pySerial -------- This module capsulates the access for the serial port. It provides backends for standard Python running on Windows, Linux, BSD (possibly any POSIX compilant system) and Jython. The module named "serial" automaticaly selects the appropriate backend. It is released under a free software license, see LICENSE.txt for more details. Project Homepage: pyserial.sourceforge.net (C) 2001-2004 Chris Liechti Features -------- - same class based interface on all supported platforms - access to the port settings trough Python 2.2 properties - port numbering starts at zero, no need to know the platform dependant port name in the user program - port name can be specified if access through numbering is inappropriate - support for different bytesizes, stopbits, parity and flow control with RTS/CTS and/or Xon/Xoff - working with or without receive timeout, blocking or non-blocking - file like API with "read" and "write" ("readline" etc. also supported) - The files in this package are 100% pure Python. They depend on non standard but common packages on Windows (win32all) and Jython (JavaComm). POSIX (Linux, BSD) uses only modules from the standard Python distribution) - The port is set up for binary transmission. No NULL byte stripping, CR-LF translation etc. (which are many times enabled for POSIX.) This makes this module universally useful. Requirements ------------ - Python 2.2 or newer - win32all extensions on Windows - "Java Communications" (JavaComm) extension for Java/Jython Installation ------------ Extract files from the archive, open a shell/console in that directory and let Distutils do the rest: "python setup.py install" The files get installed in the "Lib/site-packages" directory. There is also a Windows installer, but for developers it may be interesting to get the source archive anyway, because it contains examples and the readme. Do also have a look at the example files in the examples directory in the source distribution or online in CVS repository. Serial to USB adapters ---------------------- Such adapters are reported to work under Mac OSX and Windows. They are mapped to a normal COM port under Windows, but on Mac OSX and other platforms they have special device names. Mac OSX: "/dev/[cu|tty].USAP.1" e.g. "/dev/cu.USA19QW11P1.1" Linux: "/dev/usb/ttyUSB[n]" or "/dev/ttyUSB[n]" first for for RedHat, second form for Debian. e.g. "/dev/usb/ttyUSB0" Either use these names for the serial ports or create a link to the common device names like "ln -s /dev/cu.USA19QW11P1.1 /dev/cuaa0" or "ln -s /dev/usb/ttyUSB0 /dev/ttyS4" etc. But be aware that the (USB) device file disappears as soon as you unplug the USB adapter. Short introduction ------------------ Open port 0 at "9600,8,N,1", no timeout >>> import serial >>> ser = serial.Serial(0) #open first serial port >>> print ser.portstr #check which port was realy used >>> ser.write("hello") #write a string >>> ser.close() #close port Open named port at "19200,8,N,1", 1s timeout >>> ser = serial.Serial('/dev/ttyS1', 19200, timeout=1) >>> x = ser.read() #read one byte >>> s = ser.read(10) #read up to ten bytes (timeout) >>> line = ser.readline() #read a '\n' terminated line >>> ser.close() Open second port at "38400,8,E,1", non blocking HW handshaking >>> ser = serial.Serial(1, 38400, timeout=0, ... parity=serial.PARITY_EVEN, rtscts=1) >>> s = ser.read(100) #read up to one hunded bytes ... #or as much is in the buffer Get a Serial instance and configure/open it later >>> ser = serial.Serial() >>> ser.baudrate = 19200 >>> ser.port = 0 >>> ser Serial(port='COM1', baudrate=19200, bytesize=8, parity='N', stopbits=1, timeout=None, xonxoff=0, rtscts=0) >>> ser.open() >>> ser.isOpen() True >>> ser.close() >>> ser.isOpen() False Be carefully 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. Parameters for the Serial class ------------------------------- ser = serial.Serial( port=None, #number of device, numbering starts at #zero. if everything fails, the user #can specify a device string, note #that this isn't portable anymore #if no port is specified an unconfigured #an closed serial port object is created baudrate=9600, #baudrate bytesize=EIGHTBITS, #number of databits parity=PARITY_NONE, #enable parity checking stopbits=STOPBITS_ONE, #number of stopbits timeout=None, #set a timeout value, None to wait forever xonxoff=0, #enable software flow control rtscts=0, #enable RTS/CTS flow control writeTimeout=None, #set a timeout for writes ) The port is immediately opened on object creation, if a port is given. It is not opened if port is None. Options for read timeout: timeout=None #wait forever timeout=0 #non-blocking mode (return immediately on read) timeout=x #set timeout to x seconds (float allowed) Options for write timeout: writeTimeout=x #will rise a SerialTimeoutException if the data #cannot be sent in x seconds Methods of Serial instances --------------------------- open() #open port close() #close port immediately setBaudrate(baudrate) #change baudarte on an open port inWaiting() #return the number of chars in the receive buffer read(size=1) #read "size" characters write(s) #write the string s to the port flushInput() #flush input buffer, discarding all it's contents flushOutput() #flush output buffer, abort output sendBreak() #send break condition setRTS(level=1) #set RTS line to specified logic level setDTR(level=1) #set DTR line to specified logic level getCTS() #return the state of the CTS line getDSR() #return the state of the DSR line getRI() #return the state of the RI line getCD() #return the state of the CD line Attributes of Serial instances ------------------------------ Read Only: portstr #device name BAUDRATES #list of valid baudrates BYTESIZES #list of valid byte sizes PARITIES #list of valid parities STOPBITS #list of valid stop bit widths New values can be assigned to the following attribues, the port will be reconfigured, even if it's opened at that time (port will be closed and reopened to apply the changes): port #port name/number as set by the user baudrate #current baudrate setting bytesize #bytesize in bits parity #parity setting stopbits #stop bit with (1,2) timeout #read timeout setting xonxoff #if Xon/Xoff flow control is enabled rtscts #if hardware flow control is enabled writeTimeout #write timeout setting These attribues also have corresponding getX and setXX methods. Exceptions ---------- serial.SerialException Constants --------- parity: serial.PARITY_NONE serial.PARITY_EVEN serial.PARITY_ODD stopbits: serial.STOPBITS_ONE serial.STOPBITS_TWO bytesize: serial.FIVEBITS serial.SIXBITS serial.SEVENBITS serial.EIGHTBITS Xon/Xoff characters: serial.XON serial.XOFF Tips & Tricks ------------- - Some protocols need CR LF ("\r\n") as line terminator, not just LF ("\n"). Telephone modems with the AT command set are an example of this behaviour. - Scanning for available serial ports is possible with more or less success on some platforms. Look at the tools from Roger Binns: http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/bitpim/comscan/ - When packaging a project with py2exe, it will likely print a warning about missing modules 'javax.comm'. This warning is uncritical as the module is used in the Jython implementation that is not used but packaged. It can be avoided with: setup(... options = {'py2exe': {'excludes': ['javax.comm']}}) See also setup_demo.py in the examples. References ---------- - Python: http://www.python.org - Jython: http://www.jython.org - win32all: http://starship.python.net/crew/mhammond/ and http://www.activestate.com/Products/ActivePython/win32all.html - Java@IBM http://www-106.ibm.com/developerworks/java/jdk/ (JavaComm links are on the download page for the respective platform jdk) - Java@SUN http://java.sun.com/products/