C/C++ - HAT Zero Brick

This is the description of the C/C++ 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++ API bindings is part of their general description.

Examples

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

Simple

Download (example_simple.c)

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
#include <stdio.h>

#include "ip_connection.h"
#include "brick_hat_zero.h"

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

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

    // Create device object
    HATZero hz;
    hat_zero_create(&hz, 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 voltage
    uint16_t voltage;
    if(hat_zero_get_usb_voltage(&hz, &voltage) < 0) {
        fprintf(stderr, "Could not get voltage, probably timeout\n");
        return 1;
    }

    printf("Voltage: %f V\n", voltage/1000.0);

    printf("Press key to exit\n");
    getchar();
    hat_zero_destroy(&hz);
    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 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_zero_create(HATZero *hat_zero, const char *uid, IPConnection *ipcon)

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

HATZero hat_zero;
hat_zero_create(&hat_zero, "YOUR_DEVICE_UID", &ipcon);

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

void hat_zero_destroy(HATZero *hat_zero)

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

int hat_zero_get_usb_voltage(HATZero *hat_zero, uint16_t *ret_voltage)

Returns the USB supply voltage of the Raspberry Pi in mV.

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

Advanced Functions

int hat_zero_get_api_version(HATZero *hat_zero, 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 hat_zero_get_response_expected(HATZero *hat_zero, 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 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 send and errors are silently ignored, because they cannot be detected.

The following constants are available for this function:

  • HAT_ZERO_FUNCTION_SET_USB_VOLTAGE_CALLBACK_CONFIGURATION = 2
  • HAT_ZERO_FUNCTION_SET_WRITE_FIRMWARE_POINTER = 237
  • HAT_ZERO_FUNCTION_SET_STATUS_LED_CONFIG = 239
  • HAT_ZERO_FUNCTION_RESET = 243
  • HAT_ZERO_FUNCTION_WRITE_UID = 248
int hat_zero_set_response_expected(HATZero *hat_zero, 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 constants are available for this function:

  • HAT_ZERO_FUNCTION_SET_USB_VOLTAGE_CALLBACK_CONFIGURATION = 2
  • HAT_ZERO_FUNCTION_SET_WRITE_FIRMWARE_POINTER = 237
  • HAT_ZERO_FUNCTION_SET_STATUS_LED_CONFIG = 239
  • HAT_ZERO_FUNCTION_RESET = 243
  • HAT_ZERO_FUNCTION_WRITE_UID = 248
int hat_zero_set_response_expected_all(HATZero *hat_zero, bool response_expected)

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

int hat_zero_get_spitfp_error_count(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)

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_zero_set_bootloader_mode(HATZero *hat_zero, 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 constants are available for this function:

  • HAT_ZERO_BOOTLOADER_MODE_BOOTLOADER = 0
  • HAT_ZERO_BOOTLOADER_MODE_FIRMWARE = 1
  • HAT_ZERO_BOOTLOADER_MODE_BOOTLOADER_WAIT_FOR_REBOOT = 2
  • HAT_ZERO_BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_REBOOT = 3
  • HAT_ZERO_BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_ERASE_AND_REBOOT = 4
  • HAT_ZERO_BOOTLOADER_STATUS_OK = 0
  • HAT_ZERO_BOOTLOADER_STATUS_INVALID_MODE = 1
  • HAT_ZERO_BOOTLOADER_STATUS_NO_CHANGE = 2
  • HAT_ZERO_BOOTLOADER_STATUS_ENTRY_FUNCTION_NOT_PRESENT = 3
  • HAT_ZERO_BOOTLOADER_STATUS_DEVICE_IDENTIFIER_INCORRECT = 4
  • HAT_ZERO_BOOTLOADER_STATUS_CRC_MISMATCH = 5
int hat_zero_get_bootloader_mode(HATZero *hat_zero, uint8_t *ret_mode)

Returns the current bootloader mode, see hat_zero_set_bootloader_mode().

The following constants are available for this function:

  • HAT_ZERO_BOOTLOADER_MODE_BOOTLOADER = 0
  • HAT_ZERO_BOOTLOADER_MODE_FIRMWARE = 1
  • HAT_ZERO_BOOTLOADER_MODE_BOOTLOADER_WAIT_FOR_REBOOT = 2
  • HAT_ZERO_BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_REBOOT = 3
  • HAT_ZERO_BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_ERASE_AND_REBOOT = 4
int hat_zero_set_write_firmware_pointer(HATZero *hat_zero, uint32_t pointer)

Sets the firmware pointer for 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 hat_zero_write_firmware(HATZero *hat_zero, uint8_t data[64], uint8_t *ret_status)

Writes 64 Bytes of firmware at the position as written by 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 hat_zero_set_status_led_config(HATZero *hat_zero, 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 constants are available for this function:

  • HAT_ZERO_STATUS_LED_CONFIG_OFF = 0
  • HAT_ZERO_STATUS_LED_CONFIG_ON = 1
  • HAT_ZERO_STATUS_LED_CONFIG_SHOW_HEARTBEAT = 2
  • HAT_ZERO_STATUS_LED_CONFIG_SHOW_STATUS = 3
int hat_zero_get_status_led_config(HATZero *hat_zero, uint8_t *ret_config)

Returns the configuration as set by hat_zero_set_status_led_config()

The following constants are available for this function:

  • HAT_ZERO_STATUS_LED_CONFIG_OFF = 0
  • HAT_ZERO_STATUS_LED_CONFIG_ON = 1
  • HAT_ZERO_STATUS_LED_CONFIG_SHOW_HEARTBEAT = 2
  • HAT_ZERO_STATUS_LED_CONFIG_SHOW_STATUS = 3
int hat_zero_get_chip_temperature(HATZero *hat_zero, 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 hat_zero_reset(HATZero *hat_zero)

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_zero_write_uid(HATZero *hat_zero, 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 hat_zero_read_uid(HATZero *hat_zero, uint32_t *ret_uid)

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

int hat_zero_get_identity(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)

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_zero_register_callback(HATZero *hat_zero, int16_t callback_id, void (*function)(void), 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 hat_zero_set_usb_voltage_callback_configuration(HATZero *hat_zero, uint32_t period, bool value_has_to_change, char option, uint16_t min, uint16_t max)

The period in ms is the period with which the HAT_ZERO_CALLBACK_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 HAT_ZERO_CALLBACK_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 default value is (0, false, 'x', 0, 0).

The following constants are available for this function:

  • HAT_ZERO_THRESHOLD_OPTION_OFF = 'x'
  • HAT_ZERO_THRESHOLD_OPTION_OUTSIDE = 'o'
  • HAT_ZERO_THRESHOLD_OPTION_INSIDE = 'i'
  • HAT_ZERO_THRESHOLD_OPTION_SMALLER = '<'
  • HAT_ZERO_THRESHOLD_OPTION_GREATER = '>'

New in version 2.0.1 (Firmware).

int hat_zero_get_usb_voltage_callback_configuration(HATZero *hat_zero, uint32_t *ret_period, bool *ret_value_has_to_change, char *ret_option, uint16_t *ret_min, uint16_t *ret_max)

Returns the callback configuration as set by hat_zero_set_usb_voltage_callback_configuration().

The following constants are available for this function:

  • HAT_ZERO_THRESHOLD_OPTION_OFF = 'x'
  • HAT_ZERO_THRESHOLD_OPTION_OUTSIDE = 'o'
  • HAT_ZERO_THRESHOLD_OPTION_INSIDE = 'i'
  • HAT_ZERO_THRESHOLD_OPTION_SMALLER = '<'
  • 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 hat_zero_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);
}

hat_zero_register_callback(&hat_zero, HAT_ZERO_CALLBACK_EXAMPLE, (void (*)(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.

HAT_ZERO_CALLBACK_USB_VOLTAGE
void callback(uint16_t voltage, void *user_data)

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

The parameter is the same as hat_zero_get_usb_voltage().

New in version 2.0.1 (Firmware).

Constants

HAT_ZERO_DEVICE_IDENTIFIER

This constant is used to identify a HAT Zero Brick.

The hat_zero_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_ZERO_DEVICE_DISPLAY_NAME

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