Software / API Bindings / C/C++ for Microcontrollers / API Reference and Examples / Bricks / HAT Zero Brick

C/C++ for Microcontrollers - HAT Zero Brick¶

This is the description of the C/C++ for Microcontrollers API bindings for the HAT Zero Brick. General information and technical specifications for the HAT Zero Brick are summarized in its hardware description.

An installation guide for the C/C++ for Microcontrollers API bindings is part of their general description.

Examples¶

The example code below is Public Domain (CC0 1.0).

Simple¶

Download (example_simple.c)

// This example is not self-contained.
// It requires usage of the example driver specific to your platform.
// See the HAL documentation.

#include "src/bindings/hal_common.h"
#include "src/bindings/brick_hat_zero.h"

void check(int rc, const char *msg);
void example_setup(TF_HAL *hal);
void example_loop(TF_HAL *hal);

static TF_HATZero hz;

void example_setup(TF_HAL *hal) {
    // Create device object
    check(tf_hat_zero_create(&hz, NULL, hal), "create device object");

    // Get current voltage
    uint16_t voltage;
    check(tf_hat_zero_get_usb_voltage(&hz, &voltage), "get voltage");

    tf_hal_printf("Voltage: %d 1/%d V\n", voltage, 1000);
}

void example_loop(TF_HAL *hal) {
    // Poll for callbacks
    tf_hal_callback_tick(hal, 0);
}

API¶

Most functions of the C/C++ bindings for microcontrollers return an error code (e_code).

Possible error codes are:

TF_E_OK = 0
TF_E_TIMEOUT = -1
TF_E_INVALID_PARAMETER = -2
TF_E_NOT_SUPPORTED = -3
TF_E_UNKNOWN_ERROR_CODE = -4
TF_E_STREAM_OUT_OF_SYNC = -5
TF_E_INVALID_CHAR_IN_UID = -6
TF_E_UID_TOO_LONG = -7
TF_E_UID_OVERFLOW = -8
TF_E_TOO_MANY_DEVICES = -9
TF_E_DEVICE_NOT_FOUND = -10
TF_E_WRONG_DEVICE_TYPE = -11
TF_E_LOCKED = -12
TF_E_PORT_NOT_FOUND = -13

(as defined in errors.h) as well as the errors returned from the hardware abstraction layer (HAL) that is used.

Use :cpp:func`tf_hal_strerror` (defined in the HAL's header file) to get an error string for 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. The bindings will not write to an output parameter if NULL or nullptr is passed. This can be used to ignore outputs that you are not interested in.

None of the functions listed below are thread-safe. See the API bindings description for details.

Basic Functions¶

int tf_hat_zero_create(TF_HATZero *hat_zero, const char *uid_or_port_name, TF_HAL *hal)¶

Parameters:	hat_zero – Type: TF_HATZero * uid – Type: const char * hal – Type: TF_HAL *
Returns:	e_code – Type: int

Creates the device object hat_zero with the optional unique device ID or port name uid_or_port_name and adds it to the HAL hal:

TF_HATZero hat_zero;
tf_hat_zero_create(&hat_zero, NULL, &hal);

Normally uid_or_port_name can stay NULL. For more details about this see section UID or Port Name.

int tf_hat_zero_destroy(TF_HATZero *hat_zero)¶

Parameters:	hat_zero – Type: TF_HATZero *
Returns:	e_code – Type: int

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

int tf_hat_zero_get_usb_voltage(TF_HATZero *hat_zero, uint16_t *ret_voltage)¶

Parameters:	hat_zero – Type: TF_HATZero *
Output Parameters:	ret_voltage – Type: uint16_t, Unit: 1 mV, Range: [0 to 2¹⁶ - 1]
Returns:	e_code – Type: int

Returns the USB supply voltage of the Raspberry Pi.

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

Advanced Functions¶

int tf_hat_zero_get_spitfp_error_count(TF_HATZero *hat_zero, 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_zero – Type: TF_HATZero *
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:	e_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 tf_hat_zero_set_status_led_config(TF_HATZero *hat_zero, uint8_t config)¶

Parameters:	hat_zero – Type: TF_HATZero * config – Type: uint8_t, Range: See constants, Default: 3
Returns:	e_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:

TF_HAT_ZERO_STATUS_LED_CONFIG_OFF = 0
TF_HAT_ZERO_STATUS_LED_CONFIG_ON = 1
TF_HAT_ZERO_STATUS_LED_CONFIG_SHOW_HEARTBEAT = 2
TF_HAT_ZERO_STATUS_LED_CONFIG_SHOW_STATUS = 3

int tf_hat_zero_get_status_led_config(TF_HATZero *hat_zero, uint8_t *ret_config)¶

Parameters:	hat_zero – Type: TF_HATZero *
Output Parameters:	ret_config – Type: uint8_t, Range: See constants, Default: 3
Returns:	e_code – Type: int

Returns the configuration as set by tf_hat_zero_set_status_led_config()

The following constants are available for this function:

For ret_config:

TF_HAT_ZERO_STATUS_LED_CONFIG_OFF = 0
TF_HAT_ZERO_STATUS_LED_CONFIG_ON = 1
TF_HAT_ZERO_STATUS_LED_CONFIG_SHOW_HEARTBEAT = 2
TF_HAT_ZERO_STATUS_LED_CONFIG_SHOW_STATUS = 3

int tf_hat_zero_get_chip_temperature(TF_HATZero *hat_zero, int16_t *ret_temperature)¶

Parameters:	hat_zero – Type: TF_HATZero *
Output Parameters:	ret_temperature – Type: int16_t, Unit: 1 °C, Range: [-2¹⁵ to 2¹⁵ - 1]
Returns:	e_code – Type: int

Returns the temperature 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 tf_hat_zero_reset(TF_HATZero *hat_zero)¶

Parameters:	hat_zero – Type: TF_HATZero *
Returns:	e_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 tf_hat_zero_get_identity(TF_HATZero *hat_zero, 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_zero – Type: TF_HATZero *
Output Parameters:	ret_uid – Type: char[8] ret_connected_uid – Type: char[8] ret_position – Type: char, Range: ['i'] ret_hardware_version – Type: uint8_t[3] 0: major – Type: uint8_t, Range: [0 to 255] 1: minor – Type: uint8_t, Range: [0 to 255] 2: revision – Type: uint8_t, Range: [0 to 255] ret_firmware_version – Type: uint8_t[3] 0: major – Type: uint8_t, Range: [0 to 255] 1: minor – Type: uint8_t, Range: [0 to 255] 2: revision – Type: uint8_t, Range: [0 to 255] ret_device_identifier – Type: uint16_t, Range: [0 to 2¹⁶ - 1]
Returns:	e_code – Type: int

Returns the UID, the UID where the HAT is connected to (typically '0' as the HAT is the root device in the topology), the position, the hardware and firmware version as well as the device identifier.

The HAT (Zero) Brick is always at position 'i'.

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

Callback Configuration Functions¶

int tf_hat_zero_set_usb_voltage_callback_configuration(TF_HATZero *hat_zero, uint32_t period, bool value_has_to_change, char option, uint16_t min, uint16_t max)¶

Parameters:	hat_zero – Type: TF_HATZero * period – Type: uint32_t, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0 value_has_to_change – Type: bool, Default: false option – Type: char, Range: See constants, Default: 'x' min – Type: uint16_t, Unit: 1 mV, Range: [0 to 2¹⁶ - 1], Default: 0 max – Type: uint16_t, Unit: 1 mV, Range: [0 to 2¹⁶ - 1], Default: 0
Returns:	e_code – Type: int

The period is the period with which the USB Voltage 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 USB Voltage 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 following constants are available for this function:

For option:

TF_HAT_ZERO_THRESHOLD_OPTION_OFF = 'x'
TF_HAT_ZERO_THRESHOLD_OPTION_OUTSIDE = 'o'
TF_HAT_ZERO_THRESHOLD_OPTION_INSIDE = 'i'
TF_HAT_ZERO_THRESHOLD_OPTION_SMALLER = '<'
TF_HAT_ZERO_THRESHOLD_OPTION_GREATER = '>'

New in version 2.0.1 (Firmware).

int tf_hat_zero_get_usb_voltage_callback_configuration(TF_HATZero *hat_zero, uint32_t *ret_period, bool *ret_value_has_to_change, char *ret_option, uint16_t *ret_min, uint16_t *ret_max)¶

Parameters:	hat_zero – Type: TF_HATZero *
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 ret_option – Type: char, Range: See constants, Default: 'x' ret_min – Type: uint16_t, Unit: 1 mV, Range: [0 to 2¹⁶ - 1], Default: 0 ret_max – Type: uint16_t, Unit: 1 mV, Range: [0 to 2¹⁶ - 1], Default: 0
Returns:	e_code – Type: int

Returns the callback configuration as set by tf_hat_zero_set_usb_voltage_callback_configuration().

The following constants are available for this function:

For ret_option:

TF_HAT_ZERO_THRESHOLD_OPTION_OFF = 'x'
TF_HAT_ZERO_THRESHOLD_OPTION_OUTSIDE = 'o'
TF_HAT_ZERO_THRESHOLD_OPTION_INSIDE = 'i'
TF_HAT_ZERO_THRESHOLD_OPTION_SMALLER = '<'
TF_HAT_ZERO_THRESHOLD_OPTION_GREATER = '>'

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 corresponding tf_hat_zero_register_*_callback function. The user_data passed to the registration function as well as the device that triggered the callback are passed to the registered callback handler.

Only one handler can be registered to a callback at the same time. To deregister a callback, call the tf_hat_zero_register_*_callback function with NULL as handler.

Note

Using callbacks for recurring events is preferred compared to using getters. Polling for a callback requires writing one byte only. See here Optimizing Performance.

Warning

Calling bindings function from inside a callback handler is not allowed. See here Thread safety.

int tf_hat_zero_register_usb_voltage_callback(TF_HATZero *hat_zero, TF_HATZero_USBVoltageHandler handler, void *user_data)¶

void handler(TF_HATZero *hat_zero, uint16_t voltage, void *user_data)

Callback Parameters:	hat_zero – Type: TF_HATZero * voltage – Type: uint16_t, Unit: 1 mV, Range: [0 to 2¹⁶ - 1] user_data – Type: void *

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

The parameter is the same as tf_hat_zero_get_usb_voltage().

New in version 2.0.1 (Firmware).

Virtual Functions¶

Virtual functions don't communicate with the device itself, but operate only on the API bindings device object.

int tf_hat_zero_get_response_expected(TF_HATZero *hat_zero, uint8_t function_id, bool *ret_response_expected)¶

Parameters:	hat_zero – Type: TF_HATZero * function_id – Type: uint8_t, Range: See constants
Output Parameters:	ret_response_expected – Type: bool
Returns:	e_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 tf_hat_zero_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 sent and errors are silently ignored, because they cannot be detected.

The following constants are available for this function:

For function_id:

TF_HAT_ZERO_FUNCTION_SET_USB_VOLTAGE_CALLBACK_CONFIGURATION = 2
TF_HAT_ZERO_FUNCTION_SET_WRITE_FIRMWARE_POINTER = 237
TF_HAT_ZERO_FUNCTION_SET_STATUS_LED_CONFIG = 239
TF_HAT_ZERO_FUNCTION_RESET = 243
TF_HAT_ZERO_FUNCTION_WRITE_UID = 248

int tf_hat_zero_set_response_expected(TF_HATZero *hat_zero, uint8_t function_id, bool response_expected)¶

Parameters:	hat_zero – Type: TF_HATZero * function_id – Type: uint8_t, Range: See constants response_expected – Type: bool
Returns:	e_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.

The following constants are available for this function:

For function_id:

TF_HAT_ZERO_FUNCTION_SET_USB_VOLTAGE_CALLBACK_CONFIGURATION = 2
TF_HAT_ZERO_FUNCTION_SET_WRITE_FIRMWARE_POINTER = 237
TF_HAT_ZERO_FUNCTION_SET_STATUS_LED_CONFIG = 239
TF_HAT_ZERO_FUNCTION_RESET = 243
TF_HAT_ZERO_FUNCTION_WRITE_UID = 248

int tf_hat_zero_set_response_expected_all(TF_HATZero *hat_zero, bool response_expected)¶

Parameters:	hat_zero – Type: TF_HATZero * response_expected – Type: bool
Returns:	e_code – Type: int

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

Internal Functions¶

Internal functions are used for maintenance tasks such as flashing a new firmware of changing the UID of a Bricklet. These task should be performed using Brick Viewer instead of using the internal functions directly.

int tf_hat_zero_set_bootloader_mode(TF_HATZero *hat_zero, uint8_t mode, uint8_t *ret_status)¶

Parameters:	hat_zero – Type: TF_HATZero * mode – Type: uint8_t, Range: See constants
Output Parameters:	ret_status – Type: uint8_t, Range: See constants
Returns:	e_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:

TF_HAT_ZERO_BOOTLOADER_MODE_BOOTLOADER = 0
TF_HAT_ZERO_BOOTLOADER_MODE_FIRMWARE = 1
TF_HAT_ZERO_BOOTLOADER_MODE_BOOTLOADER_WAIT_FOR_REBOOT = 2
TF_HAT_ZERO_BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_REBOOT = 3
TF_HAT_ZERO_BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_ERASE_AND_REBOOT = 4

For ret_status:

TF_HAT_ZERO_BOOTLOADER_STATUS_OK = 0
TF_HAT_ZERO_BOOTLOADER_STATUS_INVALID_MODE = 1
TF_HAT_ZERO_BOOTLOADER_STATUS_NO_CHANGE = 2
TF_HAT_ZERO_BOOTLOADER_STATUS_ENTRY_FUNCTION_NOT_PRESENT = 3
TF_HAT_ZERO_BOOTLOADER_STATUS_DEVICE_IDENTIFIER_INCORRECT = 4
TF_HAT_ZERO_BOOTLOADER_STATUS_CRC_MISMATCH = 5

int tf_hat_zero_get_bootloader_mode(TF_HATZero *hat_zero, uint8_t *ret_mode)¶

Parameters:	hat_zero – Type: TF_HATZero *
Output Parameters:	ret_mode – Type: uint8_t, Range: See constants
Returns:	e_code – Type: int

Returns the current bootloader mode, see tf_hat_zero_set_bootloader_mode().

The following constants are available for this function:

For ret_mode:

TF_HAT_ZERO_BOOTLOADER_MODE_BOOTLOADER = 0
TF_HAT_ZERO_BOOTLOADER_MODE_FIRMWARE = 1
TF_HAT_ZERO_BOOTLOADER_MODE_BOOTLOADER_WAIT_FOR_REBOOT = 2
TF_HAT_ZERO_BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_REBOOT = 3
TF_HAT_ZERO_BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_ERASE_AND_REBOOT = 4

int tf_hat_zero_set_write_firmware_pointer(TF_HATZero *hat_zero, uint32_t pointer)¶

Parameters:	hat_zero – Type: TF_HATZero * pointer – Type: uint32_t, Unit: 1 B, Range: [0 to 2³² - 1]
Returns:	e_code – Type: int

Sets the firmware pointer for tf_hat_zero_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 tf_hat_zero_write_firmware(TF_HATZero *hat_zero, const uint8_t data[64], uint8_t *ret_status)¶

Parameters:	hat_zero – Type: TF_HATZero * data – Type: const uint8_t[64], Range: [0 to 255]
Output Parameters:	ret_status – Type: uint8_t, Range: [0 to 255]
Returns:	e_code – Type: int

Writes 64 Bytes of firmware at the position as written by tf_hat_zero_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 tf_hat_zero_write_uid(TF_HATZero *hat_zero, uint32_t uid)¶

Parameters:	hat_zero – Type: TF_HATZero * uid – Type: uint32_t, Range: [0 to 2³² - 1]
Returns:	e_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 tf_hat_zero_read_uid(TF_HATZero *hat_zero, uint32_t *ret_uid)¶

Parameters:	hat_zero – Type: TF_HATZero *
Output Parameters:	ret_uid – Type: uint32_t, Range: [0 to 2³² - 1]
Returns:	e_code – Type: int

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

Constants¶

TF_HAT_ZERO_DEVICE_IDENTIFIER¶

This constant is used to identify a HAT Zero Brick.

The functions tf_hat_zero_get_identity() and tf_hal_get_device_info() have a device_identifier output parameter to specify the Brick's or Bricklet's type.

TF_HAT_ZERO_DEVICE_DISPLAY_NAME¶: This constant represents the human readable name of a HAT Zero Brick.