C/C++ - Accelerometer Bricklet – Tinkerforge

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# C/C++ - Accelerometer Bricklet

Note

This Bricklet is currently in the prototype stage and the software/hardware as well as the documentation is in an incomplete state.

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

    #define HOST "localhost"
    #define PORT 4223
    #define UID "sad" // Change to your UID

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

        // Create device object
        Accelerometer acc;
        accelerometer_create(&acc, 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

        // Get current acceleration
        int16_t x; int16_t y; int16_t z;
        if(accelerometer_get_acceleration(&acc, &x, &y, &z) < 0) {
            fprintf(stderr, "Could not get value, probably timeout\n");
            exit(1);
        }

        printf("Acceleration(X): %fG\n", x/1000.0);
        printf("Acceleration(Y): %fG\n", y/1000.0);
        printf("Acceleration(Z): %fG\n", z/1000.0);
        printf("\n");

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

### Callback

Download (example_callback.c)

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    #include <stdio.h>

    #include "ip_connection.h"
    #include "bricklet_accelerometer.h"

    #define HOST "localhost"
    #define PORT 4223
    #define UID "sad" // Change to your UID

    // Callback for acceleration
    void cb_acceleration(int16_t x, int16_t y, int16_t z, void *user_data) {
        (void)user_data; // avoid unused parameter warning

        printf("Acceleration(X): %fG\n", x/1000.0);
        printf("Acceleration(Y): %fG\n", y/1000.0);
        printf("Acceleration(Z): %fG\n", z/1000.0);
        printf("\n");
    }

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

        // Create device object
        Accelerometer acc;
        accelerometer_create(&acc, 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 Period for acceleration callback to 1s (1000ms)
        // Note: The callback is only called every second if the
        //       acceleration has changed since the last call!
        accelerometer_set_acceleration_callback_period(&acc, 1000);

        // Register color callback to function cb_acceleration
        accelerometer_register_callback(&acc,
                                        ACCELEROMETER_CALLBACK_ACCELERATION,
                                        (void *)cb_acceleration/1000.0,
                                        NULL);

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

### Threshold

Download (example_threshold.c)

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    #include <stdio.h>

    #include "ip_connection.h"
    #include "bricklet_accelerometer.h"

    #define HOST "localhost"
    #define PORT 4223
    #define UID "sad" // Change to your UID

    // Callback for acceleration threshold reached
    void cb_reached(int16_t x, int16_t y, int16_t z, void *user_data) {
        (void)user_data; // avoid unused parameter warning

        printf("Acceleration(X): %fG\n", x/1000.0);
        printf("Acceleration(Y): %fG\n", y/1000.0);
        printf("Acceleration(Z): %fG\n", z/1000.0);
        printf("\n");
    }

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

        // Create device object
        Accelerometer acc;
        accelerometer_create(&acc, 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

        // Get threshold callbacks with a debounce time of 10 seconds (10000ms)
        accelerometer_set_debounce_period(&acc, 10000);

        // Register threshold reached callback to function cb_reached
        accelerometer_register_callback(&acc,
                                        ACCELEROMETER_CALLBACK_ACCELERATION_REACHED,
                                        (void *)cb_reached,
                                        NULL);

        // Configure threshold for acceleration values X, Y or Z greater than 2G
        accelerometer_set_acceleration_callback_threshold(&acc, '>', 2000, 0, 2000, 0, 2000, 0);

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

## 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

as defined in `ip_connection.h`.

All functions listed below are thread-safe.

### Basic Functions

void `accelerometer_create`(Accelerometer *accelerometer, const char *uid, IPConnection *ipcon)

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

      Accelerometer accelerometer;
      accelerometer_create(&accelerometer, "YOUR_DEVICE_UID", &ipcon);

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

void `accelerometer_destroy`(Accelerometer *accelerometer)

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

int `accelerometer_get_acceleration`(Accelerometer *accelerometer, int16_t *ret_x, int16_t *ret_y, int16_t *ret_z)

  Returns the acceleration in x, y and z direction. The values are given in mG (1/1000 G).

  If you want to get the acceleration periodically, it is recommended to use the callback `ACCELEROMETER_CALLBACK_ACCELERATION` and set the period with `accelerometer_set_acceleration_callback_period()`.

int `accelerometer_get_temperature`(Accelerometer *accelerometer, int16_t *ret_temperature)

  Returns the temperature of the accelerometer in °C.

int `accelerometer_led_on`(Accelerometer *accelerometer)

  Enables the LED on the Bricklet.

int `accelerometer_led_off`(Accelerometer *accelerometer)

  Disables the LED on the Bricklet.

int `accelerometer_is_led_on`(Accelerometer *accelerometer, uint8_t *ret_value)

  Returns true if the LED is enabled, false otherwise.

### Advanced Functions

int `accelerometer_set_configuration`(Accelerometer *accelerometer, uint8_t data_rate, uint8_t full_scale, uint8_t filter_bandwidth)

  Configures the data rate, full scale range and filter bandwidth. Possible values are:

  - Data rate of 0Hz to 1600Hz.
  - Full scale range of -2G to +2G up to -16G to +16G.
  - Filter bandwidth between 50Hz and 800Hz.

  Decreasing data rate or full scale range will also decrease the noise on the data.

  The default values are 100Hz data rate, -4G to +4G range and 200Hz filter bandwidth.

  The following defines are available for this function:

  - ACCELEROMETER_DATA_RATE_OFF = 0
  - ACCELEROMETER_DATA_RATE_3HZ = 1
  - ACCELEROMETER_DATA_RATE_6HZ = 2
  - ACCELEROMETER_DATA_RATE_12HZ = 3
  - ACCELEROMETER_DATA_RATE_25HZ = 4
  - ACCELEROMETER_DATA_RATE_50HZ = 5
  - ACCELEROMETER_DATA_RATE_100HZ = 6
  - ACCELEROMETER_DATA_RATE_400HZ = 7
  - ACCELEROMETER_DATA_RATE_800HZ = 8
  - ACCELEROMETER_DATA_RATE_1600HZ = 9
  - ACCELEROMETER_FULL_SCALE_2G = 0
  - ACCELEROMETER_FULL_SCALE_4G = 1
  - ACCELEROMETER_FULL_SCALE_6G = 2
  - ACCELEROMETER_FULL_SCALE_8G = 3
  - ACCELEROMETER_FULL_SCALE_16G = 4
  - ACCELEROMETER_FILTER_BANDWIDTH_800HZ = 0
  - ACCELEROMETER_FILTER_BANDWIDTH_400HZ = 1
  - ACCELEROMETER_FILTER_BANDWIDTH_200HZ = 2
  - ACCELEROMETER_FILTER_BANDWIDTH_50HZ = 3

int `accelerometer_get_configuration`(Accelerometer *accelerometer, uint8_t *ret_data_rate, uint8_t *ret_full_scale, uint8_t *ret_filter_bandwidth)

  Returns the configuration as set by `accelerometer_set_configuration()`.

  The following defines are available for this function:

  - ACCELEROMETER_DATA_RATE_OFF = 0
  - ACCELEROMETER_DATA_RATE_3HZ = 1
  - ACCELEROMETER_DATA_RATE_6HZ = 2
  - ACCELEROMETER_DATA_RATE_12HZ = 3
  - ACCELEROMETER_DATA_RATE_25HZ = 4
  - ACCELEROMETER_DATA_RATE_50HZ = 5
  - ACCELEROMETER_DATA_RATE_100HZ = 6
  - ACCELEROMETER_DATA_RATE_400HZ = 7
  - ACCELEROMETER_DATA_RATE_800HZ = 8
  - ACCELEROMETER_DATA_RATE_1600HZ = 9
  - ACCELEROMETER_FULL_SCALE_2G = 0
  - ACCELEROMETER_FULL_SCALE_4G = 1
  - ACCELEROMETER_FULL_SCALE_6G = 2
  - ACCELEROMETER_FULL_SCALE_8G = 3
  - ACCELEROMETER_FULL_SCALE_16G = 4
  - ACCELEROMETER_FILTER_BANDWIDTH_800HZ = 0
  - ACCELEROMETER_FILTER_BANDWIDTH_400HZ = 1
  - ACCELEROMETER_FILTER_BANDWIDTH_200HZ = 2
  - ACCELEROMETER_FILTER_BANDWIDTH_50HZ = 3

int `accelerometer_get_api_version`(Accelerometer *accelerometer, 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 `accelerometer_get_response_expected`(Accelerometer *accelerometer, 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 `accelerometer_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 `accelerometer_set_response_expected()` for the list of function ID defines available for this function.

int `accelerometer_set_response_expected`(Accelerometer *accelerometer, 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 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:

  - ACCELEROMETER_FUNCTION_SET_ACCELERATION_CALLBACK_PERIOD = 2
  - ACCELEROMETER_FUNCTION_SET_ACCELERATION_CALLBACK_THRESHOLD = 4
  - ACCELEROMETER_FUNCTION_SET_DEBOUNCE_PERIOD = 6
  - ACCELEROMETER_FUNCTION_SET_CONFIGURATION = 9
  - ACCELEROMETER_FUNCTION_LED_ON = 11
  - ACCELEROMETER_FUNCTION_LED_OFF = 12

int `accelerometer_set_response_expected_all`(Accelerometer *accelerometer, bool response_expected)

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

int `accelerometer_get_identity`(Accelerometer *accelerometer, 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 `accelerometer_register_callback`(Accelerometer *accelerometer, uint8_t id, void *callback, void *user_data)

  Registers a callback with ID `id` to the function `callback`. The `user_data` will be given as a parameter of the callback.

  The available IDs with corresponding function signatures are listed below.

int `accelerometer_set_acceleration_callback_period`(Accelerometer *accelerometer, uint32_t period)

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

  `ACCELEROMETER_CALLBACK_ACCELERATION` is only triggered if the acceleration has changed since the last triggering.

  The default value is 0.

int `accelerometer_get_acceleration_callback_period`(Accelerometer *accelerometer, uint32_t *ret_period)

  Returns the period as set by `accelerometer_set_acceleration_callback_period()`.

int `accelerometer_set_acceleration_callback_threshold`(Accelerometer *accelerometer, char option, int16_t min_x, int16_t max_x, int16_t min_y, int16_t max_y, int16_t min_z, int16_t max_z)

  Sets the thresholds for the `ACCELEROMETER_CALLBACK_ACCELERATION_REACHED` callback.

  The following options are possible:

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

  The default value is ('x', 0, 0, 0, 0, 0, 0).

  The following defines are available for this function:

  - ACCELEROMETER_THRESHOLD_OPTION_OFF = 'x'
  - ACCELEROMETER_THRESHOLD_OPTION_OUTSIDE = 'o'
  - ACCELEROMETER_THRESHOLD_OPTION_INSIDE = 'i'
  - ACCELEROMETER_THRESHOLD_OPTION_SMALLER = '<'
  - ACCELEROMETER_THRESHOLD_OPTION_GREATER = '>'

int `accelerometer_get_acceleration_callback_threshold`(Accelerometer *accelerometer, char *ret_option, int16_t *ret_min_x, int16_t *ret_max_x, int16_t *ret_min_y, int16_t *ret_max_y, int16_t *ret_min_z, int16_t *ret_max_z)

  Returns the threshold as set by `accelerometer_set_acceleration_callback_threshold()`.

  The following defines are available for this function:

  - ACCELEROMETER_THRESHOLD_OPTION_OFF = 'x'
  - ACCELEROMETER_THRESHOLD_OPTION_OUTSIDE = 'o'
  - ACCELEROMETER_THRESHOLD_OPTION_INSIDE = 'i'
  - ACCELEROMETER_THRESHOLD_OPTION_SMALLER = '<'
  - ACCELEROMETER_THRESHOLD_OPTION_GREATER = '>'

int `accelerometer_set_debounce_period`(Accelerometer *accelerometer, uint32_t debounce)

  Sets the period in ms with which the threshold callback

  - `ACCELEROMETER_CALLBACK_ACCELERATION_REACHED`

  is triggered, if the threshold

  - `accelerometer_set_acceleration_callback_threshold()`

  keeps being reached.

  The default value is 100.

int `accelerometer_get_debounce_period`(Accelerometer *accelerometer, uint32_t *ret_debounce)

  Returns the debounce period as set by `accelerometer_set_debounce_period()`.

### Callbacks

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

>     accelerometer_register_callback(&accelerometer, ACCELEROMETER_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.

`ACCELEROMETER_CALLBACK_ACCELERATION`

      void callback(int16_t x, int16_t y, int16_t z, void *user_data)

  This callback is triggered periodically with the period that is set by `accelerometer_set_acceleration_callback_period()`. The parameters are the X, Y and Z acceleration.

  `ACCELEROMETER_CALLBACK_ACCELERATION` is only triggered if the acceleration has changed since the last triggering.

`ACCELEROMETER_CALLBACK_ACCELERATION_REACHED`

      void callback(int16_t x, int16_t y, int16_t z, void *user_data)

  This callback is triggered when the threshold as set by `accelerometer_set_acceleration_callback_threshold()` is reached. The parameters are the X, Y and Z acceleration.

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

### Constants

`ACCELEROMETER_DEVICE_IDENTIFIER`

  This constant is used to identify a Accelerometer Bricklet.

  The `accelerometer_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.

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