C/C++ - DC Brick

This is the description of the C/C++ API bindings for the DC Brick. General information and technical specifications for the DC 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_dc.h"

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

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

    // Create device object
    DC dc;
    dc_create(&dc, 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

    dc_set_drive_mode(&dc, DC_DRIVE_MODE_DRIVE_COAST);
    dc_set_pwm_frequency(&dc, 10000); // Use PWM frequency of 10kHz
    dc_set_acceleration(&dc, 5000); // Slow acceleration
    dc_set_velocity(&dc, 32767); // Full speed forward
    dc_enable(&dc); // Enable motor power

    printf("Press key to exit\n");
    getchar();
    dc_disable(&dc); // Disable motor power
    dc_destroy(&dc);
    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 "brick_dc.h"

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

// Use velocity reached callback to swing back and forth
// between full speed forward and full speed backward
void cb_velocity_reached(int16_t velocity, void *user_data) {
    DC *dc = (DC *)user_data;

    if(velocity == 32767) {
        printf("Velocity: Full speed forward, now turning backward\n");
        dc_set_velocity(dc, -32767);
    } else if(velocity == -32767) {
        printf("Velocity: Full speed backward, now turning forward\n");
        dc_set_velocity(dc, 32767);
    } else {
        printf("Error\n"); // Can only happen if another program sets velocity
    }
}

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

    // Create device object
    DC dc;
    dc_create(&dc, 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

    // The acceleration has to be smaller or equal to the maximum
    // acceleration of the DC motor, otherwise the velocity reached
    // callback will be called too early
    dc_set_acceleration(&dc, 5000); // Slow acceleration
    dc_set_velocity(&dc, 32767); // Full speed forward

    // Register velocity reached callback to function cb_velocity_reached
    dc_register_callback(&dc,
                         DC_CALLBACK_VELOCITY_REACHED,
                         (void *)cb_velocity_reached,
                         &dc);

    // Enable motor power
    dc_enable(&dc);

    printf("Press key to exit\n");
    getchar();
    dc_disable(&dc); // Disable motor power
    dc_destroy(&dc);
    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 dc_create(DC *dc, const char *uid, IPConnection *ipcon)

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

DC dc;
dc_create(&dc, "YOUR_DEVICE_UID", &ipcon);

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

void dc_destroy(DC *dc)

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

int dc_set_velocity(DC *dc, int16_t velocity)

Sets the velocity of the motor. Whereas -32767 is full speed backward, 0 is stop and 32767 is full speed forward. Depending on the acceleration (see dc_set_acceleration()), the motor is not immediately brought to the velocity but smoothly accelerated.

The velocity describes the duty cycle of the PWM with which the motor is controlled, e.g. a velocity of 3277 sets a PWM with a 10% duty cycle. You can not only control the duty cycle of the PWM but also the frequency, see dc_set_pwm_frequency().

The default velocity is 0.

int dc_get_velocity(DC *dc, int16_t *ret_velocity)

Returns the velocity as set by dc_set_velocity().

int dc_get_current_velocity(DC *dc, int16_t *ret_velocity)

Returns the current velocity of the motor. This value is different from dc_get_velocity() whenever the motor is currently accelerating to a goal set by dc_set_velocity().

int dc_set_acceleration(DC *dc, uint16_t acceleration)

Sets the acceleration of the motor. It is given in velocity/s. An acceleration of 10000 means, that every second the velocity is increased by 10000 (or about 30% duty cycle).

For example: If the current velocity is 0 and you want to accelerate to a velocity of 16000 (about 50% duty cycle) in 10 seconds, you should set an acceleration of 1600.

If acceleration is set to 0, there is no speed ramping, i.e. a new velocity is immediately given to the motor.

The default acceleration is 10000.

int dc_get_acceleration(DC *dc, uint16_t *ret_acceleration)

Returns the acceleration as set by dc_set_acceleration().

int dc_full_brake(DC *dc)

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 dc_set_velocity() with 0 if you just want to stop the motor.

int dc_enable(DC *dc)

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

int dc_disable(DC *dc)

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

int dc_is_enabled(DC *dc, bool *ret_enabled)

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

Advanced Functions

int dc_set_pwm_frequency(DC *dc, uint16_t frequency)

Sets the frequency (in Hz) of the PWM with which the motor is driven. The possible range of the frequency is 1-20000Hz. Often a high frequency is less noisy and the motor runs smoother. However, with a low frequency there are less switches and therefore fewer switching losses. Also with most motors lower frequencies enable higher torque.

If you have no idea what all this means, just ignore this function and use the default frequency, it will very likely work fine.

The default frequency is 15 kHz.

int dc_get_pwm_frequency(DC *dc, uint16_t *ret_frequency)

Returns the PWM frequency (in Hz) as set by dc_set_pwm_frequency().

int dc_get_stack_input_voltage(DC *dc, 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 dc_get_external_input_voltage(DC *dc, 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 DC 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 dc_get_current_consumption(DC *dc, uint16_t *ret_voltage)

Returns the current consumption of the motor in mA.

int dc_set_drive_mode(DC *dc, uint8_t mode)

Sets the drive mode. Possible modes are:

  • 0 = Drive/Brake
  • 1 = Drive/Coast

These modes are different kinds of motor controls.

In Drive/Brake mode, the motor is always either driving or braking. There is no freewheeling. Advantages are: A more linear correlation between PWM and velocity, more exact accelerations and the possibility to drive with slower velocities.

In Drive/Coast mode, the motor is always either driving or freewheeling. Advantages are: Less current consumption and less demands on the motor and driver chip.

The default value is 0 = Drive/Brake.

The following defines are available for this function:

  • DC_DRIVE_MODE_DRIVE_BRAKE = 0
  • DC_DRIVE_MODE_DRIVE_COAST = 1
int dc_get_drive_mode(DC *dc, uint8_t *ret_mode)

Returns the drive mode, as set by dc_set_drive_mode().

The following defines are available for this function:

  • DC_DRIVE_MODE_DRIVE_BRAKE = 0
  • DC_DRIVE_MODE_DRIVE_COAST = 1
int dc_get_api_version(DC *dc, 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 dc_get_response_expected(DC *dc, 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 dc_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 dc_set_response_expected() for the list of function ID defines available for this function.

int dc_set_response_expected(DC *dc, 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:

  • DC_FUNCTION_SET_VELOCITY = 1
  • DC_FUNCTION_SET_ACCELERATION = 4
  • DC_FUNCTION_SET_PWM_FREQUENCY = 6
  • DC_FUNCTION_FULL_BRAKE = 8
  • DC_FUNCTION_ENABLE = 12
  • DC_FUNCTION_DISABLE = 13
  • DC_FUNCTION_SET_MINIMUM_VOLTAGE = 15
  • DC_FUNCTION_SET_DRIVE_MODE = 17
  • DC_FUNCTION_SET_CURRENT_VELOCITY_PERIOD = 19
  • DC_FUNCTION_SET_SPITFP_BAUDRATE_CONFIG = 231
  • DC_FUNCTION_SET_SPITFP_BAUDRATE = 234
  • DC_FUNCTION_ENABLE_STATUS_LED = 238
  • DC_FUNCTION_DISABLE_STATUS_LED = 239
  • DC_FUNCTION_RESET = 243
int dc_set_response_expected_all(DC *dc, bool response_expected)

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

int dc_set_spitfp_baudrate_config(DC *dc, 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 dc_set_spitfp_baudrate(). If the dynamic baudrate is disabled, the baudrate as set by dc_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 2.3.5 (Firmware).

int dc_get_spitfp_baudrate_config(DC *dc, bool *ret_enable_dynamic_baudrate, uint32_t *ret_minimum_dynamic_baudrate)

Returns the baudrate config, see dc_set_spitfp_baudrate_config().

New in version 2.3.5 (Firmware).

int dc_get_send_timeout_count(DC *dc, 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:

  • DC_COMMUNICATION_METHOD_NONE = 0
  • DC_COMMUNICATION_METHOD_USB = 1
  • DC_COMMUNICATION_METHOD_SPI_STACK = 2
  • DC_COMMUNICATION_METHOD_CHIBI = 3
  • DC_COMMUNICATION_METHOD_RS485 = 4
  • DC_COMMUNICATION_METHOD_WIFI = 5
  • DC_COMMUNICATION_METHOD_ETHERNET = 6
  • DC_COMMUNICATION_METHOD_WIFI_V2 = 7

New in version 2.3.3 (Firmware).

int dc_set_spitfp_baudrate(DC *dc, 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 dc_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 dc_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 dc_get_spitfp_baudrate(DC *dc, char bricklet_port, uint32_t *ret_baudrate)

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

New in version 2.3.3 (Firmware).

int dc_get_spitfp_error_count(DC *dc, 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 dc_enable_status_led(DC *dc)

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 dc_disable_status_led(DC *dc)

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 dc_is_status_led_enabled(DC *dc, bool *ret_enabled)

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

New in version 2.3.1 (Firmware).

int dc_get_protocol1_bricklet_name(DC *dc, 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 dc_get_chip_temperature(DC *dc, 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 dc_reset(DC *dc)

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 dc_get_identity(DC *dc, 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 dc_register_callback(DC *dc, 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 dc_set_minimum_voltage(DC *dc, uint16_t voltage)

Sets the minimum voltage in mV, below which the DC_CALLBACK_UNDER_VOLTAGE callback is triggered. The minimum possible value that works with the DC Brick is 6V. You can use this function to detect the discharge of a battery that is used to drive the motor. If you have a fixed power supply, you likely do not need this functionality.

The default value is 6V.

int dc_get_minimum_voltage(DC *dc, uint16_t *ret_voltage)

Returns the minimum voltage as set by dc_set_minimum_voltage()

int dc_set_current_velocity_period(DC *dc, uint16_t period)

Sets a period in ms with which the DC_CALLBACK_CURRENT_VELOCITY callback is triggered. A period of 0 turns the callback off.

The default value is 0.

int dc_get_current_velocity_period(DC *dc, uint16_t *ret_period)

Returns the period as set by dc_set_current_velocity_period().

Callbacks

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

dc_register_callback(&dc, DC_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.

DC_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 dc_set_minimum_voltage(). The parameter is the current voltage given in mV.

DC_CALLBACK_EMERGENCY_SHUTDOWN
void callback(void *user_data)

This callback is triggered if either the current consumption is too high (above 5A) or the temperature of the driver chip is too high (above 175°C). These two possibilities are essentially the same, since the temperature will reach this threshold immediately if the motor consumes too much current. In case of a voltage below 3.3V (external or stack) this callback is triggered as well.

If this callback is triggered, the driver chip gets disabled at the same time. That means, dc_enable() has to be called to drive the motor again.

Note

This callback only works in Drive/Brake mode (see dc_set_drive_mode()). In Drive/Coast mode it is unfortunately impossible to reliably read the overcurrent/overtemperature signal from the driver chip.

DC_CALLBACK_VELOCITY_REACHED
void callback(int16_t velocity, void *user_data)

This callback is triggered whenever a set velocity is reached. For example: If a velocity of 0 is present, acceleration is set to 5000 and velocity to 10000, the DC_CALLBACK_VELOCITY_REACHED callback will be triggered after about 2 seconds, when the set velocity is actually reached.

Note

Since we can't get any feedback from the DC motor, this only works if the acceleration (see dc_set_acceleration()) 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.

DC_CALLBACK_CURRENT_VELOCITY
void callback(int16_t velocity, void *user_data)

This callback is triggered with the period that is set by dc_set_current_velocity_period(). The parameter is the current velocity used by the motor.

The DC_CALLBACK_CURRENT_VELOCITY callback is only triggered after the set period if there is a change in the velocity.

Constants

DC_DEVICE_IDENTIFIER

This constant is used to identify a DC Brick.

The dc_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.

DC_DEVICE_DISPLAY_NAME

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