C/C++ - Stepper Brick

This is the description of the C/C++ API bindings for the Stepper Brick. General information and technical specifications for the Stepper Brick 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).

Configuration

Download (example_configuration.c)

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#include <stdio.h>

#include "ip_connection.h"
#include "brick_stepper.h"

#define HOST "localhost"
#define PORT 4223
#define UID "XXYYZZ" // Change XXYYZZ to the UID of your Stepper Brick

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

    // Create device object
    Stepper stepper;
    stepper_create(&stepper, 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

    stepper_set_motor_current(&stepper, 800); // 800mA
    stepper_set_step_mode(&stepper, 8); // 1/8 step mode
    stepper_set_max_velocity(&stepper, 2000); // Velocity 2000 steps/s

    // Slow acceleration (500 steps/s^2),
    // Fast deacceleration (5000 steps/s^2)
    stepper_set_speed_ramping(&stepper, 500, 5000);

    stepper_enable(&stepper); // Enable motor power
    stepper_set_steps(&stepper, 60000); // Drive 60000 steps forward

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

Callback

Download (example_callback.c)

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#include <stdio.h>
#include <stdlib.h>

#include "ip_connection.h"
#include "brick_stepper.h"

#define HOST "localhost"
#define PORT 4223
#define UID "XXYYZZ" // Change XXYYZZ to the UID of your Stepper Brick

// Use position reached callback to program random movement
void cb_position_reached(int32_t position, void *user_data) {
    (void)position; // avoid unused parameter warning

    Stepper *stepper = (Stepper *)user_data;
    int32_t steps;

    if(rand() % 2) {
        steps = (rand() % 4000) + 1000; // steps (forward)
        printf("Driving forward: %d steps\n", steps);
    } else {
        steps = -((rand() % 4000) + 1000); // steps (backward)
        printf("Driving backward: %d steps\n", steps);
    }

    int16_t vel = (rand() % 1800) + 200; // steps/s
    uint16_t acc = (rand() % 900) + 100; // steps/s^2
    uint16_t dec = (rand() % 900) + 100; // steps/s^2

    printf("Configuration (vel, acc, dec): %d, %d %d\n", vel, acc, dec);

    stepper_set_speed_ramping(stepper, acc, dec);
    stepper_set_max_velocity(stepper, vel);
    stepper_set_steps(stepper, steps);
}

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

    // Create device object
    Stepper stepper;
    stepper_create(&stepper, 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 position reached callback to function cb_position_reached
    stepper_register_callback(&stepper,
                              STEPPER_CALLBACK_POSITION_REACHED,
                              (void *)cb_position_reached,
                              &stepper);

    stepper_enable(&stepper); // Enable motor power
    stepper_set_steps(&stepper, 1); // Drive one step forward to get things going

    printf("Press key to exit\n");
    getchar();
    stepper_disable(&stepper);
    stepper_destroy(&stepper);
    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 stepper_create(Stepper *stepper, const char *uid, IPConnection *ipcon)

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

Stepper stepper;
stepper_create(&stepper, "YOUR_DEVICE_UID", &ipcon);

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

void stepper_destroy(Stepper *stepper)

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

int stepper_set_max_velocity(Stepper *stepper, uint16_t velocity)

Sets the maximum velocity of the stepper motor in steps per second. This function does not start the motor, it merely sets the maximum velocity the stepper motor is accelerated to. To get the motor running use either stepper_set_target_position(), stepper_set_steps(), stepper_drive_forward() or stepper_drive_backward().

int stepper_get_max_velocity(Stepper *stepper, uint16_t *ret_velocity)

Returns the velocity as set by stepper_set_max_velocity().

int stepper_get_current_velocity(Stepper *stepper, uint16_t *ret_velocity)

Returns the current velocity of the stepper motor in steps per second.

int stepper_set_speed_ramping(Stepper *stepper, uint16_t acceleration, uint16_t deacceleration)

Sets the acceleration and deacceleration of the stepper motor. The values are given in steps/s². An acceleration of 1000 means, that every second the velocity is increased by 1000 steps/s.

For example: If the current velocity is 0 and you want to accelerate to a velocity of 8000 steps/s in 10 seconds, you should set an acceleration of 800 steps/s².

An acceleration/deacceleration of 0 means instantaneous acceleration/deacceleration (not recommended)

The default value is 1000 for both

int stepper_get_speed_ramping(Stepper *stepper, uint16_t *ret_acceleration, uint16_t *ret_deacceleration)

Returns the acceleration and deacceleration as set by stepper_set_speed_ramping().

int stepper_full_brake(Stepper *stepper)

Executes an active full brake.

Warning

This function is for emergency purposes, where an immediate brake is necessary. Depending on the current velocity and the strength of the motor, a full brake can be quite violent.

Call stepper_stop() if you just want to stop the motor.

int stepper_set_steps(Stepper *stepper, int32_t steps)

Sets the number of steps the stepper motor should run. Positive values will drive the motor forward and negative values backward. The velocity, acceleration and deacceleration as set by stepper_set_max_velocity() and stepper_set_speed_ramping() will be used.

int stepper_get_steps(Stepper *stepper, int32_t *ret_steps)

Returns the last steps as set by stepper_set_steps().

int stepper_get_remaining_steps(Stepper *stepper, int32_t *ret_steps)

Returns the remaining steps of the last call of stepper_set_steps(). For example, if stepper_set_steps() is called with 2000 and stepper_get_remaining_steps() is called after the motor has run for 500 steps, it will return 1500.

int stepper_drive_forward(Stepper *stepper)

Drives the stepper motor forward until stepper_drive_backward() or stepper_stop() is called. The velocity, acceleration and deacceleration as set by stepper_set_max_velocity() and stepper_set_speed_ramping() will be used.

int stepper_drive_backward(Stepper *stepper)

Drives the stepper motor backward until stepper_drive_forward() or stepper_stop() is triggered. The velocity, acceleration and deacceleration as set by stepper_set_max_velocity() and stepper_set_speed_ramping() will be used.

int stepper_stop(Stepper *stepper)

Stops the stepper motor with the deacceleration as set by stepper_set_speed_ramping().

int stepper_set_motor_current(Stepper *stepper, uint16_t current)

Sets the current in mA with which the motor will be driven. The minimum value is 100mA, the maximum value 2291mA and the default value is 800mA.

Warning

Do not set this value above the specifications of your stepper motor. Otherwise it may damage your motor.

int stepper_get_motor_current(Stepper *stepper, uint16_t *ret_current)

Returns the current as set by stepper_set_motor_current().

int stepper_enable(Stepper *stepper)

Enables the driver chip. The driver parameters can be configured (maximum velocity, acceleration, etc) before it is enabled.

int stepper_disable(Stepper *stepper)

Disables the driver chip. The configurations are kept (maximum velocity, acceleration, etc) but the motor is not driven until it is enabled again.

int stepper_is_enabled(Stepper *stepper, bool *ret_enabled)

Returns true if the driver chip is enabled, false otherwise.

Advanced Functions

int stepper_set_current_position(Stepper *stepper, int32_t position)

Sets the current steps of the internal step counter. This can be used to set the current position to 0 when some kind of starting position is reached (e.g. when a CNC machine reaches a corner).

int stepper_get_current_position(Stepper *stepper, int32_t *ret_position)

Returns the current position of the stepper motor in steps. On startup the position is 0. The steps are counted with all possible driving functions (stepper_set_target_position(), stepper_set_steps(), stepper_drive_forward() or stepper_drive_backward()). It also is possible to reset the steps to 0 or set them to any other desired value with stepper_set_current_position().

int stepper_set_target_position(Stepper *stepper, int32_t position)

Sets the target position of the stepper motor in steps. For example, if the current position of the motor is 500 and stepper_set_target_position() is called with 1000, the stepper motor will drive 500 steps forward. It will use the velocity, acceleration and deacceleration as set by stepper_set_max_velocity() and stepper_set_speed_ramping().

A call of stepper_set_target_position() with the parameter x is equivalent to a call of stepper_set_steps() with the parameter (x - stepper_get_current_position()).

int stepper_get_target_position(Stepper *stepper, int32_t *ret_position)

Returns the last target position as set by stepper_set_target_position().

int stepper_set_step_mode(Stepper *stepper, uint8_t mode)

Sets the step mode of the stepper motor. Possible values are:

  • Full Step = 1
  • Half Step = 2
  • Quarter Step = 4
  • Eighth Step = 8

A higher value will increase the resolution and decrease the torque of the stepper motor.

The default value is 8 (Eighth Step).

The following defines are available for this function:

  • STEPPER_STEP_MODE_FULL_STEP = 1
  • STEPPER_STEP_MODE_HALF_STEP = 2
  • STEPPER_STEP_MODE_QUARTER_STEP = 4
  • STEPPER_STEP_MODE_EIGHTH_STEP = 8
int stepper_get_step_mode(Stepper *stepper, uint8_t *ret_mode)

Returns the step mode as set by stepper_set_step_mode().

The following defines are available for this function:

  • STEPPER_STEP_MODE_FULL_STEP = 1
  • STEPPER_STEP_MODE_HALF_STEP = 2
  • STEPPER_STEP_MODE_QUARTER_STEP = 4
  • STEPPER_STEP_MODE_EIGHTH_STEP = 8
int stepper_get_stack_input_voltage(Stepper *stepper, uint16_t *ret_voltage)

Returns the stack input voltage in mV. The stack input voltage is the voltage that is supplied via the stack, i.e. it is given by a Step-Down or Step-Up Power Supply.

int stepper_get_external_input_voltage(Stepper *stepper, uint16_t *ret_voltage)

Returns the external input voltage in mV. The external input voltage is given via the black power input connector on the Stepper Brick.

If there is an external input voltage and a stack input voltage, the motor will be driven by the external input voltage. If there is only a stack voltage present, the motor will be driven by this voltage.

Warning

This means, if you have a high stack voltage and a low external voltage, the motor will be driven with the low external voltage. If you then remove the external connection, it will immediately be driven by the high stack voltage

int stepper_get_current_consumption(Stepper *stepper, uint16_t *ret_current)

Returns the current consumption of the motor in mA.

int stepper_set_decay(Stepper *stepper, uint16_t decay)

Sets the decay mode of the stepper motor. The possible value range is between 0 and 65535. A value of 0 sets the fast decay mode, a value of 65535 sets the slow decay mode and a value in between sets the mixed decay mode.

Changing the decay mode is only possible if synchronous rectification is enabled (see stepper_set_sync_rect()).

For a good explanation of the different decay modes see this blog post by Avayan.

A good decay mode is unfortunately different for every motor. The best way to work out a good decay mode for your stepper motor, if you can't measure the current with an oscilloscope, is to listen to the sound of the motor. If the value is too low, you often hear a high pitched sound and if it is too high you can often hear a humming sound.

Generally, fast decay mode (small value) will be noisier but also allow higher motor speeds.

The default value is 10000.

Note

There is unfortunately no formula to calculate a perfect decay mode for a given stepper motor. If you have problems with loud noises or the maximum motor speed is too slow, you should try to tinker with the decay value

int stepper_get_decay(Stepper *stepper, uint16_t *ret_decay)

Returns the decay mode as set by stepper_set_decay().

int stepper_set_sync_rect(Stepper *stepper, bool sync_rect)

Turns synchronous rectification on or off (true or false).

With synchronous rectification on, the decay can be changed (see stepper_set_decay()). Without synchronous rectification fast decay is used.

For an explanation of synchronous rectification see here.

Warning

If you want to use high speeds (> 10000 steps/s) for a large stepper motor with a large inductivity we strongly suggest that you disable synchronous rectification. Otherwise the Brick may not be able to cope with the load and overheat.

The default value is false.

int stepper_is_sync_rect(Stepper *stepper, bool *ret_sync_rect)

Returns true if synchronous rectification is enabled, false otherwise.

int stepper_set_time_base(Stepper *stepper, uint32_t time_base)

Sets the time base of the velocity and the acceleration of the stepper brick (in seconds).

For example, if you want to make one step every 1.5 seconds, you can set the time base to 15 and the velocity to 10. Now the velocity is 10steps/15s = 1steps/1.5s.

The default value is 1.

int stepper_get_time_base(Stepper *stepper, uint32_t *ret_time_base)

Returns the time base as set by stepper_set_time_base().

int stepper_get_all_data(Stepper *stepper, uint16_t *ret_current_velocity, int32_t *ret_current_position, int32_t *ret_remaining_steps, uint16_t *ret_stack_voltage, uint16_t *ret_external_voltage, uint16_t *ret_current_consumption)

Returns the following parameters: The current velocity, the current position, the remaining steps, the stack voltage, the external voltage and the current consumption of the stepper motor.

There is also a callback for this function, see STEPPER_CALLBACK_ALL_DATA callback.

int stepper_get_api_version(Stepper *stepper, 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 stepper_get_response_expected(Stepper *stepper, 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 stepper_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 stepper_set_response_expected() for the list of function ID defines available for this function.

int stepper_set_response_expected(Stepper *stepper, 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:

  • STEPPER_FUNCTION_SET_MAX_VELOCITY = 1
  • STEPPER_FUNCTION_SET_SPEED_RAMPING = 4
  • STEPPER_FUNCTION_FULL_BRAKE = 6
  • STEPPER_FUNCTION_SET_CURRENT_POSITION = 7
  • STEPPER_FUNCTION_SET_TARGET_POSITION = 9
  • STEPPER_FUNCTION_SET_STEPS = 11
  • STEPPER_FUNCTION_SET_STEP_MODE = 14
  • STEPPER_FUNCTION_DRIVE_FORWARD = 16
  • STEPPER_FUNCTION_DRIVE_BACKWARD = 17
  • STEPPER_FUNCTION_STOP = 18
  • STEPPER_FUNCTION_SET_MOTOR_CURRENT = 22
  • STEPPER_FUNCTION_ENABLE = 24
  • STEPPER_FUNCTION_DISABLE = 25
  • STEPPER_FUNCTION_SET_DECAY = 27
  • STEPPER_FUNCTION_SET_MINIMUM_VOLTAGE = 29
  • STEPPER_FUNCTION_SET_SYNC_RECT = 33
  • STEPPER_FUNCTION_SET_TIME_BASE = 35
  • STEPPER_FUNCTION_SET_ALL_DATA_PERIOD = 38
  • STEPPER_FUNCTION_SET_SPITFP_BAUDRATE_CONFIG = 231
  • STEPPER_FUNCTION_SET_SPITFP_BAUDRATE = 234
  • STEPPER_FUNCTION_ENABLE_STATUS_LED = 238
  • STEPPER_FUNCTION_DISABLE_STATUS_LED = 239
  • STEPPER_FUNCTION_RESET = 243
int stepper_set_response_expected_all(Stepper *stepper, bool response_expected)

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

int stepper_set_spitfp_baudrate_config(Stepper *stepper, bool enable_dynamic_baudrate, uint32_t minimum_dynamic_baudrate)

The SPITF protocol can be used with a dynamic baudrate. If the dynamic baudrate is enabled, the Brick will try to adapt the baudrate for the communication between Bricks and Bricklets according to the amount of data that is transferred.

The baudrate will be increased exponentially if lots of data is send/received and decreased linearly if little data is send/received.

This lowers the baudrate in applications where little data is transferred (e.g. a weather station) and increases the robustness. If there is lots of data to transfer (e.g. Thermal Imaging Bricklet) it automatically increases the baudrate as needed.

In cases where some data has to transferred as fast as possible every few seconds (e.g. RS485 Bricklet with a high baudrate but small payload) you may want to turn the dynamic baudrate off to get the highest possible performance.

The maximum value of the baudrate can be set per port with the function stepper_set_spitfp_baudrate(). If the dynamic baudrate is disabled, the baudrate as set by stepper_set_spitfp_baudrate() will be used statically.

The minimum dynamic baudrate has a value range of 400000 to 2000000 baud.

By default dynamic baudrate is enabled and the minimum dynamic baudrate is 400000.

New in version 2.3.6 (Firmware).

int stepper_get_spitfp_baudrate_config(Stepper *stepper, bool *ret_enable_dynamic_baudrate, uint32_t *ret_minimum_dynamic_baudrate)

Returns the baudrate config, see stepper_set_spitfp_baudrate_config().

New in version 2.3.6 (Firmware).

int stepper_get_send_timeout_count(Stepper *stepper, uint8_t communication_method, uint32_t *ret_timeout_count)

Returns the timeout count for the different communication methods.

The methods 0-2 are available for all Bricks, 3-7 only for Master Bricks.

This function is mostly used for debugging during development, in normal operation the counters should nearly always stay at 0.

The following defines are available for this function:

  • STEPPER_COMMUNICATION_METHOD_NONE = 0
  • STEPPER_COMMUNICATION_METHOD_USB = 1
  • STEPPER_COMMUNICATION_METHOD_SPI_STACK = 2
  • STEPPER_COMMUNICATION_METHOD_CHIBI = 3
  • STEPPER_COMMUNICATION_METHOD_RS485 = 4
  • STEPPER_COMMUNICATION_METHOD_WIFI = 5
  • STEPPER_COMMUNICATION_METHOD_ETHERNET = 6
  • STEPPER_COMMUNICATION_METHOD_WIFI_V2 = 7

New in version 2.3.4 (Firmware).

int stepper_set_spitfp_baudrate(Stepper *stepper, char bricklet_port, uint32_t baudrate)

Sets the baudrate for a specific Bricklet port ('a' - 'd'). The baudrate can be in the range 400000 to 2000000.

If you want to increase the throughput of Bricklets you can increase the baudrate. If you get a high error count because of high interference (see stepper_get_spitfp_error_count()) you can decrease the baudrate.

If the dynamic baudrate feature is enabled, the baudrate set by this function corresponds to the maximum baudrate (see stepper_set_spitfp_baudrate_config()).

Regulatory testing is done with the default baudrate. If CE compatibility or similar is necessary in you applications we recommend to not change the baudrate.

The default baudrate for all ports is 1400000.

New in version 2.3.3 (Firmware).

int stepper_get_spitfp_baudrate(Stepper *stepper, char bricklet_port, uint32_t *ret_baudrate)

Returns the baudrate for a given Bricklet port, see stepper_set_spitfp_baudrate().

New in version 2.3.3 (Firmware).

int stepper_get_spitfp_error_count(Stepper *stepper, char bricklet_port, 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 Brick side. All Bricklets have a similar function that returns the errors on the Bricklet side.

New in version 2.3.3 (Firmware).

int stepper_enable_status_led(Stepper *stepper)

Enables the status LED.

The status LED is the blue LED next to the USB connector. If enabled is is on and it flickers if data is transfered. If disabled it is always off.

The default state is enabled.

New in version 2.3.1 (Firmware).

int stepper_disable_status_led(Stepper *stepper)

Disables the status LED.

The status LED is the blue LED next to the USB connector. If enabled is is on and it flickers if data is transfered. If disabled it is always off.

The default state is enabled.

New in version 2.3.1 (Firmware).

int stepper_is_status_led_enabled(Stepper *stepper, bool *ret_enabled)

Returns true if the status LED is enabled, false otherwise.

New in version 2.3.1 (Firmware).

int stepper_get_protocol1_bricklet_name(Stepper *stepper, char port, uint8_t *ret_protocol_version, uint8_t ret_firmware_version[3], char ret_name[40])

Returns the firmware and protocol version and the name of the Bricklet for a given port.

This functions sole purpose is to allow automatic flashing of v1.x.y Bricklet plugins.

int stepper_get_chip_temperature(Stepper *stepper, int16_t *ret_temperature)

Returns the temperature in °C/10 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 an accuracy of +-15%. Practically it is only useful as an indicator for temperature changes.

int stepper_reset(Stepper *stepper)

Calling this function will reset the Brick. Calling this function on a Brick inside of a stack will reset the whole stack.

After a reset you have to create new device objects, calling functions on the existing ones will result in undefined behavior!

int stepper_get_identity(Stepper *stepper, 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 Brick is connected to, the position, the hardware and firmware version as well as the device identifier.

The position can be '0'-'8' (stack position).

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

Callback Configuration Functions

void stepper_register_callback(Stepper *stepper, 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 stepper_set_minimum_voltage(Stepper *stepper, uint16_t voltage)

Sets the minimum voltage in mV, below which the STEPPER_CALLBACK_UNDER_VOLTAGE callback is triggered. The minimum possible value that works with the Stepper Brick is 8V. You can use this function to detect the discharge of a battery that is used to drive the stepper motor. If you have a fixed power supply, you likely do not need this functionality.

The default value is 8V.

int stepper_get_minimum_voltage(Stepper *stepper, uint16_t *ret_voltage)

Returns the minimum voltage as set by stepper_set_minimum_voltage().

int stepper_set_all_data_period(Stepper *stepper, uint32_t period)

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

int stepper_get_all_data_period(Stepper *stepper, uint32_t *ret_period)

Returns the period as set by stepper_set_all_data_period().

Callbacks

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

stepper_register_callback(&stepper, STEPPER_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.

STEPPER_CALLBACK_UNDER_VOLTAGE
void callback(uint16_t voltage, void *user_data)

This callback is triggered when the input voltage drops below the value set by stepper_set_minimum_voltage(). The parameter is the current voltage given in mV.

STEPPER_CALLBACK_POSITION_REACHED
void callback(int32_t position, void *user_data)

This callback is triggered when a position set by stepper_set_steps() or stepper_set_target_position() is reached.

Note

Since we can't get any feedback from the stepper motor, this only works if the acceleration (see stepper_set_speed_ramping()) is set smaller or equal to the maximum acceleration of the motor. Otherwise the motor will lag behind the control value and the callback will be triggered too early.

STEPPER_CALLBACK_ALL_DATA
void callback(uint16_t current_velocity, int32_t current_position, int32_t remaining_steps, uint16_t stack_voltage, uint16_t external_voltage, uint16_t current_consumption, void *user_data)

This callback is triggered periodically with the period that is set by stepper_set_all_data_period(). The parameters are: the current velocity, the current position, the remaining steps, the stack voltage, the external voltage and the current consumption of the stepper motor.

STEPPER_CALLBACK_NEW_STATE
void callback(uint8_t state_new, uint8_t state_previous, void *user_data)

This callback is triggered whenever the Stepper Brick enters a new state. It returns the new state as well as the previous state.

The following defines are available for this function:

  • STEPPER_STATE_STOP = 1
  • STEPPER_STATE_ACCELERATION = 2
  • STEPPER_STATE_RUN = 3
  • STEPPER_STATE_DEACCELERATION = 4
  • STEPPER_STATE_DIRECTION_CHANGE_TO_FORWARD = 5
  • STEPPER_STATE_DIRECTION_CHANGE_TO_BACKWARD = 6

Constants

STEPPER_DEVICE_IDENTIFIER

This constant is used to identify a Stepper Brick.

The stepper_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.

STEPPER_DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Stepper Brick.