C/C++ - Load Cell Bricklet 2.0

This is the description of the C/C++ API bindings for the Load Cell Bricklet 2.0. General information and technical specifications for the Load Cell Bricklet 2.0 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_load_cell_v2.h"

#define HOST "localhost"
#define PORT 4223
#define UID "XYZ" // Change XYZ to the UID of your Load Cell Bricklet 2.0

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

    // Create device object
    LoadCellV2 lc;
    load_cell_v2_create(&lc, 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 weight
    int32_t weight;
    if(load_cell_v2_get_weight(&lc, &weight) < 0) {
        fprintf(stderr, "Could not get weight, probably timeout\n");
        return 1;
    }

    printf("Weight: %d g\n", weight);

    printf("Press key to exit\n");
    getchar();
    load_cell_v2_destroy(&lc);
    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_load_cell_v2.h"

#define HOST "localhost"
#define PORT 4223
#define UID "XYZ" // Change XYZ to the UID of your Load Cell Bricklet 2.0

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

    printf("Weight: %d g\n", weight);
}

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

    // Create device object
    LoadCellV2 lc;
    load_cell_v2_create(&lc, 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 weight callback to function cb_weight
    load_cell_v2_register_callback(&lc,
                                   LOAD_CELL_V2_CALLBACK_WEIGHT,
                                   (void *)cb_weight,
                                   NULL);

    // Set period for weight callback to 1s (1000ms) without a threshold
    load_cell_v2_set_weight_callback_configuration(&lc, 1000, false, 'x', 0, 0);

    printf("Press key to exit\n");
    getchar();
    load_cell_v2_destroy(&lc);
    ipcon_destroy(&ipcon); // Calls ipcon_disconnect internally
    return 0;
}

Threshold

Download (example_threshold.c)

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#include <stdio.h>

#include "ip_connection.h"
#include "bricklet_load_cell_v2.h"

#define HOST "localhost"
#define PORT 4223
#define UID "XYZ" // Change XYZ to the UID of your Load Cell Bricklet 2.0

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

    printf("Weight: %d g\n", weight);
}

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

    // Create device object
    LoadCellV2 lc;
    load_cell_v2_create(&lc, 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 weight callback to function cb_weight
    load_cell_v2_register_callback(&lc,
                                   LOAD_CELL_V2_CALLBACK_WEIGHT,
                                   (void *)cb_weight,
                                   NULL);

    // Configure threshold for weight "greater than 200 g"
    // with a debounce period of 1s (1000ms)
    load_cell_v2_set_weight_callback_configuration(&lc, 1000, false, '>', 200, 0);

    printf("Press key to exit\n");
    getchar();
    load_cell_v2_destroy(&lc);
    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 load_cell_v2_create(LoadCellV2 *load_cell_v2, const char *uid, IPConnection *ipcon)

Creates the device object load_cell_v2 with the unique device ID uid and adds it to the IPConnection ipcon:

LoadCellV2 load_cell_v2;
load_cell_v2_create(&load_cell_v2, "YOUR_DEVICE_UID", &ipcon);

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

void load_cell_v2_destroy(LoadCellV2 *load_cell_v2)

Removes the device object load_cell_v2 from its IPConnection and destroys it. The device object cannot be used anymore afterwards.

int load_cell_v2_get_weight(LoadCellV2 *load_cell_v2, int32_t *ret_weight)

Returns the currently measured weight in grams.

If you want to get the value periodically, it is recommended to use the LOAD_CELL_V2_CALLBACK_WEIGHT callback. You can set the callback configuration with load_cell_v2_set_weight_callback_configuration().

int load_cell_v2_set_info_led_config(LoadCellV2 *load_cell_v2, uint8_t config)

Configures the info LED to be either turned off, turned on, or blink in heartbeat mode.

The following defines are available for this function:

  • LOAD_CELL_V2_INFO_LED_CONFIG_OFF = 0
  • LOAD_CELL_V2_INFO_LED_CONFIG_ON = 1
  • LOAD_CELL_V2_INFO_LED_CONFIG_SHOW_HEARTBEAT = 2
int load_cell_v2_get_info_led_config(LoadCellV2 *load_cell_v2, uint8_t *ret_config)

Returns the LED configuration as set by load_cell_v2_set_info_led_config()

The following defines are available for this function:

  • LOAD_CELL_V2_INFO_LED_CONFIG_OFF = 0
  • LOAD_CELL_V2_INFO_LED_CONFIG_ON = 1
  • LOAD_CELL_V2_INFO_LED_CONFIG_SHOW_HEARTBEAT = 2
int load_cell_v2_tare(LoadCellV2 *load_cell_v2)

Sets the currently measured weight as tare weight.

Advanced Functions

int load_cell_v2_set_moving_average(LoadCellV2 *load_cell_v2, uint16_t average)

Sets the length of a moving averaging for the weight value.

Setting the length to 1 will turn the averaging off. With less averaging, there is more noise on the data.

The range for the averaging is 1-100.

The default value is 4.

int load_cell_v2_get_moving_average(LoadCellV2 *load_cell_v2, uint16_t *ret_average)

Returns the length moving average as set by load_cell_v2_set_moving_average().

int load_cell_v2_calibrate(LoadCellV2 *load_cell_v2, uint32_t weight)

To calibrate your Load Cell Bricklet 2.0 you have to

  • empty the scale and call this function with 0 and
  • add a known weight to the scale and call this function with the weight in grams.

The calibration is saved in the flash of the Bricklet and only needs to be done once.

We recommend to use the Brick Viewer for calibration, you don't need to call this function in your source code.

int load_cell_v2_set_configuration(LoadCellV2 *load_cell_v2, uint8_t rate, uint8_t gain)

The measurement rate and gain are configurable.

The rate can be either 10Hz or 80Hz. A faster rate will produce more noise. It is additionally possible to add a moving average (see load_cell_v2_set_moving_average()) to the measurements.

The gain can be 128x, 64x or 32x. It represents a measurement range of ±20mV, ±40mV and ±80mV respectively. The Load Cell Bricklet uses an excitation voltage of 5V and most load cells use an output of 2mV/V. That means the voltage range is ±15mV for most load cells (i.e. gain of 128x is best). If you don't know what all of this means you should keep it at 128x, it will most likely be correct.

The default rate is 10Hz and the default gain is 128x.

The following defines are available for this function:

  • LOAD_CELL_V2_RATE_10HZ = 0
  • LOAD_CELL_V2_RATE_80HZ = 1
  • LOAD_CELL_V2_GAIN_128X = 0
  • LOAD_CELL_V2_GAIN_64X = 1
  • LOAD_CELL_V2_GAIN_32X = 2
int load_cell_v2_get_configuration(LoadCellV2 *load_cell_v2, uint8_t *ret_rate, uint8_t *ret_gain)

Returns the configuration as set by load_cell_v2_set_configuration().

The following defines are available for this function:

  • LOAD_CELL_V2_RATE_10HZ = 0
  • LOAD_CELL_V2_RATE_80HZ = 1
  • LOAD_CELL_V2_GAIN_128X = 0
  • LOAD_CELL_V2_GAIN_64X = 1
  • LOAD_CELL_V2_GAIN_32X = 2
int load_cell_v2_get_api_version(LoadCellV2 *load_cell_v2, 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 load_cell_v2_get_response_expected(LoadCellV2 *load_cell_v2, 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 load_cell_v2_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 load_cell_v2_set_response_expected() for the list of function ID defines available for this function.

int load_cell_v2_set_response_expected(LoadCellV2 *load_cell_v2, 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:

  • LOAD_CELL_V2_FUNCTION_SET_WEIGHT_CALLBACK_CONFIGURATION = 2
  • LOAD_CELL_V2_FUNCTION_SET_MOVING_AVERAGE = 5
  • LOAD_CELL_V2_FUNCTION_SET_INFO_LED_CONFIG = 7
  • LOAD_CELL_V2_FUNCTION_CALIBRATE = 9
  • LOAD_CELL_V2_FUNCTION_TARE = 10
  • LOAD_CELL_V2_FUNCTION_SET_CONFIGURATION = 11
  • LOAD_CELL_V2_FUNCTION_SET_WRITE_FIRMWARE_POINTER = 237
  • LOAD_CELL_V2_FUNCTION_SET_STATUS_LED_CONFIG = 239
  • LOAD_CELL_V2_FUNCTION_RESET = 243
  • LOAD_CELL_V2_FUNCTION_WRITE_UID = 248
int load_cell_v2_set_response_expected_all(LoadCellV2 *load_cell_v2, bool response_expected)

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

int load_cell_v2_get_spitfp_error_count(LoadCellV2 *load_cell_v2, 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 load_cell_v2_set_bootloader_mode(LoadCellV2 *load_cell_v2, 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:

  • LOAD_CELL_V2_BOOTLOADER_MODE_BOOTLOADER = 0
  • LOAD_CELL_V2_BOOTLOADER_MODE_FIRMWARE = 1
  • LOAD_CELL_V2_BOOTLOADER_MODE_BOOTLOADER_WAIT_FOR_REBOOT = 2
  • LOAD_CELL_V2_BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_REBOOT = 3
  • LOAD_CELL_V2_BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_ERASE_AND_REBOOT = 4
  • LOAD_CELL_V2_BOOTLOADER_STATUS_OK = 0
  • LOAD_CELL_V2_BOOTLOADER_STATUS_INVALID_MODE = 1
  • LOAD_CELL_V2_BOOTLOADER_STATUS_NO_CHANGE = 2
  • LOAD_CELL_V2_BOOTLOADER_STATUS_ENTRY_FUNCTION_NOT_PRESENT = 3
  • LOAD_CELL_V2_BOOTLOADER_STATUS_DEVICE_IDENTIFIER_INCORRECT = 4
  • LOAD_CELL_V2_BOOTLOADER_STATUS_CRC_MISMATCH = 5
int load_cell_v2_get_bootloader_mode(LoadCellV2 *load_cell_v2, uint8_t *ret_mode)

Returns the current bootloader mode, see load_cell_v2_set_bootloader_mode().

The following defines are available for this function:

  • LOAD_CELL_V2_BOOTLOADER_MODE_BOOTLOADER = 0
  • LOAD_CELL_V2_BOOTLOADER_MODE_FIRMWARE = 1
  • LOAD_CELL_V2_BOOTLOADER_MODE_BOOTLOADER_WAIT_FOR_REBOOT = 2
  • LOAD_CELL_V2_BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_REBOOT = 3
  • LOAD_CELL_V2_BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_ERASE_AND_REBOOT = 4
int load_cell_v2_set_write_firmware_pointer(LoadCellV2 *load_cell_v2, uint32_t pointer)

Sets the firmware pointer for load_cell_v2_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 load_cell_v2_write_firmware(LoadCellV2 *load_cell_v2, uint8_t data[64], uint8_t *ret_status)

Writes 64 Bytes of firmware at the position as written by load_cell_v2_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 load_cell_v2_set_status_led_config(LoadCellV2 *load_cell_v2, 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:

  • LOAD_CELL_V2_STATUS_LED_CONFIG_OFF = 0
  • LOAD_CELL_V2_STATUS_LED_CONFIG_ON = 1
  • LOAD_CELL_V2_STATUS_LED_CONFIG_SHOW_HEARTBEAT = 2
  • LOAD_CELL_V2_STATUS_LED_CONFIG_SHOW_STATUS = 3
int load_cell_v2_get_status_led_config(LoadCellV2 *load_cell_v2, uint8_t *ret_config)

Returns the configuration as set by load_cell_v2_set_status_led_config()

The following defines are available for this function:

  • LOAD_CELL_V2_STATUS_LED_CONFIG_OFF = 0
  • LOAD_CELL_V2_STATUS_LED_CONFIG_ON = 1
  • LOAD_CELL_V2_STATUS_LED_CONFIG_SHOW_HEARTBEAT = 2
  • LOAD_CELL_V2_STATUS_LED_CONFIG_SHOW_STATUS = 3
int load_cell_v2_get_chip_temperature(LoadCellV2 *load_cell_v2, 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 load_cell_v2_reset(LoadCellV2 *load_cell_v2)

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 load_cell_v2_write_uid(LoadCellV2 *load_cell_v2, 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 load_cell_v2_read_uid(LoadCellV2 *load_cell_v2, uint32_t *ret_uid)

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

int load_cell_v2_get_identity(LoadCellV2 *load_cell_v2, 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 load_cell_v2_register_callback(LoadCellV2 *load_cell_v2, 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 load_cell_v2_set_weight_callback_configuration(LoadCellV2 *load_cell_v2, uint32_t period, bool value_has_to_change, char option, int32_t min, int32_t max)

The period in ms is the period with which the LOAD_CELL_V2_CALLBACK_WEIGHT callback is triggered periodically. A value of 0 turns the callback off.

If the value has to change-parameter is set to true, the callback is only triggered after the value has changed. If the value didn't change within the period, the callback is triggered immediately on change.

If it is set to false, the callback is continuously triggered with the period, independent of the value.

It is furthermore possible to constrain the callback with thresholds.

The option-parameter together with min/max sets a threshold for the LOAD_CELL_V2_CALLBACK_WEIGHT callback.

The following options are possible:

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

If the option is set to 'x' (threshold turned off) the callback is triggered with the fixed period.

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

The following defines are available for this function:

  • LOAD_CELL_V2_THRESHOLD_OPTION_OFF = 'x'
  • LOAD_CELL_V2_THRESHOLD_OPTION_OUTSIDE = 'o'
  • LOAD_CELL_V2_THRESHOLD_OPTION_INSIDE = 'i'
  • LOAD_CELL_V2_THRESHOLD_OPTION_SMALLER = '<'
  • LOAD_CELL_V2_THRESHOLD_OPTION_GREATER = '>'
int load_cell_v2_get_weight_callback_configuration(LoadCellV2 *load_cell_v2, uint32_t *ret_period, bool *ret_value_has_to_change, char *ret_option, int32_t *ret_min, int32_t *ret_max)

Returns the callback configuration as set by load_cell_v2_set_weight_callback_configuration().

The following defines are available for this function:

  • LOAD_CELL_V2_THRESHOLD_OPTION_OFF = 'x'
  • LOAD_CELL_V2_THRESHOLD_OPTION_OUTSIDE = 'o'
  • LOAD_CELL_V2_THRESHOLD_OPTION_INSIDE = 'i'
  • LOAD_CELL_V2_THRESHOLD_OPTION_SMALLER = '<'
  • LOAD_CELL_V2_THRESHOLD_OPTION_GREATER = '>'

Callbacks

Callbacks can be registered to receive time critical or recurring data from the device. The registration is done with the load_cell_v2_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);
}

load_cell_v2_register_callback(&load_cell_v2, LOAD_CELL_V2_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.

LOAD_CELL_V2_CALLBACK_WEIGHT
void callback(int32_t weight, void *user_data)

This callback is triggered periodically according to the configuration set by load_cell_v2_set_weight_callback_configuration().

The parameter is the same as load_cell_v2_get_weight().

Constants

LOAD_CELL_V2_DEVICE_IDENTIFIER

This constant is used to identify a Load Cell Bricklet 2.0.

The load_cell_v2_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.

LOAD_CELL_V2_DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Load Cell Bricklet 2.0.