树莓派+Python+pyserial 2.7实现串口通信
手上有个CCD Camera(Barcode Reader/Scanner Module)，它是通过RS232通信的，用RS232转USB的转接线连接树莓派，即可完成硬件连接。对于串口通信，可以通过pyserial实现。
首先，安装pyserial：
从https://pypi.python.org/pypi/pyserial下载最新版本的安装包，再通过下面的命令完成安装：
tar zxvf pyserial-2.7.tar.gz cd pyserial-2.7 python setup.py install
通过命令lsusb查看串口是否存在：
通过命令python -m serial.tools.list_ports可以查看大可用的端口：
测试通信：
通过以上的准备后，就可以写一个简单的Python程式来实现串口通信：
import serial
from time import sleep
ser = serial.Serial('/dev/ttyUSB0', 9600, timeout=0.5)
def recv(serial):
data
while True:
data =serial.read(30)
if data == '':
continue
else:
break
sleep(0.02)
return data
while True:
data =recv(ser)
ser.write(data)
来自官网的Sample(wxTerminal.py)也很不错，可以通过UI选择和配置端口：
#!/usr/bin/env python
# generated by wxGlade 0.3.1 on Fri Oct 03 23:23:45 2003
#from wxPython.wx import *
import wx
import wxSerialConfigDialog
import serial
import threading
#----------------------------------------------------------------------
# Create an own event type, so that GUI updates can be delegated
# this is required as on some platforms only the main thread can
# access the GUI without crashing. wxMutexGuiEnter/wxMutexGuiLeave
# could be used too, but an event is more elegant.
SERIALRX = wx.NewEventType()
# bind to serial data receive events
EVT_SERIALRX = wx.PyEventBinder(SERIALRX, 0)
class SerialRxEvent(wx.PyCommandEvent):
eventType = SERIALRX
def __init__(self, windowID, data):
wx.PyCommandEvent.__init__(self, self.eventType, windowID)
self.data = data
def Clone(self):
self.__class__(self.GetId(), self.data)
#----------------------------------------------------------------------
ID_CLEAR = wx.NewId()
ID_SAVEAS = wx.NewId()
ID_SETTINGS = wx.NewId()
ID_TERM = wx.NewId()
ID_EXIT = wx.NewId()
NEWLINE_CR = 0
NEWLINE_LF = 1
NEWLINE_CRLF = 2
class TerminalSetup:
"""Placeholder for various terminal settings. Used to pass the
options to the TerminalSettingsDialog."""
def __init__(self):
self.echo = False
self.unprintable = False
self.newline = NEWLINE_CRLF
class TerminalSettingsDialog(wx.Dialog):
"""Simple dialog with common terminal settings like echo, newline mode."""
def __init__(self, *args, **kwds):
self.settings = kwds['settings']
del kwds['settings']
# begin wxGlade: TerminalSettingsDialog.__init__
kwds["style"] = wx.DEFAULT_DIALOG_STYLE
wx.Dialog.__init__(self, *args, **kwds)
self.checkbox_echo = wx.CheckBox(self, -1, "Local Echo")
self.checkbox_unprintable = wx.CheckBox(self, -1, "Show unprintable characters")
self.radio_box_newline = wx.RadioBox(self, -1, "Newline Handling", choices=["CR only", "LF only", "CR+LF"], majorDimension=0, style=wx.RA_SPECIFY_ROWS)
self.button_ok = wx.Button(self, -1, "OK")
self.button_cancel = wx.Button(self, -1, "Cancel")
self.__set_properties()
self.__do_layout()
# end wxGlade
self.__attach_events()
self.checkbox_echo.SetValue(self.settings.echo)
self.checkbox_unprintable.SetValue(self.settings.unprintable)
self.radio_box_newline.SetSelection(self.settings.newline)
def __set_properties(self):
# begin wxGlade: TerminalSettingsDialog.__set_properties
self.SetTitle("Terminal Settings")
self.radio_box_newline.SetSelection(0)
self.button_ok.SetDefault()
# end wxGlade
def __do_layout(self):
# begin wxGlade: TerminalSettingsDialog.__do_layout
sizer_2 = wx.BoxSizer(wx.VERTICAL)
sizer_3 = wx.BoxSizer(wx.HORIZONTAL)
sizer_4 = wx.StaticBoxSizer(wx.StaticBox(self, -1, "Input/Output"), wx.VERTICAL)
sizer_4.Add(self.checkbox_echo, 0, wx.ALL, 4)
sizer_4.Add(self.checkbox_unprintable, 0, wx.ALL, 4)
sizer_4.Add(self.radio_box_newline, 0, 0, 0)
sizer_2.Add(sizer_4, 0, wx.EXPAND, 0)
sizer_3.Add(self.button_ok, 0, 0, 0)
sizer_3.Add(self.button_cancel, 0, 0, 0)
sizer_2.Add(sizer_3, 0, wx.ALL|wx.ALIGN_RIGHT, 4)
self.SetAutoLayout(1)
self.SetSizer(sizer_2)
sizer_2.Fit(self)
sizer_2.SetSizeHints(self)
self.Layout()
# end wxGlade
def __attach_events(self):
self.Bind(wx.EVT_BUTTON, self.OnOK, id = self.button_ok.GetId())
self.Bind(wx.EVT_BUTTON, self.OnCancel, id = self.button_cancel.GetId())
def OnOK(self, events):
"""Update data wil new values and close dialog."""
self.settings.echo = self.checkbox_echo.GetValue()
self.settings.unprintable = self.checkbox_unprintable.GetValue()
self.settings.newline = self.radio_box_newline.GetSelection()
self.EndModal(wx.ID_OK)
def OnCancel(self, events):
"""Do not update data but close dialog."""
self.EndModal(wx.ID_CANCEL)
# end of class TerminalSettingsDialog
class TerminalFrame(wx.Frame):
"""Simple terminal program for wxPython"""
def __init__(self, *args, **kwds):
self.serial = serial.Serial()
self.serial.timeout = 0.5 #make sure that the alive event can be checked from time to time
self.settings = TerminalSetup() #placeholder for the settings
self.thread = None
self.alive = threading.Event()
# begin wxGlade: TerminalFrame.__init__
kwds["style"] = wx.DEFAULT_FRAME_STYLE
wx.Frame.__init__(self, *args, **kwds)
self.text_ctrl_output = wx.TextCtrl(self, -1, "", style=wx.TE_MULTILINE|wx.TE_READONLY)
# Menu Bar
self.frame_terminal_menubar = wx.MenuBar()
self.SetMenuBar(self.frame_terminal_menubar)
wxglade_tmp_menu = wx.Menu()
wxglade_tmp_menu.Append(ID_CLEAR, "&Clear", "", wx.ITEM_NORMAL)
wxglade_tmp_menu.Append(ID_SAVEAS, "&Save Text As...", "", wx.ITEM_NORMAL)
wxglade_tmp_menu.AppendSeparator()
wxglade_tmp_menu.Append(ID_SETTINGS, "&Port Settings...", "", wx.ITEM_NORMAL)
wxglade_tmp_menu.Append(ID_TERM, "&Terminal Settings...", "", wx.ITEM_NORMAL)
wxglade_tmp_menu.AppendSeparator()
wxglade_tmp_menu.Append(ID_EXIT, "&Exit", "", wx.ITEM_NORMAL)
self.frame_terminal_menubar.Append(wxglade_tmp_menu, "&File")
# Menu Bar end
self.__set_properties()
self.__do_layout()
# end wxGlade
self.__attach_events() #register events
self.OnPortSettings(None) #call setup dialog on startup, opens port
if not self.alive.isSet():
self.Close()
def StartThread(self):
"""Start the receiver thread"""
self.thread = threading.Thread(target=self.ComPortThread)
self.thread.setDaemon(1)
self.alive.set()
self.thread.start()
def StopThread(self):
"""Stop the receiver thread, wait util it's finished."""
if self.thread is not None:
self.alive.clear() #clear alive event for thread
self.thread.join() #wait until thread has finished
self.thread = None
def __set_properties(self):
# begin wxGlade: TerminalFrame.__set_properties
self.SetTitle("Serial Terminal")
self.SetSize((546, 383))
# end wxGlade
def __do_layout(self):
# begin wxGlade: TerminalFrame.__do_layout
sizer_1 = wx.BoxSizer(wx.VERTICAL)
sizer_1.Add(self.text_ctrl_output, 1, wx.EXPAND, 0)
self.SetAutoLayout(1)
self.SetSizer(sizer_1)
self.Layout()
# end wxGlade
def __attach_events(self):
#register events at the controls
self.Bind(wx.EVT_MENU, self.OnClear, id = ID_CLEAR)
self.Bind(wx.EVT_MENU, self.OnSaveAs, id = ID_SAVEAS)
self.Bind(wx.EVT_MENU, self.OnExit, id = ID_EXIT)
self.Bind(wx.EVT_MENU, self.OnPortSettings, id = ID_SETTINGS)
self.Bind(wx.EVT_MENU, self.OnTermSettings, id = ID_TERM)
self.text_ctrl_output.Bind(wx.EVT_CHAR, self.OnKey)
self.Bind(EVT_SERIALRX, self.OnSerialRead)
self.Bind(wx.EVT_CLOSE, self.OnClose)
def OnExit(self, event):
"""Menu point Exit"""
self.Close()
def OnClose(self, event):
"""Called on application shutdown."""
self.StopThread() #stop reader thread
self.serial.close() #cleanup
self.Destroy() #close windows, exit app
def OnSaveAs(self, event):
"""Save contents of output window."""
filename = None
dlg = wx.FileDialog(None, "Save Text As...", ".", "", "Text File|*.txt|All Files|*", wx.SAVE)
if dlg.ShowModal() == wx.ID_OK:
filename = dlg.GetPath()
dlg.Destroy()
if filename is not None:
f = file(filename, 'w')
text = self.text_ctrl_output.GetValue()
if type(text) == unicode:
text = text.encode("latin1") #hm, is that a good asumption?
f.write(text)
f.close()
def OnClear(self, event):
"""Clear contents of output window."""
self.text_ctrl_output.Clear()
def OnPortSettings(self, event=None):
"""Show the portsettings dialog. The reader thread is stopped for the
settings change."""
if event is not None: #will be none when called on startup
self.StopThread()
self.serial.close()
ok = False
while not ok:
dialog_serial_cfg = wxSerialConfigDialog.SerialConfigDialog(None, -1, "",
show=wxSerialConfigDialog.SHOW_BAUDRATE|wxSerialConfigDialog.SHOW_FORMAT|wxSerialConfigDialog.SHOW_FLOW,
serial=self.serial
)
result = dialog_serial_cfg.ShowModal()
dialog_serial_cfg.Destroy()
#open port if not called on startup, open it on startup and OK too
if result == wx.ID_OK or event is not None:
try:
self.serial.open()
except serial.SerialException, e:
dlg = wx.MessageDialog(None, str(e), "Serial Port Error", wx.OK | wx.ICON_ERROR)
dlg.ShowModal()
dlg.Destroy()
else:
self.StartThread()
self.SetTitle("Serial Terminal on %s [%s, %s%s%s%s%s]" % (
self.serial.portstr,
self.serial.baudrate,
self.serial.bytesize,
self.serial.parity,
self.serial.stopbits,
self.serial.rtscts and ' RTS/CTS' or '',
self.serial.xonxoff and ' Xon/Xoff' or '',
)
)
ok = True
else:
#on startup, dialog aborted
self.alive.clear()
ok = True
def OnTermSettings(self, event):
"""Menu point Terminal Settings. Show the settings dialog
with the current terminal settings"""
dialog = TerminalSettingsDialog(None, -1, "", settings=self.settings)
result = dialog.ShowModal()
dialog.Destroy()
def OnKey(self, event):
"""Key event handler. if the key is in the ASCII range, write it to the serial port.
Newline handling and local echo is also done here."""
code = event.GetKeyCode()
if code < 256: #is it printable?
if code == 13: #is it a newline? (check for CR which is the RETURN key)
if self.settings.echo: #do echo if needed
self.text_ctrl_output.AppendText('\n')
if self.settings.newline == NEWLINE_CR:
self.serial.write('\r') #send CR
elif self.settings.newline == NEWLINE_LF:
self.serial.write('\n') #send LF
elif self.settings.newline == NEWLINE_CRLF:
self.serial.write('\r\n') #send CR+LF
else:
char = chr(code)
if self.settings.echo: #do echo if needed
self.text_ctrl_output.WriteText(char)
self.serial.write(char) #send the charcater
else:
print "Extra Key:", code
def OnSerialRead(self, event):
"""Handle input from the serial port."""
text = event.data
if self.settings.unprintable:
text = ''.join([(c >= ' ') and c or '<%d>' % ord(c) for c in text])
self.text_ctrl_output.AppendText(text)
def ComPortThread(self):
"""Thread that handles the incomming traffic. Does the basic input
transformation (newlines) and generates an SerialRxEvent"""
while self.alive.isSet(): #loop while alive event is true
text = self.serial.read(1) #read one, with timout
if text: #check if not timeout
n = self.serial.inWaiting() #look if there is more to read
if n:
text = text + self.serial.read(n) #get it
#newline transformation
if self.settings.newline == NEWLINE_CR:
text = text.replace('\r', '\n')
elif self.settings.newline == NEWLINE_LF:
pass
elif self.settings.newline == NEWLINE_CRLF:
text = text.replace('\r\n', '\n')
event = SerialRxEvent(self.GetId(), text)
self.GetEventHandler().AddPendingEvent(event)
#~ self.OnSerialRead(text) #output text in window
# end of class TerminalFrame
class MyApp(wx.App):
def OnInit(self):
wx.InitAllImageHandlers()
frame_terminal = TerminalFrame(None, -1, "")
self.SetTopWindow(frame_terminal)
frame_terminal.Show(1)
return 1
# end of class MyApp
if __name__ == "__main__":
app = MyApp(0)
app.MainLoop()