C/C++ - HAT Brick

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

Sleep

Download (example_sleep.c)

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#include <stdio.h>

#include "ip_connection.h"
#include "brick_hat.h"

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

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

    // Create device object
    HAT hat;
    hat_create(&hat, 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

    // Turn Raspberry Pi and Bricklets off in 2 seconds for 30 minutes with sleep indicator enabled
    hat_set_sleep_mode(&hat, 2, 1800, true, true, true);

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

API

Every function of the C/C++ bindings returns an integer which describes an error code. Data returned from the device, when a getter is called, is handled via output parameters. These parameters are labeled with the ret_ prefix.

Possible error codes are:

  • E_OK = 0
  • E_TIMEOUT = -1
  • E_NO_STREAM_SOCKET = -2
  • E_HOSTNAME_INVALID = -3
  • E_NO_CONNECT = -4
  • E_NO_THREAD = -5
  • E_NOT_ADDED = -6 (unused since C/C++ bindings version 2.0.0)
  • E_ALREADY_CONNECTED = -7
  • E_NOT_CONNECTED = -8
  • E_INVALID_PARAMETER = -9
  • E_NOT_SUPPORTED = -10
  • E_UNKNOWN_ERROR_CODE = -11
  • E_STREAM_OUT_OF_SYNC = -12
  • E_INVALID_UID = -13
  • E_NON_ASCII_CHAR_IN_SECRET = -14

as defined in ip_connection.h.

All functions listed below are thread-safe.

Basic Functions

void hat_create(HAT *hat, const char *uid, IPConnection *ipcon)
Parameters:
  • hat – Type: HAT *
  • uid – Type: const char *
  • ipcon – Type: IPConnection *

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

HAT hat;
hat_create(&hat, "YOUR_DEVICE_UID", &ipcon);

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

void hat_destroy(HAT *hat)
Parameters:
  • hat – Type: HAT *

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

int hat_set_sleep_mode(HAT *hat, uint32_t power_off_delay, uint32_t power_off_duration, bool raspberry_pi_off, bool bricklets_off, bool enable_sleep_indicator)
Parameters:
  • hat – Type: HAT *
  • power_off_delay – Type: uint32_t, Range: [0 to 232 - 1]
  • power_off_duration – Type: uint32_t, Range: [0 to 232 - 1]
  • raspberry_pi_off – Type: bool
  • bricklets_off – Type: bool
  • enable_sleep_indicator – Type: bool
Returns:
  • error_code – Type: int

Sets the sleep mode.

Note

Calling this function will cut the Raspberry Pi's power after Power Off Delay seconds. You have to shut down the operating system yourself, e.g. by calling 'sudo shutdown -h now'.

Parameters:

  • Power Off Delay: Time in seconds before the RPi/Bricklets are powered off.
  • Power Off Duration: Duration in seconds that the RPi/Bricklets stay powered off.
  • Raspberry Pi Off: RPi is powered off if set to true.
  • Bricklets Off: Bricklets are powered off if set to true.
  • Enable Sleep Indicator: If set to true, the status LED will blink in a 1s interval during the whole power off duration. This will draw additional 0.3mA.

Example: To turn RPi and Bricklets off in 5 seconds for 10 minutes with sleep indicator enabled, call (5, 60*10, true, true, true).

This function can also be used to implement a watchdog. To do this you can write a program that calls this function once per second in a loop with (10, 2, true, false, false). If the RPi crashes or gets stuck the HAT will reset the RPi after 10 seconds.

int hat_get_sleep_mode(HAT *hat, uint32_t *ret_power_off_delay, uint32_t *ret_power_off_duration, bool *ret_raspberry_pi_off, bool *ret_bricklets_off, bool *ret_enable_sleep_indicator)
Parameters:
  • hat – Type: HAT *
Output Parameters:
  • ret_power_off_delay – Type: uint32_t, Range: [0 to 232 - 1]
  • ret_power_off_duration – Type: uint32_t, Range: [0 to 232 - 1]
  • ret_raspberry_pi_off – Type: bool
  • ret_bricklets_off – Type: bool
  • ret_enable_sleep_indicator – Type: bool
Returns:
  • error_code – Type: int

Returns the sleep mode settings as set by hat_set_sleep_mode().

int hat_set_bricklet_power(HAT *hat, bool bricklet_power)
Parameters:
  • hat – Type: HAT *
  • bricklet_power – Type: bool
Returns:
  • error_code – Type: int

Set to true/false to turn the power supply of the connected Bricklets on/off.

By default the Bricklets are on.

int hat_get_bricklet_power(HAT *hat, bool *ret_bricklet_power)
Parameters:
  • hat – Type: HAT *
Output Parameters:
  • ret_bricklet_power – Type: bool
Returns:
  • error_code – Type: int

Returns the power status of the connected Bricklets as set by hat_set_bricklet_power().

int hat_get_voltages(HAT *hat, uint16_t *ret_voltage_usb, uint16_t *ret_voltage_dc)
Parameters:
  • hat – Type: HAT *
Output Parameters:
  • ret_voltage_usb – Type: uint16_t, Range: [0 to 216 - 1]
  • ret_voltage_dc – Type: uint16_t, Range: [0 to 216 - 1]
Returns:
  • error_code – Type: int

Returns the USB supply voltage and the DC input supply voltage in mV.

There are three possible combinations:

  • Only USB connected: The USB supply voltage will be fed back to the DC input connector. You will read the USB voltage and a slightly lower voltage on the DC input.
  • Only DC input connected: The DC voltage will not be fed back to the USB connector. You will read the DC input voltage and the USB voltage will be 0.
  • USB and DC input connected: You will read both voltages. In this case the USB supply will be without load, but it will work as backup if you disconnect the DC input (or if the DC input voltage falls below the USB voltage).

Advanced Functions

int hat_get_api_version(HAT *hat, uint8_t ret_api_version[3])
Parameters:
  • hat – Type: HAT *
Output Parameters:
  • ret_api_version – Type: uint8_t[3], Range: [0 to 255]
Returns:
  • error_code – Type: int

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 hat_get_response_expected(HAT *hat, uint8_t function_id, bool *ret_response_expected)
Parameters:
  • hat – Type: HAT *
  • function_id – Type: uint8_t, Range: See constants
Output Parameters:
  • ret_response_expected – Type: bool
Returns:
  • error_code – Type: int

Returns the response expected flag for the function specified by the function ID parameter. It is true if the function is expected to send a response, false otherwise.

For getter functions this is enabled by default and cannot be disabled, because those functions will always send a response. For callback configuration functions it is enabled by default too, but can be disabled by hat_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.

The following constants are available for this function:

For function_id:

  • HAT_FUNCTION_SET_SLEEP_MODE = 1
  • HAT_FUNCTION_SET_BRICKLET_POWER = 3
  • HAT_FUNCTION_SET_VOLTAGES_CALLBACK_CONFIGURATION = 6
  • HAT_FUNCTION_SET_WRITE_FIRMWARE_POINTER = 237
  • HAT_FUNCTION_SET_STATUS_LED_CONFIG = 239
  • HAT_FUNCTION_RESET = 243
  • HAT_FUNCTION_WRITE_UID = 248
int hat_set_response_expected(HAT *hat, uint8_t function_id, bool response_expected)
Parameters:
  • hat – Type: HAT *
  • function_id – Type: uint8_t, Range: See constants
  • response_expected – Type: bool
Returns:
  • error_code – Type: int

Changes the response expected flag of the function specified by the function ID parameter. This flag can only be changed for setter (default value: false) and callback configuration functions (default value: true). For getter functions it is always enabled.

Enabling the response expected flag for a setter function allows to detect timeouts and other error conditions calls of this setter as well. The device will then send a response for this purpose. If this flag is disabled for a setter function then no response is send and errors are silently ignored, because they cannot be detected.

The following constants are available for this function:

For function_id:

  • HAT_FUNCTION_SET_SLEEP_MODE = 1
  • HAT_FUNCTION_SET_BRICKLET_POWER = 3
  • HAT_FUNCTION_SET_VOLTAGES_CALLBACK_CONFIGURATION = 6
  • HAT_FUNCTION_SET_WRITE_FIRMWARE_POINTER = 237
  • HAT_FUNCTION_SET_STATUS_LED_CONFIG = 239
  • HAT_FUNCTION_RESET = 243
  • HAT_FUNCTION_WRITE_UID = 248
int hat_set_response_expected_all(HAT *hat, bool response_expected)
Parameters:
  • hat – Type: HAT *
  • response_expected – Type: bool
Returns:
  • error_code – Type: int

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

int hat_get_spitfp_error_count(HAT *hat, 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)
Parameters:
  • hat – Type: HAT *
Output Parameters:
  • ret_error_count_ack_checksum – Type: uint32_t, Range: [0 to 232 - 1]
  • ret_error_count_message_checksum – Type: uint32_t, Range: [0 to 232 - 1]
  • ret_error_count_frame – Type: uint32_t, Range: [0 to 232 - 1]
  • ret_error_count_overflow – Type: uint32_t, Range: [0 to 232 - 1]
Returns:
  • error_code – Type: int

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 hat_set_bootloader_mode(HAT *hat, uint8_t mode, uint8_t *ret_status)
Parameters:
  • hat – Type: HAT *
  • mode – Type: uint8_t, Range: See constants
Output Parameters:
  • ret_status – Type: uint8_t, Range: See constants
Returns:
  • error_code – Type: int

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 constants are available for this function:

For mode:

  • HAT_BOOTLOADER_MODE_BOOTLOADER = 0
  • HAT_BOOTLOADER_MODE_FIRMWARE = 1
  • HAT_BOOTLOADER_MODE_BOOTLOADER_WAIT_FOR_REBOOT = 2
  • HAT_BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_REBOOT = 3
  • HAT_BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_ERASE_AND_REBOOT = 4

For ret_status:

  • HAT_BOOTLOADER_STATUS_OK = 0
  • HAT_BOOTLOADER_STATUS_INVALID_MODE = 1
  • HAT_BOOTLOADER_STATUS_NO_CHANGE = 2
  • HAT_BOOTLOADER_STATUS_ENTRY_FUNCTION_NOT_PRESENT = 3
  • HAT_BOOTLOADER_STATUS_DEVICE_IDENTIFIER_INCORRECT = 4
  • HAT_BOOTLOADER_STATUS_CRC_MISMATCH = 5
int hat_get_bootloader_mode(HAT *hat, uint8_t *ret_mode)
Parameters:
  • hat – Type: HAT *
Output Parameters:
  • ret_mode – Type: uint8_t, Range: See constants
Returns:
  • error_code – Type: int

Returns the current bootloader mode, see hat_set_bootloader_mode().

The following constants are available for this function:

For ret_mode:

  • HAT_BOOTLOADER_MODE_BOOTLOADER = 0
  • HAT_BOOTLOADER_MODE_FIRMWARE = 1
  • HAT_BOOTLOADER_MODE_BOOTLOADER_WAIT_FOR_REBOOT = 2
  • HAT_BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_REBOOT = 3
  • HAT_BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_ERASE_AND_REBOOT = 4
int hat_set_write_firmware_pointer(HAT *hat, uint32_t pointer)
Parameters:
  • hat – Type: HAT *
  • pointer – Type: uint32_t, Range: [0 to 232 - 1]
Returns:
  • error_code – Type: int

Sets the firmware pointer for hat_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 hat_write_firmware(HAT *hat, uint8_t data[64], uint8_t *ret_status)
Parameters:
  • hat – Type: HAT *
  • data – Type: uint8_t[64], Range: [0 to 255]
Output Parameters:
  • ret_status – Type: uint8_t, Range: [0 to 255]
Returns:
  • error_code – Type: int

Writes 64 Bytes of firmware at the position as written by hat_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 hat_set_status_led_config(HAT *hat, uint8_t config)
Parameters:
  • hat – Type: HAT *
  • config – Type: uint8_t, Range: See constants
Returns:
  • error_code – Type: int

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 constants are available for this function:

For config:

  • HAT_STATUS_LED_CONFIG_OFF = 0
  • HAT_STATUS_LED_CONFIG_ON = 1
  • HAT_STATUS_LED_CONFIG_SHOW_HEARTBEAT = 2
  • HAT_STATUS_LED_CONFIG_SHOW_STATUS = 3
int hat_get_status_led_config(HAT *hat, uint8_t *ret_config)
Parameters:
  • hat – Type: HAT *
Output Parameters:
  • ret_config – Type: uint8_t, Range: See constants
Returns:
  • error_code – Type: int

Returns the configuration as set by hat_set_status_led_config()

The following constants are available for this function:

For ret_config:

  • HAT_STATUS_LED_CONFIG_OFF = 0
  • HAT_STATUS_LED_CONFIG_ON = 1
  • HAT_STATUS_LED_CONFIG_SHOW_HEARTBEAT = 2
  • HAT_STATUS_LED_CONFIG_SHOW_STATUS = 3
int hat_get_chip_temperature(HAT *hat, int16_t *ret_temperature)
Parameters:
  • hat – Type: HAT *
Output Parameters:
  • ret_temperature – Type: int16_t, Range: [-215 to 215 - 1]
Returns:
  • error_code – Type: int

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 hat_reset(HAT *hat)
Parameters:
  • hat – Type: HAT *
Returns:
  • error_code – Type: int

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 hat_write_uid(HAT *hat, uint32_t uid)
Parameters:
  • hat – Type: HAT *
  • uid – Type: uint32_t, Range: [0 to 232 - 1]
Returns:
  • error_code – Type: int

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 hat_read_uid(HAT *hat, uint32_t *ret_uid)
Parameters:
  • hat – Type: HAT *
Output Parameters:
  • ret_uid – Type: uint32_t, Range: [0 to 232 - 1]
Returns:
  • error_code – Type: int

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

int hat_get_identity(HAT *hat, char ret_uid[8], char ret_connected_uid[8], char *ret_position, uint8_t ret_hardware_version[3], uint8_t ret_firmware_version[3], uint16_t *ret_device_identifier)
Parameters:
  • hat – Type: HAT *
Output Parameters:
  • ret_uid – Type: char[8]
  • ret_connected_uid – Type: char[8]
  • ret_position – Type: char
  • ret_hardware_version – Type: uint8_t[3], Range: [0 to 255]
  • ret_firmware_version – Type: uint8_t[3], Range: [0 to 255]
  • ret_device_identifier – Type: uint16_t, Range: [0 to 216 - 1]
Returns:
  • error_code – Type: int

Returns the UID, the UID where the Bricklet is connected to, the position, the hardware and firmware version as well as the device identifier.

The position can be 'a', 'b', 'c' or 'd'.

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

Callback Configuration Functions

void hat_register_callback(HAT *hat, int16_t callback_id, void (*function)(void), void *user_data)
Parameters:
  • hat – Type: HAT *
  • callback_id – Type: int16_t
  • function – Type: void (*)(void)
  • user_data – Type: void *

Registers the given function with the given callback_id. The user_data will be passed as the last parameter to the function.

The available callback IDs with corresponding function signatures are listed below.

int hat_set_voltages_callback_configuration(HAT *hat, uint32_t period, bool value_has_to_change)
Parameters:
  • hat – Type: HAT *
  • period – Type: uint32_t, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0
  • value_has_to_change – Type: bool, Default: false
Returns:
  • error_code – Type: int

The period is the period with which the HAT_CALLBACK_VOLTAGES 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.

New in version 2.0.1 (Firmware).

int hat_get_voltages_callback_configuration(HAT *hat, uint32_t *ret_period, bool *ret_value_has_to_change)
Parameters:
  • hat – Type: HAT *
Output Parameters:
  • ret_period – Type: uint32_t, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0
  • ret_value_has_to_change – Type: bool, Default: false
Returns:
  • error_code – Type: int

Returns the callback configuration as set by hat_set_voltages_callback_configuration().

New in version 2.0.1 (Firmware).

Callbacks

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

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

hat_register_callback(&hat, HAT_CALLBACK_EXAMPLE, (void (*)(void))my_callback, NULL);

The available constants with corresponding function signatures are described below.

Note

Using callbacks for recurring events is always preferred compared to using getters. It will use less USB bandwidth and the latency will be a lot better, since there is no round trip time.

HAT_CALLBACK_VOLTAGES
void callback(uint16_t voltage_usb, uint16_t voltage_dc, void *user_data)
Callback Parameters:
  • voltage_usb – Type: uint16_t, Range: [0 to 216 - 1]
  • voltage_dc – Type: uint16_t, Range: [0 to 216 - 1]
  • user_data – Type: void *

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

The parameters are the same as hat_get_voltages().

New in version 2.0.1 (Firmware).

Constants

HAT_DEVICE_IDENTIFIER

This constant is used to identify a HAT Brick.

The hat_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.

HAT_DEVICE_DISPLAY_NAME

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