C/C++ - Thermocouple Bricklet

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

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#include <stdio.h>

#include "ip_connection.h"
#include "bricklet_thermocouple.h"

#define HOST "localhost"
#define PORT 4223
#define UID "XYZ" // Change XYZ to the UID of your Thermocouple Bricklet

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

    // Create device object
    Thermocouple t;
    thermocouple_create(&t, 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 temperature
    int32_t temperature;
    if(thermocouple_get_temperature(&t, &temperature) < 0) {
        fprintf(stderr, "Could not get temperature, probably timeout\n");
        return 1;
    }

    printf("Temperature: %f °C\n", temperature/100.0);

    printf("Press key to exit\n");
    getchar();
    thermocouple_destroy(&t);
    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 "bricklet_thermocouple.h"

#define HOST "localhost"
#define PORT 4223
#define UID "XYZ" // Change XYZ to the UID of your Thermocouple Bricklet

// Callback function for temperature callback
void cb_temperature(int32_t temperature, void *user_data) {
    (void)user_data; // avoid unused parameter warning

    printf("Temperature: %f °C\n", temperature/100.0);
}

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

    // Create device object
    Thermocouple t;
    thermocouple_create(&t, 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 temperature callback to function cb_temperature
    thermocouple_register_callback(&t,
                                   THERMOCOUPLE_CALLBACK_TEMPERATURE,
                                   (void *)cb_temperature,
                                   NULL);

    // Set period for temperature callback to 1s (1000ms)
    // Note: The temperature callback is only called every second
    //       if the temperature has changed since the last call!
    thermocouple_set_temperature_callback_period(&t, 1000);

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

Threshold

Download (example_threshold.c)

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#include <stdio.h>

#include "ip_connection.h"
#include "bricklet_thermocouple.h"

#define HOST "localhost"
#define PORT 4223
#define UID "XYZ" // Change XYZ to the UID of your Thermocouple Bricklet

// Callback function for temperature reached callback
void cb_temperature_reached(int32_t temperature, void *user_data) {
    (void)user_data; // avoid unused parameter warning

    printf("Temperature: %f °C\n", temperature/100.0);
}

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

    // Create device object
    Thermocouple t;
    thermocouple_create(&t, 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 threshold callbacks with a debounce time of 10 seconds (10000ms)
    thermocouple_set_debounce_period(&t, 10000);

    // Register temperature reached callback to function cb_temperature_reached
    thermocouple_register_callback(&t,
                                   THERMOCOUPLE_CALLBACK_TEMPERATURE_REACHED,
                                   (void *)cb_temperature_reached,
                                   NULL);

    // Configure threshold for temperature "greater than 30 °C"
    thermocouple_set_temperature_callback_threshold(&t, '>', 30*100, 0);

    printf("Press key to exit\n");
    getchar();
    thermocouple_destroy(&t);
    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

as defined in ip_connection.h.

All functions listed below are thread-safe.

Basic Functions

void thermocouple_create(Thermocouple *thermocouple, const char *uid, IPConnection *ipcon)

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

Thermocouple thermocouple;
thermocouple_create(&thermocouple, "YOUR_DEVICE_UID", &ipcon);

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

void thermocouple_destroy(Thermocouple *thermocouple)

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

int thermocouple_get_temperature(Thermocouple *thermocouple, int32_t *ret_temperature)

Returns the temperature of the thermocouple. The value is given in °C/100, e.g. a value of 4223 means that a temperature of 42.23 °C is measured.

If you want to get the temperature periodically, it is recommended to use the THERMOCOUPLE_CALLBACK_TEMPERATURE callback and set the period with thermocouple_set_temperature_callback_period().

Advanced Functions

int thermocouple_set_configuration(Thermocouple *thermocouple, uint8_t averaging, uint8_t thermocouple_type, uint8_t filter)

You can configure averaging size, thermocouple type and frequency filtering.

Available averaging sizes are 1, 2, 4, 8 and 16 samples.

As thermocouple type you can use B, E, J, K, N, R, S and T. If you have a different thermocouple or a custom thermocouple you can also use G8 and G32. With these types the returned value will not be in °C/100, it will be calculated by the following formulas:

  • G8: value = 8 * 1.6 * 2^17 * Vin
  • G32: value = 32 * 1.6 * 2^17 * Vin

where Vin is the thermocouple input voltage.

The frequency filter can be either configured to 50Hz or to 60Hz. You should configure it according to your utility frequency.

The conversion time depends on the averaging and filter configuration, it can be calculated as follows:

  • 60Hz: time = 82 + (samples - 1) * 16.67
  • 50Hz: time = 98 + (samples - 1) * 20

The default configuration is 16 samples, K type and 50Hz.

The following defines are available for this function:

  • THERMOCOUPLE_AVERAGING_1 = 1
  • THERMOCOUPLE_AVERAGING_2 = 2
  • THERMOCOUPLE_AVERAGING_4 = 4
  • THERMOCOUPLE_AVERAGING_8 = 8
  • THERMOCOUPLE_AVERAGING_16 = 16
  • THERMOCOUPLE_TYPE_B = 0
  • THERMOCOUPLE_TYPE_E = 1
  • THERMOCOUPLE_TYPE_J = 2
  • THERMOCOUPLE_TYPE_K = 3
  • THERMOCOUPLE_TYPE_N = 4
  • THERMOCOUPLE_TYPE_R = 5
  • THERMOCOUPLE_TYPE_S = 6
  • THERMOCOUPLE_TYPE_T = 7
  • THERMOCOUPLE_TYPE_G8 = 8
  • THERMOCOUPLE_TYPE_G32 = 9
  • THERMOCOUPLE_FILTER_OPTION_50HZ = 0
  • THERMOCOUPLE_FILTER_OPTION_60HZ = 1
int thermocouple_get_configuration(Thermocouple *thermocouple, uint8_t *ret_averaging, uint8_t *ret_thermocouple_type, uint8_t *ret_filter)

Returns the configuration as set by thermocouple_set_configuration().

The following defines are available for this function:

  • THERMOCOUPLE_AVERAGING_1 = 1
  • THERMOCOUPLE_AVERAGING_2 = 2
  • THERMOCOUPLE_AVERAGING_4 = 4
  • THERMOCOUPLE_AVERAGING_8 = 8
  • THERMOCOUPLE_AVERAGING_16 = 16
  • THERMOCOUPLE_TYPE_B = 0
  • THERMOCOUPLE_TYPE_E = 1
  • THERMOCOUPLE_TYPE_J = 2
  • THERMOCOUPLE_TYPE_K = 3
  • THERMOCOUPLE_TYPE_N = 4
  • THERMOCOUPLE_TYPE_R = 5
  • THERMOCOUPLE_TYPE_S = 6
  • THERMOCOUPLE_TYPE_T = 7
  • THERMOCOUPLE_TYPE_G8 = 8
  • THERMOCOUPLE_TYPE_G32 = 9
  • THERMOCOUPLE_FILTER_OPTION_50HZ = 0
  • THERMOCOUPLE_FILTER_OPTION_60HZ = 1
int thermocouple_get_error_state(Thermocouple *thermocouple, bool *ret_over_under, bool *ret_open_circuit)

Returns the current error state. There are two possible errors:

  • Over/Under Voltage and
  • Open Circuit.

Over/Under Voltage happens for voltages below 0V or above 3.3V. In this case it is very likely that your thermocouple is defective. An Open Circuit error indicates that there is no thermocouple connected.

You can use the THERMOCOUPLE_CALLBACK_ERROR_STATE callback to automatically get triggered when the error state changes.

int thermocouple_get_api_version(Thermocouple *thermocouple, 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 thermocouple_get_response_expected(Thermocouple *thermocouple, 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 thermocouple_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 thermocouple_set_response_expected() for the list of function ID defines available for this function.

int thermocouple_set_response_expected(Thermocouple *thermocouple, 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:

  • THERMOCOUPLE_FUNCTION_SET_TEMPERATURE_CALLBACK_PERIOD = 2
  • THERMOCOUPLE_FUNCTION_SET_TEMPERATURE_CALLBACK_THRESHOLD = 4
  • THERMOCOUPLE_FUNCTION_SET_DEBOUNCE_PERIOD = 6
  • THERMOCOUPLE_FUNCTION_SET_CONFIGURATION = 10
int thermocouple_set_response_expected_all(Thermocouple *thermocouple, bool response_expected)

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

int thermocouple_get_identity(Thermocouple *thermocouple, 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 Bricklet.

Callback Configuration Functions

void thermocouple_register_callback(Thermocouple *thermocouple, 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 thermocouple_set_temperature_callback_period(Thermocouple *thermocouple, uint32_t period)

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

The THERMOCOUPLE_CALLBACK_TEMPERATURE callback is only triggered if the temperature has changed since the last triggering.

The default value is 0.

int thermocouple_get_temperature_callback_period(Thermocouple *thermocouple, uint32_t *ret_period)

Returns the period as set by thermocouple_set_temperature_callback_period().

int thermocouple_set_temperature_callback_threshold(Thermocouple *thermocouple, char option, int32_t min, int32_t max)

Sets the thresholds for the THERMOCOUPLE_CALLBACK_TEMPERATURE_REACHED callback.

The following options are possible:

Option Description
'x' Callback is turned off
'o' Callback is triggered when the temperature is outside the min and max values
'i' Callback is triggered when the temperature is inside the min and max values
'<' Callback is triggered when the temperature is smaller than the min value (max is ignored)
'>' Callback is triggered when the temperature is greater than the min value (max is ignored)

The default value is ('x', 0, 0).

The following defines are available for this function:

  • THERMOCOUPLE_THRESHOLD_OPTION_OFF = 'x'
  • THERMOCOUPLE_THRESHOLD_OPTION_OUTSIDE = 'o'
  • THERMOCOUPLE_THRESHOLD_OPTION_INSIDE = 'i'
  • THERMOCOUPLE_THRESHOLD_OPTION_SMALLER = '<'
  • THERMOCOUPLE_THRESHOLD_OPTION_GREATER = '>'
int thermocouple_get_temperature_callback_threshold(Thermocouple *thermocouple, char *ret_option, int32_t *ret_min, int32_t *ret_max)

Returns the threshold as set by thermocouple_set_temperature_callback_threshold().

The following defines are available for this function:

  • THERMOCOUPLE_THRESHOLD_OPTION_OFF = 'x'
  • THERMOCOUPLE_THRESHOLD_OPTION_OUTSIDE = 'o'
  • THERMOCOUPLE_THRESHOLD_OPTION_INSIDE = 'i'
  • THERMOCOUPLE_THRESHOLD_OPTION_SMALLER = '<'
  • THERMOCOUPLE_THRESHOLD_OPTION_GREATER = '>'
int thermocouple_set_debounce_period(Thermocouple *thermocouple, uint32_t debounce)

Sets the period in ms with which the threshold callback

is triggered, if the threshold

keeps being reached.

The default value is 100.

int thermocouple_get_debounce_period(Thermocouple *thermocouple, uint32_t *ret_debounce)

Returns the debounce period as set by thermocouple_set_debounce_period().

Callbacks

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

thermocouple_register_callback(&thermocouple, THERMOCOUPLE_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.

THERMOCOUPLE_CALLBACK_TEMPERATURE
void callback(int32_t temperature, void *user_data)

This callback is triggered periodically with the period that is set by thermocouple_set_temperature_callback_period(). The parameter is the temperature of the thermocouple.

The THERMOCOUPLE_CALLBACK_TEMPERATURE callback is only triggered if the temperature has changed since the last triggering.

THERMOCOUPLE_CALLBACK_TEMPERATURE_REACHED
void callback(int32_t temperature, void *user_data)

This callback is triggered when the threshold as set by thermocouple_set_temperature_callback_threshold() is reached. The parameter is the temperature of the thermocouple.

If the threshold keeps being reached, the callback is triggered periodically with the period as set by thermocouple_set_debounce_period().

THERMOCOUPLE_CALLBACK_ERROR_STATE
void callback(bool over_under, bool open_circuit, void *user_data)

This Callback is triggered every time the error state changes (see thermocouple_get_error_state()).

Constants

THERMOCOUPLE_DEVICE_IDENTIFIER

This constant is used to identify a Thermocouple Bricklet.

The thermocouple_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.

THERMOCOUPLE_DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Thermocouple Bricklet.