Python - RS232 Bricklet

This is the description of the Python API bindings for the RS232 Bricklet. General information and technical specifications for the RS232 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).

Loopback

Download (example_loopback.py)

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

# For this example connect the RX1 and TX pin to receive the send message

HOST = "localhost"
PORT = 4223
UID = "XYZ" # Change XYZ to the UID of your RS232 Bricklet

from tinkerforge.ip_connection import IPConnection
from tinkerforge.bricklet_rs232 import BrickletRS232

# Convert string to char array with length 60, as needed by write
def string_to_char_list(message):
    chars = list(message)
    chars.extend(['\0']*(60 - len(message)))
    return chars, len(message)

# Assume that the message consists of ASCII characters and
# convert it from an array of chars to a string
def char_list_to_string(message, length):
    return ''.join(message[:length])

# Callback function for read callback
def cb_read(message, length):
    s = char_list_to_string(message, length)
    print('Message (Length: ' + str(length) + '): "' + s + '"')

if __name__ == "__main__":
    ipcon = IPConnection() # Create IP connection
    rs232 = BrickletRS232(UID, ipcon) # Create device object

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

    # Register read callback to function cb_read
    rs232.register_callback(rs232.CALLBACK_READ, cb_read)

    # Enable read callback
    rs232.enable_read_callback()

    # Write "test" string
    rs232.write(*string_to_char_list('test'))

    raw_input("Press key to exit\n") # Use input() in Python 3
    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

All functions listed below are thread-safe.

Basic Functions

BrickletRS232(uid, ipcon)
Parameters:
  • uid – Type: str
  • ipcon – Type: IPConnection
Returns:
  • rs232 – Type: BrickletRS232

Creates an object with the unique device ID uid:

rs232 = BrickletRS232("YOUR_DEVICE_UID", ipcon)

This object can then be used after the IP Connection is connected (see examples above).

BrickletRS232.write(message, length)
Parameters:
  • message – Type: [chr, ...], Length: 60
  • length – Type: int, Range: [0 to 60]
Returns:
  • written – Type: int, Range: [0 to 60]

Writes a string of up to 60 characters to the RS232 interface. The string can be binary data, ASCII or similar is not necessary.

The length of the string has to be given as an additional parameter.

The return value is the number of bytes that could be written.

See set_configuration() for configuration possibilities regarding baudrate, parity and so on.

BrickletRS232.read()
Return Object:
  • message – Type: [chr, ...], Length: 60
  • length – Type: int, Range: [0 to 60]

Returns the currently buffered message. The maximum length of message is 60. If the length is given as 0, there was no new data available.

Instead of polling with this function, you can also use callbacks. See enable_read_callback() and CALLBACK_READ callback.

BrickletRS232.set_configuration(baudrate, parity, stopbits, wordlength, hardware_flowcontrol, software_flowcontrol)
Parameters:
  • baudrate – Type: int, Range: See constants, Default: 11
  • parity – Type: int, Range: See constants, Default: 0
  • stopbits – Type: int, Range: See constants, Default: 1
  • wordlength – Type: int, Range: See constants, Default: 8
  • hardware_flowcontrol – Type: int, Range: See constants, Default: 0
  • software_flowcontrol – Type: int, Range: See constants, Default: 0
Returns:
  • None

Sets the configuration for the RS232 communication.

Hard-/Software flow control can either be on or off but not both simultaneously on.

The following constants are available for this function:

For baudrate:

  • BrickletRS232.BAUDRATE_300 = 0
  • BrickletRS232.BAUDRATE_600 = 1
  • BrickletRS232.BAUDRATE_1200 = 2
  • BrickletRS232.BAUDRATE_2400 = 3
  • BrickletRS232.BAUDRATE_4800 = 4
  • BrickletRS232.BAUDRATE_9600 = 5
  • BrickletRS232.BAUDRATE_14400 = 6
  • BrickletRS232.BAUDRATE_19200 = 7
  • BrickletRS232.BAUDRATE_28800 = 8
  • BrickletRS232.BAUDRATE_38400 = 9
  • BrickletRS232.BAUDRATE_57600 = 10
  • BrickletRS232.BAUDRATE_115200 = 11
  • BrickletRS232.BAUDRATE_230400 = 12

For parity:

  • BrickletRS232.PARITY_NONE = 0
  • BrickletRS232.PARITY_ODD = 1
  • BrickletRS232.PARITY_EVEN = 2
  • BrickletRS232.PARITY_FORCED_PARITY_1 = 3
  • BrickletRS232.PARITY_FORCED_PARITY_0 = 4

For stopbits:

  • BrickletRS232.STOPBITS_1 = 1
  • BrickletRS232.STOPBITS_2 = 2

For wordlength:

  • BrickletRS232.WORDLENGTH_5 = 5
  • BrickletRS232.WORDLENGTH_6 = 6
  • BrickletRS232.WORDLENGTH_7 = 7
  • BrickletRS232.WORDLENGTH_8 = 8

For hardware_flowcontrol:

  • BrickletRS232.HARDWARE_FLOWCONTROL_OFF = 0
  • BrickletRS232.HARDWARE_FLOWCONTROL_ON = 1

For software_flowcontrol:

  • BrickletRS232.SOFTWARE_FLOWCONTROL_OFF = 0
  • BrickletRS232.SOFTWARE_FLOWCONTROL_ON = 1
BrickletRS232.get_configuration()
Return Object:
  • baudrate – Type: int, Range: See constants, Default: 11
  • parity – Type: int, Range: See constants, Default: 0
  • stopbits – Type: int, Range: See constants, Default: 1
  • wordlength – Type: int, Range: See constants, Default: 8
  • hardware_flowcontrol – Type: int, Range: See constants, Default: 0
  • software_flowcontrol – Type: int, Range: See constants, Default: 0

Returns the configuration as set by set_configuration().

The following constants are available for this function:

For baudrate:

  • BrickletRS232.BAUDRATE_300 = 0
  • BrickletRS232.BAUDRATE_600 = 1
  • BrickletRS232.BAUDRATE_1200 = 2
  • BrickletRS232.BAUDRATE_2400 = 3
  • BrickletRS232.BAUDRATE_4800 = 4
  • BrickletRS232.BAUDRATE_9600 = 5
  • BrickletRS232.BAUDRATE_14400 = 6
  • BrickletRS232.BAUDRATE_19200 = 7
  • BrickletRS232.BAUDRATE_28800 = 8
  • BrickletRS232.BAUDRATE_38400 = 9
  • BrickletRS232.BAUDRATE_57600 = 10
  • BrickletRS232.BAUDRATE_115200 = 11
  • BrickletRS232.BAUDRATE_230400 = 12

For parity:

  • BrickletRS232.PARITY_NONE = 0
  • BrickletRS232.PARITY_ODD = 1
  • BrickletRS232.PARITY_EVEN = 2
  • BrickletRS232.PARITY_FORCED_PARITY_1 = 3
  • BrickletRS232.PARITY_FORCED_PARITY_0 = 4

For stopbits:

  • BrickletRS232.STOPBITS_1 = 1
  • BrickletRS232.STOPBITS_2 = 2

For wordlength:

  • BrickletRS232.WORDLENGTH_5 = 5
  • BrickletRS232.WORDLENGTH_6 = 6
  • BrickletRS232.WORDLENGTH_7 = 7
  • BrickletRS232.WORDLENGTH_8 = 8

For hardware_flowcontrol:

  • BrickletRS232.HARDWARE_FLOWCONTROL_OFF = 0
  • BrickletRS232.HARDWARE_FLOWCONTROL_ON = 1

For software_flowcontrol:

  • BrickletRS232.SOFTWARE_FLOWCONTROL_OFF = 0
  • BrickletRS232.SOFTWARE_FLOWCONTROL_ON = 1
BrickletRS232.set_break_condition(break_time)
Parameters:
  • break_time – Type: int, Unit: 1 ms, Range: [0 to 216 - 1]
Returns:
  • None

Sets a break condition (the TX output is forced to a logic 0 state). The parameter sets the hold-time of the break condition.

New in version 2.0.2 (Plugin).

Advanced Functions

BrickletRS232.get_identity()
Return Object:
  • uid – Type: str, Length: up to 8
  • connected_uid – Type: str, Length: up to 8
  • position – Type: chr, Range: ["a" to "h", "i", "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). The Raspberry Pi HAT (Zero) Brick is always at position 'i' and the Bricklet connected to an Isolator Bricklet is always as 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

BrickletRS232.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.

BrickletRS232.enable_read_callback()
Returns:
  • None

Enables the CALLBACK_READ callback.

By default the callback is disabled.

BrickletRS232.disable_read_callback()
Returns:
  • None

Disables the CALLBACK_READ callback.

By default the callback is disabled.

BrickletRS232.is_read_callback_enabled()
Returns:
  • enabled – Type: bool, Default: False

Returns true if the CALLBACK_READ callback is enabled, false otherwise.

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)

rs232.register_callback(BrickletRS232.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.

BrickletRS232.CALLBACK_READ
Callback Parameters:
  • message – Type: [chr, ...], Length: 60
  • length – Type: int, Range: [1 to 60]

This callback is called if new data is available. The message has a maximum size of 60 characters. The actual length of the message is given in addition.

To enable this callback, use enable_read_callback().

BrickletRS232.CALLBACK_ERROR
Callback Parameters:
  • error – Type: int, Range: See constants

This callback is called if an error occurs. Possible errors are overrun, parity or framing error.

The following constants are available for this function:

For error:

  • BrickletRS232.ERROR_OVERRUN = 1
  • BrickletRS232.ERROR_PARITY = 2
  • BrickletRS232.ERROR_FRAMING = 4

New in version 2.0.1 (Plugin).

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.

BrickletRS232.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.

BrickletRS232.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 send and errors are silently ignored, because they cannot be detected.

The following constants are available for this function:

For function_id:

  • BrickletRS232.FUNCTION_ENABLE_READ_CALLBACK = 3
  • BrickletRS232.FUNCTION_DISABLE_READ_CALLBACK = 4
  • BrickletRS232.FUNCTION_SET_CONFIGURATION = 6
  • BrickletRS232.FUNCTION_SET_BREAK_CONDITION = 10
BrickletRS232.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.

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:

For function_id:

  • BrickletRS232.FUNCTION_ENABLE_READ_CALLBACK = 3
  • BrickletRS232.FUNCTION_DISABLE_READ_CALLBACK = 4
  • BrickletRS232.FUNCTION_SET_CONFIGURATION = 6
  • BrickletRS232.FUNCTION_SET_BREAK_CONDITION = 10
BrickletRS232.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

BrickletRS232.DEVICE_IDENTIFIER

This constant is used to identify a RS232 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.

BrickletRS232.DEVICE_DISPLAY_NAME

This constant represents the human readable name of a RS232 Bricklet.