C/C++ - Rotary Encoder Bricklet

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

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

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

    // Create device object
    RotaryEncoder re;
    rotary_encoder_create(&re, 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 count without reset
    int32_t count;
    if(rotary_encoder_get_count(&re, false, &count) < 0) {
        fprintf(stderr, "Could not get count without reset, probably timeout\n");
        return 1;
    }

    printf("Count: %d\n", count);

    printf("Press key to exit\n");
    getchar();
    rotary_encoder_destroy(&re);
    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_rotary_encoder.h"

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

// Callback function for count callback
void cb_count(int32_t count, void *user_data) {
    (void)user_data; // avoid unused parameter warning

    printf("Count: %d\n", count);
}

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

    // Create device object
    RotaryEncoder re;
    rotary_encoder_create(&re, 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 count callback to function cb_count
    rotary_encoder_register_callback(&re,
                                     ROTARY_ENCODER_CALLBACK_COUNT,
                                     (void (*)(void))cb_count,
                                     NULL);

    // Set period for count callback to 0.05s (50ms)
    // Note: The count callback is only called every 0.05 seconds
    //       if the count has changed since the last call!
    rotary_encoder_set_count_callback_period(&re, 50);

    printf("Press key to exit\n");
    getchar();
    rotary_encoder_destroy(&re);
    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
  • E_WRONG_DEVICE_TYPE = -15
  • E_DEVICE_REPLACED = -16
  • E_WRONG_RESPONSE_LENGTH = -17

as defined in ip_connection.h.

All functions listed below are thread-safe.

Basic Functions

void rotary_encoder_create(RotaryEncoder *rotary_encoder, const char *uid, IPConnection *ipcon)
Parameters:
  • rotary_encoder – Type: RotaryEncoder *
  • uid – Type: const char *
  • ipcon – Type: IPConnection *

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

RotaryEncoder rotary_encoder;
rotary_encoder_create(&rotary_encoder, "YOUR_DEVICE_UID", &ipcon);

This device object can be used after the IP connection has been connected.

void rotary_encoder_destroy(RotaryEncoder *rotary_encoder)
Parameters:
  • rotary_encoder – Type: RotaryEncoder *

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

int rotary_encoder_get_count(RotaryEncoder *rotary_encoder, bool reset, int32_t *ret_count)
Parameters:
  • rotary_encoder – Type: RotaryEncoder *
  • reset – Type: bool
Output Parameters:
  • ret_count – Type: int32_t, Range: [-231 to 231 - 1]
Returns:
  • error_code – Type: int

Returns the current count of the encoder. If you set reset to true, the count is set back to 0 directly after the current count is read.

The encoder has 24 steps per rotation

Turning the encoder to the left decrements the counter, so a negative count is possible.

int rotary_encoder_is_pressed(RotaryEncoder *rotary_encoder, bool *ret_pressed)
Parameters:
  • rotary_encoder – Type: RotaryEncoder *
Output Parameters:
  • ret_pressed – Type: bool
Returns:
  • error_code – Type: int

Returns true if the button is pressed and false otherwise.

It is recommended to use the ROTARY_ENCODER_CALLBACK_PRESSED and ROTARY_ENCODER_CALLBACK_RELEASED callbacks to handle the button.

Advanced Functions

int rotary_encoder_get_identity(RotaryEncoder *rotary_encoder, 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:
  • rotary_encoder – Type: RotaryEncoder *
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 rotary_encoder_register_callback(RotaryEncoder *rotary_encoder, int16_t callback_id, void (*function)(void), void *user_data)
Parameters:
  • rotary_encoder – Type: RotaryEncoder *
  • 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.

int rotary_encoder_set_count_callback_period(RotaryEncoder *rotary_encoder, uint32_t period)
Parameters:
  • rotary_encoder – Type: RotaryEncoder *
  • period – Type: uint32_t, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0
Returns:
  • error_code – Type: int

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

The ROTARY_ENCODER_CALLBACK_COUNT callback is only triggered if the count has changed since the last triggering.

int rotary_encoder_get_count_callback_period(RotaryEncoder *rotary_encoder, uint32_t *ret_period)
Parameters:
  • rotary_encoder – Type: RotaryEncoder *
Output Parameters:
  • ret_period – Type: uint32_t, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0
Returns:
  • error_code – Type: int

Returns the period as set by rotary_encoder_set_count_callback_period().

int rotary_encoder_set_count_callback_threshold(RotaryEncoder *rotary_encoder, char option, int32_t min, int32_t max)
Parameters:
  • rotary_encoder – Type: RotaryEncoder *
  • option – Type: char, Range: See constants, Default: 'x'
  • min – Type: int32_t, Range: [-231 to 231 - 1], Default: 0
  • max – Type: int32_t, Range: [-231 to 231 - 1], Default: 0
Returns:
  • error_code – Type: int

Sets the thresholds for the ROTARY_ENCODER_CALLBACK_COUNT_REACHED callback.

The following options are possible:

Option Description
'x' Callback is turned off
'o' Callback is triggered when the count is outside the min and max values
'i' Callback is triggered when the count is inside the min and max values
'<' Callback is triggered when the count is smaller than the min value (max is ignored)
'>' Callback is triggered when the count is greater than the min value (max is ignored)

The following constants are available for this function:

For option:

  • ROTARY_ENCODER_THRESHOLD_OPTION_OFF = 'x'
  • ROTARY_ENCODER_THRESHOLD_OPTION_OUTSIDE = 'o'
  • ROTARY_ENCODER_THRESHOLD_OPTION_INSIDE = 'i'
  • ROTARY_ENCODER_THRESHOLD_OPTION_SMALLER = '<'
  • ROTARY_ENCODER_THRESHOLD_OPTION_GREATER = '>'
int rotary_encoder_get_count_callback_threshold(RotaryEncoder *rotary_encoder, char *ret_option, int32_t *ret_min, int32_t *ret_max)
Parameters:
  • rotary_encoder – Type: RotaryEncoder *
Output Parameters:
  • ret_option – Type: char, Range: See constants, Default: 'x'
  • ret_min – Type: int32_t, Range: [-231 to 231 - 1], Default: 0
  • ret_max – Type: int32_t, Range: [-231 to 231 - 1], Default: 0
Returns:
  • error_code – Type: int

Returns the threshold as set by rotary_encoder_set_count_callback_threshold().

The following constants are available for this function:

For ret_option:

  • ROTARY_ENCODER_THRESHOLD_OPTION_OFF = 'x'
  • ROTARY_ENCODER_THRESHOLD_OPTION_OUTSIDE = 'o'
  • ROTARY_ENCODER_THRESHOLD_OPTION_INSIDE = 'i'
  • ROTARY_ENCODER_THRESHOLD_OPTION_SMALLER = '<'
  • ROTARY_ENCODER_THRESHOLD_OPTION_GREATER = '>'
int rotary_encoder_set_debounce_period(RotaryEncoder *rotary_encoder, uint32_t debounce)
Parameters:
  • rotary_encoder – Type: RotaryEncoder *
  • debounce – Type: uint32_t, Unit: 1 ms, Range: [0 to 232 - 1], Default: 100
Returns:
  • error_code – Type: int

Sets the period with which the threshold callback

is triggered, if the thresholds

keeps being reached.

int rotary_encoder_get_debounce_period(RotaryEncoder *rotary_encoder, uint32_t *ret_debounce)
Parameters:
  • rotary_encoder – Type: RotaryEncoder *
Output Parameters:
  • ret_debounce – Type: uint32_t, Unit: 1 ms, Range: [0 to 232 - 1], Default: 100
Returns:
  • error_code – Type: int

Returns the debounce period as set by rotary_encoder_set_debounce_period().

Callbacks

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

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

rotary_encoder_register_callback(&rotary_encoder,
                                 ROTARY_ENCODER_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.

ROTARY_ENCODER_CALLBACK_COUNT
void callback(int32_t count, void *user_data)
Callback Parameters:
  • count – Type: int32_t, Range: [-231 to 231 - 1]
  • user_data – Type: void *

This callback is triggered periodically with the period that is set by rotary_encoder_set_count_callback_period(). The parameter is the count of the encoder.

The ROTARY_ENCODER_CALLBACK_COUNT callback is only triggered if the count has changed since the last triggering.

ROTARY_ENCODER_CALLBACK_COUNT_REACHED
void callback(int32_t count, void *user_data)
Callback Parameters:
  • count – Type: int32_t, Range: [-231 to 231 - 1]
  • user_data – Type: void *

This callback is triggered when the threshold as set by rotary_encoder_set_count_callback_threshold() is reached. The parameter is the count of the encoder.

If the threshold keeps being reached, the callback is triggered periodically with the period as set by rotary_encoder_set_debounce_period().

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

This callback is triggered when the button is pressed.

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

This callback is triggered when the button is released.

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 rotary_encoder_get_api_version(RotaryEncoder *rotary_encoder, uint8_t ret_api_version[3])
Parameters:
  • rotary_encoder – Type: RotaryEncoder *
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 rotary_encoder_get_response_expected(RotaryEncoder *rotary_encoder, uint8_t function_id, bool *ret_response_expected)
Parameters:
  • rotary_encoder – Type: RotaryEncoder *
  • 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 rotary_encoder_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 sent and errors are silently ignored, because they cannot be detected.

The following constants are available for this function:

For function_id:

  • ROTARY_ENCODER_FUNCTION_SET_COUNT_CALLBACK_PERIOD = 2
  • ROTARY_ENCODER_FUNCTION_SET_COUNT_CALLBACK_THRESHOLD = 4
  • ROTARY_ENCODER_FUNCTION_SET_DEBOUNCE_PERIOD = 6
int rotary_encoder_set_response_expected(RotaryEncoder *rotary_encoder, uint8_t function_id, bool response_expected)
Parameters:
  • rotary_encoder – Type: RotaryEncoder *
  • 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 sent and errors are silently ignored, because they cannot be detected.

The following constants are available for this function:

For function_id:

  • ROTARY_ENCODER_FUNCTION_SET_COUNT_CALLBACK_PERIOD = 2
  • ROTARY_ENCODER_FUNCTION_SET_COUNT_CALLBACK_THRESHOLD = 4
  • ROTARY_ENCODER_FUNCTION_SET_DEBOUNCE_PERIOD = 6
int rotary_encoder_set_response_expected_all(RotaryEncoder *rotary_encoder, bool response_expected)
Parameters:
  • rotary_encoder – Type: RotaryEncoder *
  • 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

ROTARY_ENCODER_DEVICE_IDENTIFIER

This constant is used to identify a Rotary Encoder Bricklet.

The rotary_encoder_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.

ROTARY_ENCODER_DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Rotary Encoder Bricklet.