Python - RS232 Bricklet¶

Loopback¶

Download (example_loopback.py)

 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
41
42
43
44
45
46

#!/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()

Basic Functions¶

BrickletRS232(uid, ipcon)¶

Parameters:	uid -- string ipcon -- IPConnection

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 -- [chr, chr, ..57x.., chr] length -- int
Return type:	int

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 type:	([chr, chr, ..57x.., chr], int)

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.

The returned namedtuple has the variables message and length.

BrickletRS232.set_configuration(baudrate, parity, stopbits, wordlength, hardware_flowcontrol, software_flowcontrol)¶

Parameters:	baudrate -- int parity -- int stopbits -- int wordlength -- int hardware_flowcontrol -- int software_flowcontrol -- int
Return type:	None

Sets the configuration for the RS232 communication. Available options:

• Baudrate between 300 and 230400 baud.
• Parity of none, odd, even or forced parity.
• Stopbits can be 1 or 2.
• Word length of 5 to 8.
• Hard-/Software flow control can either be on or off but not both simultaneously on.

The default is: 115200 baud, parity none, 1 stop bit, word length 8, hard-/software flow control off.

The following constants are available for this function:

• 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
• BrickletRS232.PARITY_NONE = 0
• BrickletRS232.PARITY_ODD = 1
• BrickletRS232.PARITY_EVEN = 2
• BrickletRS232.PARITY_FORCED_PARITY_1 = 3
• BrickletRS232.PARITY_FORCED_PARITY_0 = 4
• BrickletRS232.STOPBITS_1 = 1
• BrickletRS232.STOPBITS_2 = 2
• BrickletRS232.WORDLENGTH_5 = 5
• BrickletRS232.WORDLENGTH_6 = 6
• BrickletRS232.WORDLENGTH_7 = 7
• BrickletRS232.WORDLENGTH_8 = 8
• BrickletRS232.HARDWARE_FLOWCONTROL_OFF = 0
• BrickletRS232.HARDWARE_FLOWCONTROL_ON = 1
• BrickletRS232.SOFTWARE_FLOWCONTROL_OFF = 0
• BrickletRS232.SOFTWARE_FLOWCONTROL_ON = 1

BrickletRS232.get_configuration()¶

Return type:	(int, int, int, int, int, int)

Returns the configuration as set by set_configuration().

The following constants are available for this function:

• 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
• BrickletRS232.PARITY_NONE = 0
• BrickletRS232.PARITY_ODD = 1
• BrickletRS232.PARITY_EVEN = 2
• BrickletRS232.PARITY_FORCED_PARITY_1 = 3
• BrickletRS232.PARITY_FORCED_PARITY_0 = 4
• BrickletRS232.STOPBITS_1 = 1
• BrickletRS232.STOPBITS_2 = 2
• BrickletRS232.WORDLENGTH_5 = 5
• BrickletRS232.WORDLENGTH_6 = 6
• BrickletRS232.WORDLENGTH_7 = 7
• BrickletRS232.WORDLENGTH_8 = 8
• BrickletRS232.HARDWARE_FLOWCONTROL_OFF = 0
• BrickletRS232.HARDWARE_FLOWCONTROL_ON = 1
• BrickletRS232.SOFTWARE_FLOWCONTROL_OFF = 0
• BrickletRS232.SOFTWARE_FLOWCONTROL_ON = 1

The returned namedtuple has the variables baudrate, parity, stopbits, wordlength, hardware_flowcontrol and software_flowcontrol.

BrickletRS232.set_break_condition(break_time)¶

Parameters:	break_time -- int
Return type:	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 (in ms).

New in version 2.0.2 (Plugin).

Advanced Functions¶

BrickletRS232.get_api_version()¶

Return type:	[int, int, int]

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.

BrickletRS232.get_response_expected(function_id)¶

Parameters:	function_id -- int
Return 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.

See set_response_expected() for the list of function ID constants available for this function.

BrickletRS232.set_response_expected(function_id, response_expected)¶

Parameters:	function_id -- int response_expected -- bool
Return type:	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 function ID constants are available for this function:

• 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 -- bool
Return type:	None

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

BrickletRS232.get_identity()¶

Return type:	(str, str, chr, [int, int, int], [int, int, int], int)

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.

The returned namedtuple has the variables uid, connected_uid, position, hardware_version, firmware_version and device_identifier.

Callback Configuration Functions¶

BrickletRS232.register_callback(callback_id, function)¶

Parameters:	callback_id -- int function -- callable
Return type:	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()¶

Return type:	None

Enables the CALLBACK_READ callback.

By default the callback is disabled.

BrickletRS232.disable_read_callback()¶

Return type:	None

Disables the CALLBACK_READ callback.

By default the callback is disabled.

BrickletRS232.is_read_callback_enabled()¶

Return type:	bool

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.

BrickletRS232.CALLBACK_READ¶

Parameters:	message -- [chr, chr, ..57x.., chr] length -- int

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¶

Parameters:	error -- int

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

The following constants are available for this function:

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

New in version 2.0.1 (Plugin).

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.