C/C++ - Real-Time Clock Bricklet

This is the description of the C/C++ API bindings for the Real-Time Clock Bricklet. General information and technical specifications for the Real-Time Clock 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)

 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
#define __STDC_FORMAT_MACROS // for PRId64/PRIu64 in C++

#include <stdio.h>
#include <inttypes.h>

#include "ip_connection.h"
#include "bricklet_real_time_clock.h"

#define HOST "localhost"
#define PORT 4223
#define UID "XYZ" // Change XYZ to the UID of your Real-Time Clock Bricklet

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

    // Create device object
    RealTimeClock rtc;
    real_time_clock_create(&rtc, 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

    // Get current date and time
    uint16_t year; uint8_t month, day, hour, minute, second, centisecond, weekday;
    if(real_time_clock_get_date_time(&rtc, &year, &month, &day, &hour, &minute, &second,
                                     &centisecond, &weekday) < 0) {
        fprintf(stderr, "Could not get date and time, probably timeout\n");
        return 1;
    }

    printf("Year: %u\n", year);
    printf("Month: %u\n", month);
    printf("Day: %u\n", day);
    printf("Hour: %u\n", hour);
    printf("Minute: %u\n", minute);
    printf("Second: %u\n", second);
    printf("Centisecond: %u\n", centisecond);
    printf("Weekday: %u\n", weekday);

    // Get current timestamp
    int64_t timestamp;
    if(real_time_clock_get_timestamp(&rtc, &timestamp) < 0) {
        fprintf(stderr, "Could not get timestamp, probably timeout\n");
        return 1;
    }

    printf("Timestamp: %" PRId64 " ms\n", timestamp);

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

Callback

Download (example_callback.c)

 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
#define __STDC_FORMAT_MACROS // for PRId64/PRIu64 in C++

#include <stdio.h>
#include <inttypes.h>

#include "ip_connection.h"
#include "bricklet_real_time_clock.h"

#define HOST "localhost"
#define PORT 4223
#define UID "XYZ" // Change XYZ to the UID of your Real-Time Clock Bricklet

// Callback function for date and time callback
void cb_date_time(uint16_t year, uint8_t month, uint8_t day, uint8_t hour, uint8_t minute,
                  uint8_t second, uint8_t centisecond, uint8_t weekday, int64_t timestamp,
                  void *user_data) {
    (void)user_data; // avoid unused parameter warning

    printf("Year: %u\n", year);
    printf("Month: %u\n", month);
    printf("Day: %u\n", day);
    printf("Hour: %u\n", hour);
    printf("Minute: %u\n", minute);
    printf("Second: %u\n", second);
    printf("Centisecond: %u\n", centisecond);
    printf("Weekday: %u\n", weekday);
    printf("Timestamp: %" PRId64 "\n", timestamp);
    printf("\n");
}

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

    // Create device object
    RealTimeClock rtc;
    real_time_clock_create(&rtc, 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

    // Register date and time callback to function cb_date_time
    real_time_clock_register_callback(&rtc,
                                      REAL_TIME_CLOCK_CALLBACK_DATE_TIME,
                                      (void *)cb_date_time,
                                      NULL);

    // Set period for date and time callback to 5s (5000ms)
    // Note: The date and time callback is only called every 5 seconds
    //       if the date and time has changed since the last call!
    real_time_clock_set_date_time_callback_period(&rtc, 5000);

    printf("Press key to exit\n");
    getchar();
    real_time_clock_destroy(&rtc);
    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 real_time_clock_create(RealTimeClock *real_time_clock, const char *uid, IPConnection *ipcon)

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

RealTimeClock real_time_clock;
real_time_clock_create(&real_time_clock, "YOUR_DEVICE_UID", &ipcon);

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

void real_time_clock_destroy(RealTimeClock *real_time_clock)

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

int real_time_clock_set_date_time(RealTimeClock *real_time_clock, uint16_t year, uint8_t month, uint8_t day, uint8_t hour, uint8_t minute, uint8_t second, uint8_t centisecond, uint8_t weekday)

Sets the current date (including weekday) and the current time with hundredths of a second resolution.

Possible value ranges:

  • Year: 2000 to 2099
  • Month: 1 to 12 (January to December)
  • Day: 1 to 31
  • Hour: 0 to 23
  • Minute: 0 to 59
  • Second: 0 to 59
  • Centisecond: 0 to 99
  • Weekday: 1 to 7 (Monday to Sunday)

If the backup battery is installed then the real-time clock keeps date and time even if the Bricklet is not powered by a Brick.

The real-time clock handles leap year and inserts the 29th of February accordingly. But leap seconds, time zones and daylight saving time are not handled.

The following defines are available for this function:

  • REAL_TIME_CLOCK_WEEKDAY_MONDAY = 1
  • REAL_TIME_CLOCK_WEEKDAY_TUESDAY = 2
  • REAL_TIME_CLOCK_WEEKDAY_WEDNESDAY = 3
  • REAL_TIME_CLOCK_WEEKDAY_THURSDAY = 4
  • REAL_TIME_CLOCK_WEEKDAY_FRIDAY = 5
  • REAL_TIME_CLOCK_WEEKDAY_SATURDAY = 6
  • REAL_TIME_CLOCK_WEEKDAY_SUNDAY = 7
int real_time_clock_get_date_time(RealTimeClock *real_time_clock, uint16_t *ret_year, uint8_t *ret_month, uint8_t *ret_day, uint8_t *ret_hour, uint8_t *ret_minute, uint8_t *ret_second, uint8_t *ret_centisecond, uint8_t *ret_weekday)

Returns the current date (including weekday) and the current time of the real-time clock with hundredths of a second resolution.

The following defines are available for this function:

  • REAL_TIME_CLOCK_WEEKDAY_MONDAY = 1
  • REAL_TIME_CLOCK_WEEKDAY_TUESDAY = 2
  • REAL_TIME_CLOCK_WEEKDAY_WEDNESDAY = 3
  • REAL_TIME_CLOCK_WEEKDAY_THURSDAY = 4
  • REAL_TIME_CLOCK_WEEKDAY_FRIDAY = 5
  • REAL_TIME_CLOCK_WEEKDAY_SATURDAY = 6
  • REAL_TIME_CLOCK_WEEKDAY_SUNDAY = 7
int real_time_clock_get_timestamp(RealTimeClock *real_time_clock, int64_t *ret_timestamp)

Returns the current date and the time of the real-time clock converted to milliseconds. The timestamp has an effective resolution of hundredths of a second.

Advanced Functions

int real_time_clock_set_offset(RealTimeClock *real_time_clock, int8_t offset)

Sets the offset the real-time clock should compensate for in 2.17 ppm steps between -277.76 ppm (-128) and +275.59 ppm (127).

The real-time clock time can deviate from the actual time due to the frequency deviation of its 32.768 kHz crystal. Even without compensation (factory default) the resulting time deviation should be at most ±20 ppm (±52.6 seconds per month).

This deviation can be calculated by comparing the same duration measured by the real-time clock (rtc_duration) an accurate reference clock (ref_duration).

For best results the configured offset should be set to 0 ppm first and then a duration of at least 6 hours should be measured.

The new offset (new_offset) can be calculated from the currently configured offset (current_offset) and the measured durations as follow:

new_offset = current_offset - round(1000000 * (rtc_duration - ref_duration) / rtc_duration / 2.17)

If you want to calculate the offset, then we recommend using the calibration dialog in Brick Viewer, instead of doing it manually.

The offset is saved in the EEPROM of the Bricklet and only needs to be configured once.

int real_time_clock_get_offset(RealTimeClock *real_time_clock, int8_t *ret_offset)

Returns the offset as set by real_time_clock_set_offset().

int real_time_clock_get_api_version(RealTimeClock *real_time_clock, 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 real_time_clock_get_response_expected(RealTimeClock *real_time_clock, 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 real_time_clock_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 real_time_clock_set_response_expected() for the list of function ID defines available for this function.

int real_time_clock_set_response_expected(RealTimeClock *real_time_clock, 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:

  • REAL_TIME_CLOCK_FUNCTION_SET_DATE_TIME = 1
  • REAL_TIME_CLOCK_FUNCTION_SET_OFFSET = 4
  • REAL_TIME_CLOCK_FUNCTION_SET_DATE_TIME_CALLBACK_PERIOD = 6
  • REAL_TIME_CLOCK_FUNCTION_SET_ALARM = 8
int real_time_clock_set_response_expected_all(RealTimeClock *real_time_clock, bool response_expected)

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

int real_time_clock_get_identity(RealTimeClock *real_time_clock, 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 real_time_clock_register_callback(RealTimeClock *real_time_clock, 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 real_time_clock_set_date_time_callback_period(RealTimeClock *real_time_clock, uint32_t period)

Sets the period in ms with which the REAL_TIME_CLOCK_CALLBACK_DATE_TIME callback is triggered periodically. A value of 0 turns the callback off.

The REAL_TIME_CLOCK_CALLBACK_DATE_TIME Callback is only triggered if the date or time changed since the last triggering.

The default value is 0.

New in version 2.0.1 (Plugin).

int real_time_clock_get_date_time_callback_period(RealTimeClock *real_time_clock, uint32_t *ret_period)

Returns the period as set by real_time_clock_set_date_time_callback_period().

New in version 2.0.1 (Plugin).

int real_time_clock_set_alarm(RealTimeClock *real_time_clock, int8_t month, int8_t day, int8_t hour, int8_t minute, int8_t second, int8_t weekday, int32_t interval)

Configures a repeatable alarm. The REAL_TIME_CLOCK_CALLBACK_ALARM callback is triggered if the current date and time matches the configured alarm.

Setting a parameter to -1 means that it should be disabled and doesn't take part in the match. Setting all parameters to -1 disables the alarm completely.

For example, to make the alarm trigger every day at 7:30 AM it can be configured as (-1, -1, 7, 30, -1, -1, -1). The hour is set to match 7 and the minute is set to match 30. The alarm is triggered if all enabled parameters match.

The interval has a special role. It allows to make the alarm reconfigure itself. This is useful if you need a repeated alarm that cannot be expressed by matching the current date and time. For example, to make the alarm trigger every 23 seconds it can be configured as (-1, -1, -1, -1, -1, -1, 23). Internally the Bricklet will take the current date and time, add 23 seconds to it and set the result as its alarm. The first alarm will be triggered 23 seconds after the call. Because the interval is not -1, the Bricklet will do the same again internally, take the current date and time, add 23 seconds to it and set that as its alarm. This results in a repeated alarm that triggers every 23 seconds.

The interval can also be used in combination with the other parameters. For example, configuring the alarm as (-1, -1, 7, 30, -1, -1, 300) results in an alarm that triggers every day at 7:30 AM and is then repeated every 5 minutes.

The following defines are available for this function:

  • REAL_TIME_CLOCK_ALARM_MATCH_DISABLED = -1
  • REAL_TIME_CLOCK_ALARM_INTERVAL_DISABLED = -1

New in version 2.0.1 (Plugin).

int real_time_clock_get_alarm(RealTimeClock *real_time_clock, int8_t *ret_month, int8_t *ret_day, int8_t *ret_hour, int8_t *ret_minute, int8_t *ret_second, int8_t *ret_weekday, int32_t *ret_interval)

Returns the alarm configuration as set by real_time_clock_set_alarm().

The following defines are available for this function:

  • REAL_TIME_CLOCK_ALARM_MATCH_DISABLED = -1
  • REAL_TIME_CLOCK_ALARM_INTERVAL_DISABLED = -1

New in version 2.0.1 (Plugin).

Callbacks

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

real_time_clock_register_callback(&real_time_clock, REAL_TIME_CLOCK_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.

REAL_TIME_CLOCK_CALLBACK_DATE_TIME
void callback(uint16_t year, uint8_t month, uint8_t day, uint8_t hour, uint8_t minute, uint8_t second, uint8_t centisecond, uint8_t weekday, int64_t timestamp, void *user_data)

This callback is triggered periodically with the period that is set by real_time_clock_set_date_time_callback_period(). The parameters are the same as for real_time_clock_get_date_time() and real_time_clock_get_timestamp() combined.

The REAL_TIME_CLOCK_CALLBACK_DATE_TIME callback is only triggered if the date or time changed since the last triggering.

The following defines are available for this function:

  • REAL_TIME_CLOCK_WEEKDAY_MONDAY = 1
  • REAL_TIME_CLOCK_WEEKDAY_TUESDAY = 2
  • REAL_TIME_CLOCK_WEEKDAY_WEDNESDAY = 3
  • REAL_TIME_CLOCK_WEEKDAY_THURSDAY = 4
  • REAL_TIME_CLOCK_WEEKDAY_FRIDAY = 5
  • REAL_TIME_CLOCK_WEEKDAY_SATURDAY = 6
  • REAL_TIME_CLOCK_WEEKDAY_SUNDAY = 7

New in version 2.0.1 (Plugin).

REAL_TIME_CLOCK_CALLBACK_ALARM
void callback(uint16_t year, uint8_t month, uint8_t day, uint8_t hour, uint8_t minute, uint8_t second, uint8_t centisecond, uint8_t weekday, int64_t timestamp, void *user_data)

This callback is triggered every time the current date and time matches the configured alarm (see real_time_clock_set_alarm()). The parameters are the same as for real_time_clock_get_date_time() and real_time_clock_get_timestamp() combined.

The following defines are available for this function:

  • REAL_TIME_CLOCK_WEEKDAY_MONDAY = 1
  • REAL_TIME_CLOCK_WEEKDAY_TUESDAY = 2
  • REAL_TIME_CLOCK_WEEKDAY_WEDNESDAY = 3
  • REAL_TIME_CLOCK_WEEKDAY_THURSDAY = 4
  • REAL_TIME_CLOCK_WEEKDAY_FRIDAY = 5
  • REAL_TIME_CLOCK_WEEKDAY_SATURDAY = 6
  • REAL_TIME_CLOCK_WEEKDAY_SUNDAY = 7

New in version 2.0.1 (Plugin).

Constants

REAL_TIME_CLOCK_DEVICE_IDENTIFIER

This constant is used to identify a Real-Time Clock Bricklet.

The real_time_clock_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.

REAL_TIME_CLOCK_DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Real-Time Clock Bricklet.