pySerial API¶
Classes¶
Native ports¶
- class serial.Serial¶
- __init__(port=None, baudrate=9600, bytesize=EIGHTBITS, parity=PARITY_NONE, stopbits=STOPBITS_ONE, timeout=None, xonxoff=False, rtscts=False, write_timeout=None, dsrdtr=False, inter_byte_timeout=None, exclusive=None)¶
- Parameters:
port – Device name or
None
.baudrate (int) – Baud rate such as 9600 or 115200 etc.
bytesize – Number of data bits. Possible values:
FIVEBITS
,SIXBITS
,SEVENBITS
,EIGHTBITS
parity – Enable parity checking. Possible values:
PARITY_NONE
,PARITY_EVEN
,PARITY_ODD
PARITY_MARK
,PARITY_SPACE
stopbits – Number of stop bits. Possible values:
STOPBITS_ONE
,STOPBITS_ONE_POINT_FIVE
,STOPBITS_TWO
timeout (float) – Set a read timeout value in seconds.
xonxoff (bool) – Enable software flow control.
rtscts (bool) – Enable hardware (RTS/CTS) flow control.
dsrdtr (bool) – Enable hardware (DSR/DTR) flow control.
write_timeout (float) – Set a write timeout value in seconds.
inter_byte_timeout (float) – Inter-character timeout,
None
to disable (default).exclusive (bool) – Set exclusive access mode (POSIX only). A port cannot be opened in exclusive access mode if it is already open in exclusive access mode.
- Raises:
ValueError – Will be raised when parameter are out of range, e.g. baud rate, data bits.
SerialException – In case the device can not be found or can not be configured.
The port is immediately opened on object creation, when a port is given. It is not opened when port is
None
and a successive call toopen()
is required.port is a device name: depending on operating system. e.g.
/dev/ttyUSB0
on GNU/Linux orCOM3
on Windows.The parameter baudrate can be one of the standard values: 50, 75, 110, 134, 150, 200, 300, 600, 1200, 1800, 2400, 4800, 9600, 19200, 38400, 57600, 115200. These are well supported on all platforms.
Standard values above 115200, such as: 230400, 460800, 500000, 576000, 921600, 1000000, 1152000, 1500000, 2000000, 2500000, 3000000, 3500000, 4000000 also work on many platforms and devices.
Non-standard values are also supported on some platforms (GNU/Linux, MAC OSX >= Tiger, Windows). Though, even on these platforms some serial ports may reject non-standard values.
Possible values for the parameter timeout which controls the behavior of
read()
:timeout = None
: wait forever / until requested number of bytes are receivedtimeout = 0
: non-blocking mode, return immediately in any case, returning zero or more, up to the requested number of bytestimeout = x
: set timeout tox
seconds (float allowed) returns immediately when the requested number of bytes are available, otherwise wait until the timeout expires and return all bytes that were received until then.
write()
is blocking by default, unless write_timeout is set. For possible values refer to the list for timeout above.Note that enabling both flow control methods (xonxoff and rtscts) together may not be supported. It is common to use one of the methods at once, not both.
dsrdtr is not supported by all platforms (silently ignored). Setting it to
None
has the effect that its state follows rtscts.Also consider using the function
serial_for_url()
instead of creating Serial instances directly.Changed in version 2.5: dsrdtr now defaults to
False
(instead of None)Changed in version 3.0: numbers as port argument are no longer supported
Added in version 3.3:
exclusive
flag
- close()¶
Close port immediately.
- __del__()¶
Destructor, close port when serial port instance is freed.
The following methods may raise
SerialException
when applied to a closed port.- read(size=1)¶
- Parameters:
size – Number of bytes to read.
- Returns:
Bytes read from the port.
- Return type:
bytes
Read size bytes from the serial port. If a timeout is set it may return less characters as requested. With no timeout it will block until the requested number of bytes is read.
Changed in version 2.5: Returns an instance of
bytes
when available (Python 2.6 and newer) andstr
otherwise.
- read_until(expected=LF, size=None)¶
- Parameters:
expected – The byte string to search for.
size – Number of bytes to read.
- Returns:
Bytes read from the port.
- Return type:
bytes
Read until an expected sequence is found (’\n’ by default), the size is exceeded or until timeout occurs. If a timeout is set it may return less characters as requested. With no timeout it will block until the requested number of bytes is read.
Changed in version 2.5: Returns an instance of
bytes
when available (Python 2.6 and newer) andstr
otherwise.
- write(data)¶
- Parameters:
data – Data to send.
- Returns:
Number of bytes written.
- Return type:
int
- Raises:
SerialTimeoutException – In case a write timeout is configured for the port and the time is exceeded.
Write the bytes data to the port. This should be of type
bytes
(or compatible such asbytearray
ormemoryview
). Unicode strings must be encoded (e.g.'hello'.encode('utf-8')
.
Changed in version 2.5: Accepts instances of
bytes
andbytearray
when available (Python 2.6 and newer) andstr
otherwise.Changed in version 2.5: Write returned
None
in previous versions.- flush()¶
Flush of file like objects. In this case, wait until all data is written.
- in_waiting¶
- Getter:
Get the number of bytes in the input buffer
- Type:
int
Return the number of bytes in the receive buffer.
Changed in version 3.0: changed to property from
inWaiting()
- out_waiting¶
- Getter:
Get the number of bytes in the output buffer
- Type:
int
- Platform:
Posix
- Platform:
Windows
Return the number of bytes in the output buffer.
Changed in version 2.7: (Posix support added)
Changed in version 3.0: changed to property from
outWaiting()
- reset_input_buffer()¶
Flush input buffer, discarding all its contents.
Changed in version 3.0: renamed from
flushInput()
- reset_output_buffer()¶
Clear output buffer, aborting the current output and discarding all that is in the buffer.
Note, for some USB serial adapters, this may only flush the buffer of the OS and not all the data that may be present in the USB part.
Changed in version 3.0: renamed from
flushOutput()
- send_break(duration=0.25)¶
- Parameters:
duration (float) – Time in seconds, to activate the BREAK condition.
Send break condition. Timed, returns to idle state after given duration.
- break_condition¶
- Getter:
Get the current BREAK state
- Setter:
Control the BREAK state
- Type:
bool
When set to
True
activate BREAK condition, else disable. Controls TXD. When active, no transmitting is possible.
- rts¶
- Setter:
Set the state of the RTS line
- Getter:
Return the state of the RTS line
- Type:
bool
Set RTS line to specified logic level. It is possible to assign this value before opening the serial port, then the value is applied upon
open()
(with restrictions, seeopen()
).
- dtr¶
- Setter:
Set the state of the DTR line
- Getter:
Return the state of the DTR line
- Type:
bool
Set DTR line to specified logic level. It is possible to assign this value before opening the serial port, then the value is applied upon
open()
(with restrictions, seeopen()
).
Read-only attributes:
- name¶
- Getter:
Device name.
- Type:
str
Added in version 2.5.
- cts¶
- Getter:
Get the state of the CTS line
- Type:
bool
Return the state of the CTS line.
- dsr¶
- Getter:
Get the state of the DSR line
- Type:
bool
Return the state of the DSR line.
- ri¶
- Getter:
Get the state of the RI line
- Type:
bool
Return the state of the RI line.
- cd¶
- Getter:
Get the state of the CD line
- Type:
bool
Return the state of the CD line
- is_open¶
- Getter:
Get the state of the serial port, whether it’s open.
- Type:
bool
New values can be assigned to the following attributes (properties), the port will be reconfigured, even if it’s opened at that time:
- port¶
- Type:
str
Read or write port. When the port is already open, it will be closed and reopened with the new setting.
- baudrate¶
- Getter:
Get current baud rate
- Setter:
Set new baud rate
- Type:
int
Read or write current baud rate setting.
- bytesize¶
- Getter:
Get current byte size
- Setter:
Set new byte size. Possible values:
FIVEBITS
,SIXBITS
,SEVENBITS
,EIGHTBITS
- Type:
int
Read or write current data byte size setting.
- parity¶
- Getter:
Get current parity setting
- Setter:
Set new parity mode. Possible values:
PARITY_NONE
,PARITY_EVEN
,PARITY_ODD
PARITY_MARK
,PARITY_SPACE
Read or write current parity setting.
- stopbits¶
- Getter:
Get current stop bit setting
- Setter:
Set new stop bit setting. Possible values:
STOPBITS_ONE
,STOPBITS_ONE_POINT_FIVE
,STOPBITS_TWO
Read or write current stop bit width setting.
- timeout¶
- Getter:
Get current read timeout setting
- Setter:
Set read timeout
- Type:
float (seconds)
Read or write current read timeout setting.
- write_timeout¶
- Getter:
Get current write timeout setting
- Setter:
Set write timeout
- Type:
float (seconds)
Read or write current write timeout setting.
Changed in version 3.0: renamed from
writeTimeout
- inter_byte_timeout¶
- Getter:
Get current inter byte timeout setting
- Setter:
Disable (
None
) or enable the inter byte timeout- Type:
float or None
Read or write current inter byte timeout setting.
Changed in version 3.0: renamed from
interCharTimeout
- xonxoff¶
- Getter:
Get current software flow control setting
- Setter:
Enable or disable software flow control
- Type:
bool
Read or write current software flow control rate setting.
- rtscts¶
- Getter:
Get current hardware flow control setting
- Setter:
Enable or disable hardware flow control
- Type:
bool
Read or write current hardware flow control setting.
- dsrdtr¶
- Getter:
Get current hardware flow control setting
- Setter:
Enable or disable hardware flow control
- Type:
bool
Read or write current hardware flow control setting.
- rs485_mode¶
- Getter:
Get the current RS485 settings
- Setter:
Disable (
None
) or enable the RS485 settings- Type:
rs485.RS485Settings
orNone
- Platform:
Posix (Linux, limited set of hardware)
- Platform:
Windows (only RTS on TX possible)
Attribute to configure RS485 support. When set to an instance of
rs485.RS485Settings
and supported by OS, RTS will be active when data is sent and inactive otherwise (for reception). Thers485.RS485Settings
class provides additional settings supported on some platforms.Added in version 3.0.
The following constants are also provided:
- BAUDRATES¶
A list of valid baud rates. The list may be incomplete, such that higher and/or intermediate baud rates may also be supported by the device (Read Only).
- BYTESIZES¶
A list of valid byte sizes for the device (Read Only).
- PARITIES¶
A list of valid parities for the device (Read Only).
- STOPBITS¶
A list of valid stop bit widths for the device (Read Only).
The following methods are for compatibility with the
io
library.- readable()¶
- Returns:
True
Added in version 2.5.
- writable()¶
- Returns:
True
Added in version 2.5.
- seekable()¶
- Returns:
False
Added in version 2.5.
- readinto(b)¶
- Parameters:
b – bytearray or array instance
- Returns:
Number of byte read
Read up to len(b) bytes into
bytearray
b and return the number of bytes read.Added in version 2.5.
- readline(size=-1)¶
Provided via
io.IOBase.readline()
- readlines(hint=-1)¶
Provided via
io.IOBase.readlines()
- writelines(lines)¶
Provided via
io.IOBase.writelines()
The port settings can be read and written as dictionary. The following keys are supported:
write_timeout
,inter_byte_timeout
,dsrdtr
,baudrate
,timeout
,parity
,bytesize
,rtscts
,stopbits
,xonxoff
- get_settings()¶
- Returns:
a dictionary with current port settings.
- Return type:
dict
Get a dictionary with port settings. This is useful to backup the current settings so that a later point in time they can be restored using
apply_settings()
.Note that the state of control lines (RTS/DTR) are not part of the settings.
Added in version 2.5.
Changed in version 3.0: renamed from
getSettingsDict
- apply_settings(d)¶
- Parameters:
d (dict) – a dictionary with port settings.
Applies a dictionary that was created by
get_settings()
. Only changes are applied and when a key is missing, it means that the setting stays unchanged.Note that control lines (RTS/DTR) are not changed.
Added in version 2.5.
Changed in version 3.0: renamed from
applySettingsDict
This class can be used as context manager. The serial port is closed when the context is left.
- __enter__()¶
- Returns:
Serial instance
Returns the instance that was used in the
with
statement.Example:
>>> with serial.serial_for_url(port) as s: ... s.write(b'hello')
The port is opened automatically:
>>> port = serial.Serial() >>> port.port = '...' >>> with port as s: ... s.write(b'hello')
Which also means that
with
statements can be used repeatedly, each time opening and closing the port.Changed in version 3.4: the port is automatically opened
- __exit__(exc_type, exc_val, exc_tb)¶
Closes serial port (exceptions are not handled by
__exit__
).
Platform specific methods.
Warning
Programs using the following methods and attributes are not portable to other platforms!
- nonblocking()¶
- Platform:
Posix
Deprecated since version 3.2: The serial port is already opened in this mode. This method is not needed and going away.
- fileno()¶
- Platform:
Posix
- Returns:
File descriptor.
Return file descriptor number for the port that is opened by this object. It is useful when serial ports are used with
select
.
- set_input_flow_control(enable)¶
- Platform:
Posix
- Parameters:
enable (bool) – Set flow control state.
Manually control flow - when software flow control is enabled.
This will send XON (true) and XOFF (false) to the other device.
Added in version 2.7: (Posix support added)
Changed in version 3.0: renamed from
flowControlOut
- set_output_flow_control(enable)¶
- Platform:
Posix (HW and SW flow control)
- Platform:
Windows (SW flow control only)
- Parameters:
enable (bool) – Set flow control state.
Manually control flow of outgoing data - when hardware or software flow control is enabled.
Sending will be suspended when called with
False
and enabled when called withTrue
.Changed in version 2.7: (renamed on Posix, function was called
flowControl
)Changed in version 3.0: renamed from
setXON
- cancel_read()¶
- Platform:
Posix
- Platform:
Windows
Cancel a pending read operation from another thread. A blocking
read()
call is aborted immediately.read()
will not report any error but return all data received up to that point (similar to a timeout).On Posix a call to cancel_read() may cancel a future
read()
call.Added in version 3.1.
- cancel_write()¶
- Platform:
Posix
- Platform:
Windows
Cancel a pending write operation from another thread. The
write()
method will return immediately (no error indicated). However the OS may still be sending from the buffer, a separate call toreset_output_buffer()
may be needed.On Posix a call to cancel_write() may cancel a future
write()
call.Added in version 3.1.
Note
The following members are deprecated and will be removed in a future release.
- inWaiting()¶
Deprecated since version 3.0: see
in_waiting
- writeTimeout¶
Deprecated since version 3.0: see
write_timeout
- interCharTimeout¶
Deprecated since version 3.0: see
inter_byte_timeout
- sendBreak(duration=0.25)¶
Deprecated since version 3.0: see
send_break()
- flushInput()¶
Deprecated since version 3.0: see
reset_input_buffer()
- flushOutput()¶
Deprecated since version 3.0: see
reset_output_buffer()
- setBreak(level=True)¶
Deprecated since version 3.0: see
break_condition
- getSettingsDict()¶
Deprecated since version 3.0: see
get_settings()
- applySettingsDict(d)¶
Deprecated since version 3.0: see
apply_settings()
- outWaiting()¶
Deprecated since version 3.0: see
out_waiting
- setXON(level=True)¶
Deprecated since version 3.0: see
set_output_flow_control()
- flowControlOut(enable)¶
Deprecated since version 3.0: see
set_input_flow_control()
- rtsToggle¶
- Platform:
Windows
Attribute to configure RTS toggle control setting. When enabled and supported by OS, RTS will be active when data is available and inactive if no data is available.
Added in version 2.6.
Changed in version 3.0: (removed, see
rs485_mode
instead)
Implementation detail: some attributes and functions are provided by the
class serial.SerialBase
which inherits from io.RawIOBase
and some by the platform specific class and others by the base class
mentioned above.
RS485 support¶
The Serial
class has a Serial.rs485_mode
attribute which allows to
enable RS485 specific support on some platforms. Currently Windows and Linux
(only a small number of devices) are supported.
Serial.rs485_mode
needs to be set to an instance of
rs485.RS485Settings
to enable or to None
to disable this feature.
Usage:
import serial
import serial.rs485
ser = serial.Serial(...)
ser.rs485_mode = serial.rs485.RS485Settings(...)
ser.write(b'hello')
There is a subclass rs485.RS485
available to emulate the RS485 support
on regular serial ports (serial.rs485
needs to be imported).
- class rs485.RS485Settings¶
A class that holds RS485 specific settings which are supported on some platforms.
Added in version 3.0.
- __init__(rts_level_for_tx=True, rts_level_for_rx=False, loopback=False, delay_before_tx=None, delay_before_rx=None):
- Parameters:
rts_level_for_tx (bool) – RTS level for transmission
rts_level_for_rx (bool) – RTS level for reception
loopback (bool) – When set to
True
transmitted data is also received.delay_before_tx (float) – Delay after setting RTS but before transmission starts
delay_before_rx (float) – Delay after transmission ends and resetting RTS
- rts_level_for_tx¶
RTS level for transmission.
- rts_level_for_rx¶
RTS level for reception.
- loopback¶
When set to
True
transmitted data is also received.
- delay_before_tx¶
Delay after setting RTS but before transmission starts (seconds as float).
- delay_before_rx¶
Delay after transmission ends and resetting RTS (seconds as float).
- class rs485.RS485¶
A subclass that replaces the
Serial.write()
method with one that toggles RTS according to the RS485 settings.Usage:
ser = serial.rs485.RS485(...) ser.rs485_mode = serial.rs485.RS485Settings(...) ser.write(b'hello')
Warning
This may work unreliably on some serial ports (control signals not synchronized or delayed compared to data). Using delays may be unreliable (varying times, larger than expected) as the OS may not support very fine grained delays (no smaller than in the order of tens of milliseconds).
Note
Some implementations support this natively in the class
Serial
. Better performance can be expected when the native version is used.Note
The loopback property is ignored by this implementation. The actual behavior depends on the used hardware.
RFC 2217 Network ports¶
Warning
This implementation is currently in an experimental state. Use at your own risk.
- class rfc2217.Serial¶
This implements a RFC 2217 compatible client. Port names are URL in the form:
rfc2217://<host>:<port>[?<option>[&<option>]]
This class API is compatible to
Serial
with a few exceptions:write_timeout
is not implementedThe current implementation starts a thread that keeps reading from the (internal) socket. The thread is managed automatically by the
rfc2217.Serial
port object onopen()
/close()
. However it may be a problem for user applications that like to use select instead of threads.
Due to the nature of the network and protocol involved there are a few extra points to keep in mind:
All operations have an additional latency time.
Setting control lines (RTS/CTS) needs more time.
Reading the status lines (DSR/DTR etc.) returns a cached value. When that cache is updated depends entirely on the server. The server itself may implement a polling at a certain rate and quick changes may be invisible.
The network layer also has buffers. This means that
flush()
,reset_input_buffer()
andreset_output_buffer()
may work with additional delay. Likewisein_waiting
returns the size of the data arrived at the objects internal buffer and excludes any bytes in the network buffers or any server side buffer.Closing and immediately reopening the same port may fail due to time needed by the server to get ready again.
Not implemented yet / Possible problems with the implementation:
RFC 2217 flow control between client and server (objects internal buffer may eat all your memory when never read).
No authentication support (servers may not prompt for a password etc.)
No encryption.
Due to lack of authentication and encryption it is not suitable to use this client for connections across the internet and should only be used in controlled environments.
Added in version 2.5.
- class rfc2217.PortManager¶
This class provides helper functions for implementing RFC 2217 compatible servers.
Basically, it implements everything needed for the RFC 2217 protocol. It just does not open sockets and read/write to serial ports (though it changes other port settings). The user of this class must take care of the data transmission itself. The reason for that is, that this way, this class supports all programming models such as threads and select.
Usage examples can be found in the examples where two TCP/IP - serial converters are shown, one using threads (the single port server) and an other using select (the multi port server).
Note
Each new client connection must create a new instance as this object (and the RFC 2217 protocol) has internal state.
- __init__(serial_port, connection, debug_output=False)¶
- Parameters:
serial_port – a
Serial
instance that is managed.connection – an object implementing
write()
, used to write to the network.debug_output – enables debug messages: a
logging.Logger
instance or None.
Initializes the Manager and starts negotiating with client in Telnet and RFC 2217 protocol. The negotiation starts immediately so that the class should be instantiated in the moment the client connects.
The serial_port can be controlled by RFC 2217 commands. This object will modify the port settings (baud rate etc.) and control lines (RTS/DTR) send BREAK etc. when the corresponding commands are found by the
filter()
method.The connection object must implement a
write()
function. This function must ensure that data is written at once (no user data mixed in, i.e. it must be thread-safe). All data must be sent in its raw form (escape()
must not be used) as it is used to send Telnet and RFC 2217 control commands.For diagnostics of the connection or the implementation, debug_output can be set to an instance of a
logging.Logger
(e.g.logging.getLogger('rfc2217.server')
). The caller should configure the logger usingsetLevel
for the desired detail level of the logs.
- escape(data)¶
- Parameters:
data – data to be sent over the network.
- Returns:
data, escaped for Telnet/RFC 2217
A generator that escapes all data to be compatible with RFC 2217. Implementors of servers should use this function to process all data sent over the network.
The function returns a generator which can be used in
for
loops. It can be converted to bytes usingserial.to_bytes()
.
- filter(data)¶
- Parameters:
data – data read from the network, including Telnet and RFC 2217 controls.
- Returns:
data, free from Telnet and RFC 2217 controls.
A generator that filters and processes all data related to RFC 2217. Implementors of servers should use this function to process all data received from the network.
The function returns a generator which can be used in
for
loops. It can be converted to bytes usingserial.to_bytes()
.
- check_modem_lines(force_notification=False)¶
- Parameters:
force_notification – Set to false. Parameter is for internal use.
This function needs to be called periodically (e.g. every second) when the server wants to send NOTIFY_MODEMSTATE messages. This is required to support the client for reading CTS/DSR/RI/CD status lines.
The function reads the status line and issues the notifications automatically.
Added in version 2.5.
See also
RFC 2217 - Telnet Com Port Control Option
Exceptions¶
- exception serial.SerialException¶
Base class for serial port exceptions.
Changed in version 2.5: Now derives from
IOError
instead ofException
- exception serial.SerialTimeoutException¶
Exception that is raised on write timeouts.
Constants¶
Parity
- serial.PARITY_NONE¶
- serial.PARITY_EVEN¶
- serial.PARITY_ODD¶
- serial.PARITY_MARK¶
- serial.PARITY_SPACE¶
Stop bits
- serial.STOPBITS_ONE¶
- serial.STOPBITS_ONE_POINT_FIVE¶
- serial.STOPBITS_TWO¶
Note that 1.5 stop bits are not supported on POSIX. It will fall back to 2 stop bits.
Byte size
- serial.FIVEBITS¶
- serial.SIXBITS¶
- serial.SEVENBITS¶
- serial.EIGHTBITS¶
Others
Default control characters (instances of bytes
for Python 3.0+) for
software flow control:
- serial.XON¶
- serial.XOFF¶
Module version:
- serial.VERSION¶
A string indicating the pySerial version, such as
3.0
.Added in version 2.3.
Module functions and attributes¶
- serial.device(number)¶
Changed in version 3.0: removed, use
serial.tools.list_ports
instead
- serial.serial_for_url(url, \*args, \*\*kwargs)¶
- Parameters:
url – Device name, number or URL
do_not_open – When set to true, the serial port is not opened.
- Returns:
an instance of
Serial
or a compatible object.
Get a native or a RFC 2217 implementation of the Serial class, depending on port/url. This factory function is useful when an application wants to support both, local ports and remote ports. There is also support for other types, see URL section.
The port is not opened when a keyword parameter called do_not_open is given and true, by default it is opened.
Added in version 2.5.
- serial.protocol_handler_packages¶
This attribute is a list of package names (strings) that is searched for protocol handlers.
e.g. we want to support a URL
foobar://
. A modulemy_handlers.protocol_foobar
is provided by the user:serial.protocol_handler_packages.append("my_handlers") s = serial.serial_for_url("foobar://")
For an URL starting with
XY://
is the functionserial_for_url()
attempts to importPACKAGE.protocol_XY
with each candidate forPACKAGE
from this list.Added in version 2.6.
- serial.to_bytes(sequence)¶
- Parameters:
sequence – bytes, bytearray or memoryview
- Returns:
an instance of
bytes
Convert a sequence to a
bytes
type. This is used to write code that is compatible to Python 2.x and 3.x.In Python versions prior 3.x,
bytes
is a subclass of str. They convertstr([17])
to'[17]'
instead of'\x11'
so a simplebytes(sequence)
doesn’t work for all versions of Python.This function is used internally and in the unit tests.
Added in version 2.5.
- serial.iterbytes(sequence)¶
- Parameters:
sequence – bytes, bytearray or memoryview
- Returns:
a generator that yields bytes
Some versions of Python (3.x) would return integers instead of bytes when looping over an instance of
bytes
. This helper function ensures that bytes are returned.Added in version 3.0.
Threading¶
Added in version 3.0.
Warning
This implementation is currently in an experimental state. Use at your own risk.
This module provides classes to simplify working with threads and protocols.
- class serial.threaded.Protocol¶
Protocol as used by the
ReaderThread
. This base class provides empty implementations of all methods.- connection_made(transport)¶
- Parameters:
transport – instance used to write to serial port.
Called when reader thread is started.
- data_received(data)¶
- Parameters:
data (bytes) – received bytes
Called with snippets received from the serial port.
- connection_lost(exc)¶
- Parameters:
exc – Exception if connection was terminated by error else
None
Called when the serial port is closed or the reader loop terminated otherwise.
- class serial.threaded.Packetizer(Protocol)¶
Read binary packets from serial port. Packets are expected to be terminated with a
TERMINATOR
byte (null byte by default).The class also keeps track of the transport.
- TERMINATOR = b'\\0'
- __init__()¶
- connection_made(transport)¶
Stores transport.
- connection_lost(exc)¶
Forgets transport.
- data_received(data)¶
- Parameters:
data (bytes) – partial received data
Buffer received data and search for
TERMINATOR
, when found, callhandle_packet()
.
- handle_packet(packet)¶
- Parameters:
packet (bytes) – a packet as defined by
TERMINATOR
Process packets - to be overridden by subclassing.
- class serial.threaded.LineReader(Packetizer)¶
Read and write (Unicode) lines from/to serial port. The encoding is applied.
- TERMINATOR = b'\\r\\n'
Line ending.
- ENCODING = 'utf-8'
Encoding of the send and received data.
- UNICODE_HANDLING = 'replace'
Unicode error handly policy.
- handle_packet(packet)¶
- Parameters:
packet (bytes) – a packet as defined by
TERMINATOR
In this case it will be a line, calls
handle_line()
after applying theENCODING
.
- handle_line(line)¶
- Parameters:
line (str) – Unicode string with one line (excluding line terminator)
Process one line - to be overridden by subclassing.
- write_line(text)¶
- Parameters:
text (str) – Unicode string with one line (excluding line terminator)
Write text to the transport. text is expected to be a Unicode string and the encoding is applied before sending and also the
TERMINATOR
(new line) is appended.
- class serial.threaded.ReaderThread(threading.Thread)¶
Implement a serial port read loop and dispatch to a Protocol instance (like the
asyncio.Protocol
) but do it with threads.Calls to
close()
will close the serial port but it is also possible to juststop()
this thread and continue to use the serial port instance otherwise.- __init__(serial_instance, protocol_factory)¶
- Parameters:
serial_instance – serial port instance (opened) to be used.
protocol_factory – a callable that returns a Protocol instance
Initialize thread.
Note that the
serial_instance
‘s timeout is set to one second! Other settings are not changed.
- stop()¶
Stop the reader thread.
- run()¶
The actual reader loop driven by the thread. It calls
Protocol.connection_made()
, reads from the serial port callingProtocol.data_received()
and finally callsProtocol.connection_lost()
whenclose()
is called or an error occurs.
- write(data)¶
- Parameters:
data (bytes) – data to write
Thread safe writing (uses lock).
- connect()¶
Wait until connection is set up and return the transport and protocol instances.
This class can be used as context manager, in this case it starts the thread and connects automatically. The serial port is closed when the context is left.
- __enter__()¶
- Returns:
protocol
Connect and return protocol instance.
- __exit__(exc_type, exc_val, exc_tb)¶
Closes serial port.
Example:
class PrintLines(LineReader):
def connection_made(self, transport):
super(PrintLines, self).connection_made(transport)
sys.stdout.write('port opened\n')
self.write_line('hello world')
def handle_line(self, data):
sys.stdout.write('line received: {}\n'.format(repr(data)))
def connection_lost(self, exc):
if exc:
traceback.print_exc(exc)
sys.stdout.write('port closed\n')
ser = serial.serial_for_url('loop://', baudrate=115200, timeout=1)
with ReaderThread(ser, PrintLines) as protocol:
protocol.write_line('hello')
time.sleep(2)
asyncio¶
asyncio
was introduced with Python 3.4. Experimental support for pySerial
is provided via a separate distribution pyserial-asyncio.
It is currently under development, see: