, int16_t increment, uint32_t length)
Parameters:
  • segment_display_4x7 – Type: SegmentDisplay4x7 *
  • value_from – Type: int16_t, Range: [-999 to 9999]
  • value_to – Type: int16_t, Range: [-999 to 9999]
  • increment – Type: int16_t, Range: [-999 to 9999]
  • length – Type: uint32_t, Unit: 1 ms, Range: [0 to 232 - 1]
Returns:
  • error_code – Type: int

Starts a counter with the from value that counts to the to value with the each step incremented by increment. length is the pause between each increment.

Example: If you set from to 0, to to 100, increment to 1 and length to 1000, a counter that goes from 0 to 100 with one second pause between each increment will be started.

Using a negative increment allows to count backwards.

You can stop the counter at every time by calling segment_display_4x7_set_segments().

int segment_display_4x7_get_counter_value(SegmentDisplay4x7 *segment_display_4x7, uint16_t *ret_value)
Parameters:
  • segment_display_4x7 – Type: SegmentDisplay4x7 *
Output Parameters:
  • ret_value – Type: uint16_t, Range: [-999 to 9999]
Returns:
  • error_code – Type: int

Returns the counter value that is currently shown on the display.

If there is no counter running a 0 will be returned.

int segment_display_4x7_get_identity(SegmentDisplay4x7 *segment_display_4x7, 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)
Parameters:
  • segment_display_4x7 – Type: SegmentDisplay4x7 *
Output Parameters:
  • ret_uid – Type: char[8]
  • ret_connected_uid – Type: char[8]
  • ret_position – Type: char, Range: ['a' to 'h', 'i', 'z']
  • ret_hardware_version – Type: uint8_t[3]
    • 0: major – Type: uint8_t, Range: [0 to 255]
    • 1: minor – Type: uint8_t, Range: [0 to 255]
    • 2: revision – Type: uint8_t, Range: [0 to 255]
  • ret_firmware_version – Type: uint8_t[3]
    • 0: major – Type: uint8_t, Range: [0 to 255]
    • 1: minor – Type: uint8_t, Range: [0 to 255]
    • 2: revision – Type: uint8_t, Range: [0 to 255]
  • ret_device_identifier – Type: uint16_t, Range: [0 to 216 - 1]
Returns:
  • error_code – Type: int

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', 'd', 'e', 'f', 'g' or 'h' (Bricklet Port). The Raspberry Pi HAT (Zero) Brick is always at position 'i' and the Bricklet connected to an Isolator Bricklet is always as position 'z'.

The device identifier numbers can be found here. There is also a constant for the device identifier of this Bricklet.

Callback Configuration Functions

void segment_display_4x7_register_callback(SegmentDisplay4x7 *segment_display_4x7, int16_t callback_id, void (*function)(void), void *user_data)
Parameters:
  • segment_display_4x7 – Type: SegmentDisplay4x7 *
  • callback_id – Type: int16_t
  • function – Type: void (*)(void)
  • user_data – Type: void *

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.

Callbacks

Callbacks can be registered to receive time critical or recurring data from the device. The registration is done with the segment_display_4x7_register_callback() function:

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

segment_display_4x7_register_callback(&segment_display_4x7,
                                      SEGMENT_DISPLAY_4X7_CALLBACK_EXAMPLE,
                                      (void (*)(void))my_callback,
                                      NULL);

The available constants with corresponding 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.

SEGMENT_DISPLAY_4X7_CALLBACK_COUNTER_FINISHED
void callback(void *user_data)
Callback Parameters:
  • user_data – Type: void *

This callback is triggered when the counter (see segment_display_4x7_start_counter()) is finished.

Virtual Functions

Virtual functions don't communicate with the device itself, but operate only on the API bindings device object. They can be called without the corresponding IP Connection object being connected.

int segment_display_4x7_get_api_version(SegmentDisplay4x7 *segment_display_4x7, uint8_t ret_api_version[3])
Parameters:
  • segment_display_4x7 – Type: SegmentDisplay4x7 *
Output Parameters:
  • ret_api_version – Type: uint8_t[3]
    • 0: major – Type: uint8_t, Range: [0 to 255]
    • 1: minor – Type: uint8_t, Range: [0 to 255]
    • 2: revision – Type: uint8_t, Range: [0 to 255]
Returns:
  • error_code – Type: int

Returns the version of the API definition 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 segment_display_4x7_get_response_expected(SegmentDisplay4x7 *segment_display_4x7, uint8_t function_id, bool *ret_response_expected)
Parameters:
  • segment_display_4x7 – Type: SegmentDisplay4x7 *
  • function_id – Type: uint8_t, Range: See constants
Output Parameters:
  • ret_response_expected – Type: bool
Returns:
  • error_code – Type: int

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 segment_display_4x7_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.

The following constants are available for this function:

For function_id:

  • SEGMENT_DISPLAY_4X7_FUNCTION_SET_SEGMENTS = 1
  • SEGMENT_DISPLAY_4X7_FUNCTION_START_COUNTER = 3
int segment_display_4x7_set_response_expected(SegmentDisplay4x7 *segment_display_4x7, uint8_t function_id, bool response_expected)
Parameters:
  • segment_display_4x7 – Type: SegmentDisplay4x7 *
  • function_id – Type: uint8_t, Range: See constants
  • response_expected – Type: bool
Returns:
  • error_code – Type: int

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 constants are available for this function:

For function_id:

  • SEGMENT_DISPLAY_4X7_FUNCTION_SET_SEGMENTS = 1
  • SEGMENT_DISPLAY_4X7_FUNCTION_START_COUNTER = 3
int segment_display_4x7_set_response_expected_all(SegmentDisplay4x7 *segment_display_4x7, bool response_expected)
Parameters:
  • segment_display_4x7 – Type: SegmentDisplay4x7 *
  • response_expected – Type: bool
Returns:
  • error_code – Type: int

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

Constants

SEGMENT_DISPLAY_4X7_DEVICE_IDENTIFIER

This constant is used to identify a Segment Display 4x7 Bricklet.

The segment_display_4x7_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.

SEGMENT_DISPLAY_4X7_DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Segment Display 4x7 Bricklet.