Serial port python examples

Short introduction¶

Open port at “38400,8,E,1”, non blocking HW handshaking:

>>> ser = serial.Serial('COM3', 38400, timeout=0, . parity=serial.PARITY_EVEN, rtscts=1) >>> s = ser.read(100) # read up to one hundred bytes . # or as much is in the buffer 

Configuring ports later¶

Get a Serial instance and configure/open it later:

>>> ser = serial.Serial() >>> ser.baudrate = 19200 >>> ser.port = 'COM1' >>> ser Serial(port='COM1', baudrate=19200, bytesize=8, parity='N', stopbits=1, timeout=None, xonxoff=0, rtscts=0) >>> ser.open() >>> ser.is_open True >>> ser.close() >>> ser.is_open False 

with serial.Serial() as ser: ser.baudrate = 19200 ser.port = 'COM1' ser.open() ser.write(b'hello') 

Readline¶

Be careful when using readline() . Do specify a timeout when opening the serial port otherwise it could block forever if no newline character is received. Also note that readlines() only works with a timeout. readlines() depends on having a timeout and interprets that as EOF (end of file). It raises an exception if the port is not opened correctly.

Do also have a look at the example files in the examples directory in the source distribution or online.

The eol parameter for readline() is no longer supported when pySerial is run with newer Python versions (V2.6+) where the module io is available.

EOL¶

To specify the EOL character for readline() or to use universal newline mode, it is advised to use io.TextIOWrapper:

import serial import io ser = serial.serial_for_url('loop://', timeout=1) sio = io.TextIOWrapper(io.BufferedRWPair(ser, ser)) sio.write(unicode("hello\n")) sio.flush() # it is buffering. required to get the data out *now* hello = sio.readline() print(hello == unicode("hello\n")) 

Testing ports¶

Listing ports¶

python -m serial.tools.list_ports will print a list of available ports. It is also possible to add a regexp as first argument and the list will only include entries that matched.

The enumeration may not work on all operating systems. It may be incomplete, list unavailable ports or may lack detailed descriptions of the ports.

Accessing ports¶

pySerial includes a small console based terminal program called serial.tools.miniterm . It can be started with python -m serial.tools.miniterm (use option -h to get a listing of all options).

© Copyright 2001-2020, Chris Liechti Revision 0e763474 .

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Examples¶

Miniterm is now available as module instead of example. see serial.tools.miniterm for details.

miniterm.py The miniterm program. setup-miniterm-py2exe.py This is a py2exe setup script for Windows. It can be used to create a standalone miniterm.exe .

TCP/IP — serial bridge¶

This program opens a TCP/IP port. When a connection is made to that port (e.g. with telnet) it forwards all data to the serial port and vice versa.

This example only exports a raw socket connection. The next example below gives the client much more control over the remote serial port.

• The serial port settings are set on the command line when starting the program.
• There is no possibility to change settings from remote.
• All data is passed through as-is.

usage: tcp_serial_redirect.py [-h] [-q] [--parity N,E,O,S,M>] [--rtscts] [--xonxoff] [--rts RTS] [--dtr DTR] [-P LOCALPORT] SERIALPORT [BAUDRATE] Simple Serial to Network (TCP/IP) redirector. positional arguments: SERIALPORT serial port name BAUDRATE set baud rate, default: 9600 optional arguments: -h, --help show this help message and exit -q, --quiet suppress non error messages serial port: --parity N,E,O,S,M> set parity, one of N E O S M>, default: N --rtscts enable RTS/CTS flow control (default off) --xonxoff enable software flow control (default off) --rts RTS set initial RTS line state (possible values: 0, 1) --dtr DTR set initial DTR line state (possible values: 0, 1) network settings: -P LOCALPORT, --localport LOCALPORT local TCP port NOTE: no security measures are implemented. Anyone can remotely connect to this service over the network. Only one connection at once is supported. When the connection is terminated it waits for the next connect. 

Single-port TCP/IP — serial bridge (RFC 2217)¶

Simple cross platform RFC 2217 serial port server. It uses threads and is portable (runs on POSIX, Windows, etc).

• The port settings and control lines (RTS/DTR) can be changed at any time using RFC 2217 requests. The status lines (DSR/CTS/RI/CD) are polled every second and notifications are sent to the client.
• Telnet character IAC (0xff) needs to be doubled in data stream. IAC followed by another value is interpreted as Telnet command sequence.
• Telnet negotiation commands are sent when connecting to the server.
• RTS/DTR are activated on client connect and deactivated on disconnect.
• Default port settings are set again when client disconnects.

usage: rfc2217_server.py [-h] [-p TCPPORT] [-v] SERIALPORT RFC 2217 Serial to Network (TCP/IP) redirector. positional arguments: SERIALPORT optional arguments: -h, --help show this help message and exit -p TCPPORT, --localport TCPPORT local TCP port, default: 2217 -v, --verbose print more diagnostic messages (option can be given multiple times) NOTE: no security measures are implemented. Anyone can remotely connect to this service over the network. Only one connection at once is supported. When the connection is terminated it waits for the next connect. 

rfc2217_server.py Main program. setup-rfc2217_server-py2exe.py This is a py2exe setup script for Windows. It can be used to create a standalone rfc2217_server.exe .

Multi-port TCP/IP — serial bridge (RFC 2217)¶

This example implements a TCP/IP to serial port service that works with multiple ports at once. It uses select, no threads, for the serial ports and the network sockets and therefore runs on POSIX systems only.

• Full control over the serial port with RFC 2217.
• Check existence of /tty/USB0. 8 . This is done every 5 seconds using os.path.exists .
• Send zeroconf announcements when port appears or disappears (uses python-avahi and dbus). Service name: _serial_port._tcp .
• Each serial port becomes available as one TCP/IP server. e.g. /dev/ttyUSB0 is reachable at :7000 .
• Single process for all ports and sockets (not per port).
• The script can be started as daemon.
• Logging to stdout or when run as daemon to syslog.
• Default port settings are set again when client disconnects.
• modem status lines (CTS/DSR/RI/CD) are not polled periodically and the server therefore does not send NOTIFY_MODEMSTATE on its own. However it responds to request from the client (i.e. use the poll_modem option in the URL when using a pySerial client.)

usage: port_publisher.py [options] Announce the existence of devices using zeroconf and provide a TCP/IP serial port gateway (implements RFC 2217). If running as daemon, write to syslog. Otherwise write to stdout. optional arguments: -h, --help show this help message and exit serial port settings: --ports-regex REGEX specify a regex to search against the serial devices and their descriptions (default: /dev/ttyUSB[0-9]+) network settings: --tcp-port PORT specify lowest TCP port number (default: 7000) daemon: -d, --daemon start as daemon --pidfile FILE specify a name for the PID file diagnostics: -o FILE, --logfile FILE write messages file instead of stdout -q, --quiet suppress most diagnostic messages -v, --verbose increase diagnostic messages NOTE: no security measures are implemented. Anyone can remotely connect to this service over the network. Only one connection at once, per port, is supported. When the connection is terminated, it waits for the next connect. 

• Copy the script port_publisher.py to /usr/local/bin .
• Copy the script port_publisher.sh to /etc/init.d .
• Add links to the runlevels using update-rc.d port_publisher.sh defaults 99
• That’s it 🙂 the service will be started on next reboot. Alternatively run invoke-rc.d port_publisher.sh start as root.

New in version 2.5: new example

port_publisher.py Multi-port TCP/IP-serial converter (RFC 2217) for POSIX environments. port_publisher.sh Example init.d script.

wxPython examples¶

A simple terminal application for wxPython and a flexible serial port configuration dialog are shown here.

wxTerminal.py A simple terminal application. Note that the length of the buffer is limited by wx and it may suddenly stop displaying new input. wxTerminal.wxg A wxGlade design file for the terminal application. wxSerialConfigDialog.py A flexible serial port configuration dialog. wxSerialConfigDialog.wxg The wxGlade design file for the configuration dialog. setup-wxTerminal-py2exe.py A py2exe setup script to package the terminal application.

Unit tests¶

The project uses a number of unit test to verify the functionality. They all need a loop back connector. The scripts itself contain more information. All test scripts are contained in the directory test .

The unit tests are performed on port loop:// unless a different device name or URL is given on the command line ( sys.argv[1] ). e.g. to run the test on an attached USB-serial converter hwgrep://USB could be used or the actual name such as /dev/ttyUSB0 or COM1 (depending on platform).

run_all_tests.py Collect all tests from all test* files and run them. By default, the loop:// device is used. test.py Basic tests (binary capabilities, timeout, control lines). test_advanced.py Test more advanced features (properties). test_high_load.py Tests involving sending a lot of data. test_readline.py Tests involving readline . test_iolib.py Tests involving the io library. Only available for Python 2.6 and newer. test_url.py Tests involving the URL feature.

© Copyright 2001-2020, Chris Liechti Revision 31fa4807 .

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Short introduction¶

Open port at “38400,8,E,1”, non blocking HW handshaking:

>>> ser = serial.Serial('COM3', 38400, timeout=0, . parity=serial.PARITY_EVEN, rtscts=1) >>> s = ser.read(100) # read up to one hundred bytes . # or as much is in the buffer 

Configuring ports later¶

Get a Serial instance and configure/open it later:

>>> ser = serial.Serial() >>> ser.baudrate = 19200 >>> ser.port = 'COM1' >>> ser Serial(port='COM1', baudrate=19200, bytesize=8, parity='N', stopbits=1, timeout=None, xonxoff=0, rtscts=0) >>> ser.open() >>> ser.is_open True >>> ser.close() >>> ser.is_open False 

with serial.Serial() as ser: ser.baudrate = 19200 ser.port = 'COM1' ser.open() ser.write(b'hello') 

Readline¶

readline() reads up to one line, including the \n at the end. Be careful when using readline() . Do specify a timeout when opening the serial port otherwise it could block forever if no newline character is received. If the \n is missing in the return value, it returned on timeout.

readlines() tries to read “all” lines which is not well defined for a serial port that is still open. Therefore readlines() depends on having a timeout on the port and interprets that as EOF (end of file). It raises an exception if the port is not opened correctly. The returned list of lines do not include the \n .

Both functions call read() to get their data and the serial port timeout is acting on this function. Therefore the effective timeout, especially for readlines() , can be much larger.

Do also have a look at the example files in the examples directory in the source distribution or online.

The eol parameter for readline() is no longer supported when pySerial is run with newer Python versions (V2.6+) where the module io is available.

EOL¶

To specify the EOL character for readline() or to use universal newline mode, it is advised to use io.TextIOWrapper:

import serial import io ser = serial.serial_for_url('loop://', timeout=1) sio = io.TextIOWrapper(io.BufferedRWPair(ser, ser)) sio.write(unicode("hello\n")) sio.flush() # it is buffering. required to get the data out *now* hello = sio.readline() print(hello == unicode("hello\n")) 

Testing ports¶

Listing ports¶

python -m serial.tools.list_ports will print a list of available ports. It is also possible to add a regexp as first argument and the list will only include entries that matched.

The enumeration may not work on all operating systems. It may be incomplete, list unavailable ports or may lack detailed descriptions of the ports.

Accessing ports¶

pySerial includes a small console based terminal program called serial.tools.miniterm . It can be started with python -m serial.tools.miniterm (use option -h to get a listing of all options).

© Copyright 2001-2020, Chris Liechti Revision 31fa4807 .

Versions latest stable Downloads pdf html epub On Read the Docs Project Home Builds Free document hosting provided by Read the Docs.

Источник