樹莓派+Python+pyserial 2.7實現串列埠通訊
手上有個CCD Camera(Barcode Reader/Scanner Module),它是通過RS232通訊的,用RS232轉USB的轉接線連線樹莓派,即可完成硬體連線。對於串列埠通訊,可以通過pyserial實現。
首先,安裝pyserial:
tar zxvf pyserial-2.7.tar.gz
cd pyserial-2.7
python setup.py install
通過命令lsusb檢視串列埠是否存在:
通過命令python -m serial.tools.list_ports可以檢視大可用的埠:
測試通訊:
通過以上的準備後,就可以寫一個簡單的Python程式來實現串列埠通訊:
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)
來自官網的Sample(wxTerminal.py)也很不錯,可以通過UI選擇和配置埠:
#!/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()
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