Software / API Bindings / Python / API Reference and Examples / Bricklets (Discontinued) / Dual Relay Bricklet

Python - Dual Relay Bricklet¶

This is the description of the Python 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 Python API bindings is part of their general description.

Examples¶

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

Simple¶

Download (example_simple.py)

#!/usr/bin/env python
# -*- coding: utf-8 -*-

HOST = "localhost"
PORT = 4223
UID = "XYZ" # Change XYZ to the UID of your Dual Relay Bricklet

import time

from tinkerforge.ip_connection import IPConnection
from tinkerforge.bricklet_dual_relay import BrickletDualRelay

if __name__ == "__main__":
    ipcon = IPConnection() # Create IP connection
    dr = BrickletDualRelay(UID, ipcon) # Create device object

    ipcon.connect(HOST, PORT) # Connect to brickd
    # Don't use device before ipcon is connected

    # Turn relays alternating on/off 10 times with 1 second delay
    for i in range(5):
        time.sleep(1)
        dr.set_state(True, False)
        time.sleep(1)
        dr.set_state(False, True)

    input("Press key to exit\n") # Use raw_input() in Python 2
    ipcon.disconnect()

API¶

Generally, every function of the Python bindings can throw an tinkerforge.ip_connection.Error exception that has a value and a description property. value can have different values:

Error.TIMEOUT = -1
Error.NOT_ADDED = -6 (unused since Python bindings version 2.0.0)
Error.ALREADY_CONNECTED = -7
Error.NOT_CONNECTED = -8
Error.INVALID_PARAMETER = -9
Error.NOT_SUPPORTED = -10
Error.UNKNOWN_ERROR_CODE = -11
Error.STREAM_OUT_OF_SYNC = -12
Error.INVALID_UID = -13
Error.NON_ASCII_CHAR_IN_SECRET = -14
Error.WRONG_DEVICE_TYPE = -15
Error.DEVICE_REPLACED = -16
Error.WRONG_RESPONSE_LENGTH = -17

All functions listed below are thread-safe.

Basic Functions¶

BrickletDualRelay(uid, ipcon)¶

Parameters:	uid – Type: str ipcon – Type: IPConnection
Returns:	dual_relay – Type: BrickletDualRelay

Creates an object with the unique device ID uid:

dual_relay = BrickletDualRelay("YOUR_DEVICE_UID", ipcon)

This object can then be used after the IP Connection is connected.

BrickletDualRelay.set_state(relay1, relay2)¶

Parameters:	relay1 – Type: bool, Default: False relay2 – Type: bool, Default: False
Returns:	None

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 get_state() or you can use set_selected_state().

All running monoflop timers will be aborted if this function is called.

BrickletDualRelay.get_state()¶

Return Object:	relay1 – Type: bool, Default: False relay2 – Type: bool, Default: False

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

Advanced Functions¶

BrickletDualRelay.set_monoflop(relay, state, time)¶

Parameters:	relay – Type: int, Range: [1 to 2] state – Type: bool time – Type: int, Unit: 1 ms, Range: [0 to 2³² - 1]
Returns:	None

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 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.

BrickletDualRelay.get_monoflop(relay)¶

Parameters:	relay – Type: int, Range: [1 to 2]
Return Object:	state – Type: bool time – Type: int, Unit: 1 ms, Range: [0 to 2³² - 1] time_remaining – Type: int, Unit: 1 ms, Range: [0 to 2³² - 1]

Returns (for the given relay) the current state and the time as set by 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.

BrickletDualRelay.set_selected_state(relay, state)¶

Parameters:	relay – Type: int, Range: [1 to 2] state – Type: bool
Returns:	None

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

A running monoflop timer for the selected relay will be aborted if this function is called.

The other relay remains untouched.

BrickletDualRelay.get_identity()¶

Return Object:

Return Object:	uid – Type: str, Length: up to 8 connected_uid – Type: str, Length: up to 8 position – Type: chr, Range: ["a" to "h", "z"] hardware_version – Type: [int, ...], Length: 3 0: major – Type: int, Range: [0 to 255] 1: minor – Type: int, Range: [0 to 255] 2: revision – Type: int, Range: [0 to 255] firmware_version – Type: [int, ...], Length: 3 0: major – Type: int, Range: [0 to 255] 1: minor – Type: int, Range: [0 to 255] 2: revision – Type: int, Range: [0 to 255] device_identifier – Type: int, Range: [0 to 2¹⁶ - 1]

uid – Type: str, Length: up to 8
connected_uid – Type: str, Length: up to 8
position – Type: chr, Range: ["a" to "h", "z"]
hardware_version – Type: [int, ...], Length: 3

0: major – Type: int, Range: [0 to 255]
1: minor – Type: int, Range: [0 to 255]
2: revision – Type: int, Range: [0 to 255]

firmware_version – Type: [int, ...], Length: 3

0: major – Type: int, Range: [0 to 255]
1: minor – Type: int, Range: [0 to 255]
2: revision – Type: int, Range: [0 to 255]

device_identifier – Type: int, Range: [0 to 2¹⁶ - 1]

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', 'd', 'e', 'f', 'g' or 'h' (Bricklet Port). A Bricklet connected to an Isolator Bricklet is always at position 'z'.

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

Callback Configuration Functions¶

BrickletDualRelay.register_callback(callback_id, function)¶

Parameters:	callback_id – Type: int function – Type: callable
Returns:	None

Registers the given function with the given callback_id.

The available callback 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 register_callback() function of the device object. The first parameter is the callback ID and the second parameter the callback function:

def my_callback(param):
    print(param)

dual_relay.register_callback(BrickletDualRelay.CALLBACK_EXAMPLE, my_callback)

The available constants with inherent number and type of parameters 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.

BrickletDualRelay.CALLBACK_MONOFLOP_DONE¶

Callback Parameters:	relay – Type: int, Range: [1 to 2] state – Type: bool

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).

Virtual Functions¶

Virtual functions don't communicate with the device itself, but operate only on the API bindings device object. They can be called without the corresponding IP Connection object being connected.

BrickletDualRelay.get_api_version()¶

Return Object:	api_version – Type: [int, ...], Length: 3 0: major – Type: int, Range: [0 to 255] 1: minor – Type: int, Range: [0 to 255] 2: revision – Type: int, Range: [0 to 255]

Returns the version of the API definition 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.

BrickletDualRelay.get_response_expected(function_id)¶

Parameters:	function_id – Type: int, Range: See constants
Returns:	response_expected – Type: bool

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 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:

BrickletDualRelay.FUNCTION_SET_STATE = 1
BrickletDualRelay.FUNCTION_SET_MONOFLOP = 3
BrickletDualRelay.FUNCTION_SET_SELECTED_STATE = 6

BrickletDualRelay.set_response_expected(function_id, response_expected)¶

Parameters:	function_id – Type: int, Range: See constants response_expected – Type: bool
Returns:	None

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:

BrickletDualRelay.FUNCTION_SET_STATE = 1
BrickletDualRelay.FUNCTION_SET_MONOFLOP = 3
BrickletDualRelay.FUNCTION_SET_SELECTED_STATE = 6

BrickletDualRelay.set_response_expected_all(response_expected)¶

Parameters:	response_expected – Type: bool
Returns:	None

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

Constants¶

BrickletDualRelay.DEVICE_IDENTIFIER¶

This constant is used to identify a Dual Relay Bricklet.

The get_identity() function and the IPConnection.CALLBACK_ENUMERATE callback of the IP Connection have a device_identifier parameter to specify the Brick's or Bricklet's type.

BrickletDualRelay.DEVICE_DISPLAY_NAME¶: This constant represents the human readable name of a Dual Relay Bricklet.