C/C++ - Dual Relay Bricklet – Tinkerforge

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# C/C++ - Dual Relay Bricklet

This is the description of the C/C++ API bindings for the Dual Relay Bricklet. General information and technical specifications for the Dual Relay 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_dual_relay.h"

    #define HOST "localhost"
    #define PORT 4223
    #define UID "xyz" // Change to your UID

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

        // Create device object
        DualRelay dr;
        dual_relay_create(&dr, UID, &ipcon);

        // Connect to brickd
        if(ipcon_connect(&ipcon, HOST, PORT) < 0) {
            fprintf(stderr, "Could not connect\n");
            exit(1);
        }
        // Don't use device before ipcon is connected

        // Turn relay 1 on and relay 2 off.
        dual_relay_set_state(&dr, true, false);

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

## 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

as defined in `ip_connection.h`.

All functions listed below are thread-safe.

### Basic Functions

void `dual_relay_create`(DualRelay *dual_relay, const char *uid, IPConnection *ipcon)

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

      DualRelay dual_relay;
      dual_relay_create(&dual_relay, "YOUR_DEVICE_UID", &ipcon);

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

void `dual_relay_destroy`(DualRelay *dual_relay)

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

int `dual_relay_set_state`(DualRelay *dual_relay, bool relay1, bool relay2)

  Sets the state of the relays, true means on and false means off. For example: (true, false) turns relay 1 on and relay 2 off.

  If you just want to set one of the relays and don't know the current state of the other relay, you can get the state with `dual_relay_get_state()` or you can use `dual_relay_set_selected_state()`.

  Running monoflop timers will be overwritten if this function is called.

  The default value is (false, false).

int `dual_relay_get_state`(DualRelay *dual_relay, bool *ret_relay1, bool *ret_relay2)

  Returns the state of the relays, true means on and false means off.

### Advanced Functions

int `dual_relay_set_monoflop`(DualRelay *dual_relay, uint8_t relay, bool state, uint32_t time)

  The first parameter can be 1 or 2 (relay 1 or relay 2). The second parameter is the desired state of the relay (true means on and false means off). The third parameter indicates the time (in ms) that the relay should hold the state.

  If this function is called with the parameters (1, true, 1500): Relay 1 will turn on and in 1.5s it will turn off again.

  A monoflop can be used as a failsafe mechanism. For example: Lets assume you have a RS485 bus and a Dual Relay Bricklet connected to one of the slave stacks. You can now call this function every second, with a time parameter of two seconds. The relay will be on all the time. If now the RS485 connection is lost, the relay will turn off in at most two seconds.

int `dual_relay_get_monoflop`(DualRelay *dual_relay, uint8_t relay, bool *ret_state, uint32_t *ret_time, uint32_t *ret_time_remaining)

  Returns (for the given relay) the current state and the time as set by `dual_relay_set_monoflop()` as well as the remaining time until the state flips.

  If the timer is not running currently, the remaining time will be returned as 0.

int `dual_relay_set_selected_state`(DualRelay *dual_relay, uint8_t relay, bool state)

  Sets the state of the selected relay (1 or 2), true means on and false means off.

  The other relay remains untouched.

int `dual_relay_get_api_version`(DualRelay *dual_relay, 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 `dual_relay_get_response_expected`(DualRelay *dual_relay, 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 `dual_relay_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 `dual_relay_set_response_expected()` for the list of function ID defines available for this function.

int `dual_relay_set_response_expected`(DualRelay *dual_relay, 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 and callbacks it is always disabled.

  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:

  - DUAL_RELAY_FUNCTION_SET_STATE = 1
  - DUAL_RELAY_FUNCTION_SET_MONOFLOP = 3
  - DUAL_RELAY_FUNCTION_SET_SELECTED_STATE = 6

int `dual_relay_set_response_expected_all`(DualRelay *dual_relay, bool response_expected)

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

int `dual_relay_get_identity`(DualRelay *dual_relay, 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 `dual_relay_register_callback`(DualRelay *dual_relay, uint8_t id, void *callback, void *user_data)

  Registers a callback with ID `id` to the function `callback`. The `user_data` will be given as a parameter of the callback.

  The available IDs with corresponding function signatures are listed below.

### Callbacks

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

>     dual_relay_register_callback(&dual_relay, DUAL_RELAY_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.

`DUAL_RELAY_CALLBACK_MONOFLOP_DONE`

      void callback(uint8_t relay, bool state, void *user_data)

  This callback is triggered whenever a monoflop timer reaches 0. The parameter contain the relay (1 or 2) and the current state of the relay (the state after the monoflop).

### Constants

`DUAL_RELAY_DEVICE_IDENTIFIER`

  This constant is used to identify a Dual Relay Bricklet.

  The `dual_relay_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.

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