133 lines
5.6 KiB
Python
133 lines
5.6 KiB
Python
# This is a simple serial port terminal demo.
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#
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# Its primary purpose is to demonstrate the native serial port access offered via
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# win32file.
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# It uses 3 threads:
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# - The main thread, which cranks up the other 2 threads, then simply waits for them to exit.
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# - The user-input thread - blocks waiting for a keyboard character, and when found sends it
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# out the COM port. If the character is Ctrl+C, it stops, signalling the COM port thread to stop.
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# - The COM port thread is simply listening for input on the COM port, and prints it to the screen.
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# This demo uses userlapped IO, so that none of the read or write operations actually block (however,
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# in this sample, the very next thing we do _is_ block - so it shows off the concepts even though it
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# doesnt exploit them.
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from win32file import * # The base COM port and file IO functions.
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from win32event import * # We use events and the WaitFor[Multiple]Objects functions.
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import win32con # constants.
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import msvcrt # For the getch() function.
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import threading
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import sys
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def FindModem():
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# Snoop over the comports, seeing if it is likely we have a modem.
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for i in range(1,5):
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port = "COM%d" % (i,)
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try:
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handle = CreateFile(port,
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win32con.GENERIC_READ | win32con.GENERIC_WRITE,
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0, # exclusive access
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None, # no security
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win32con.OPEN_EXISTING,
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win32con.FILE_ATTRIBUTE_NORMAL,
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None)
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# It appears that an available COM port will always success here,
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# just return 0 for the status flags. We only care that it has _any_ status
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# flags (and therefore probably a real modem)
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if GetCommModemStatus(handle) != 0:
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return port
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except error:
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pass # No port, or modem status failed.
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return None
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# A basic synchronous COM port file-like object
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class SerialTTY:
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def __init__(self, port):
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if type(port)==type(0):
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port = "COM%d" % (port,)
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self.handle = CreateFile(port,
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win32con.GENERIC_READ | win32con.GENERIC_WRITE,
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0, # exclusive access
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None, # no security
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win32con.OPEN_EXISTING,
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win32con.FILE_ATTRIBUTE_NORMAL | win32con.FILE_FLAG_OVERLAPPED,
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None)
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# Tell the port we want a notification on each char.
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SetCommMask(self.handle, EV_RXCHAR)
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# Setup a 4k buffer
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SetupComm(self.handle, 4096, 4096)
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# Remove anything that was there
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PurgeComm(self.handle, PURGE_TXABORT | PURGE_RXABORT | PURGE_TXCLEAR | PURGE_RXCLEAR )
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# Setup for overlapped IO.
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timeouts = 0xFFFFFFFF, 0, 1000, 0, 1000
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SetCommTimeouts(self.handle, timeouts)
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# Setup the connection info.
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dcb = GetCommState( self.handle )
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dcb.BaudRate = CBR_115200
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dcb.ByteSize = 8
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dcb.Parity = NOPARITY
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dcb.StopBits = ONESTOPBIT
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SetCommState(self.handle, dcb)
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print("Connected to %s at %s baud" % (port, dcb.BaudRate))
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def _UserInputReaderThread(self):
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overlapped = OVERLAPPED()
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overlapped.hEvent = CreateEvent(None, 1, 0, None)
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try:
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while 1:
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ch = msvcrt.getch()
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if ord(ch)==3:
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break
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WriteFile(self.handle, ch, overlapped)
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# Wait for the write to complete.
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WaitForSingleObject(overlapped.hEvent, INFINITE)
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finally:
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SetEvent(self.eventStop)
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def _ComPortThread(self):
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overlapped = OVERLAPPED()
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overlapped.hEvent = CreateEvent(None, 1, 0, None)
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while 1:
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# XXX - note we could _probably_ just use overlapped IO on the win32file.ReadFile() statement
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# XXX but this tests the COM stuff!
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rc, mask = WaitCommEvent(self.handle, overlapped)
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if rc == 0: # Character already ready!
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SetEvent(overlapped.hEvent)
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rc = WaitForMultipleObjects([overlapped.hEvent, self.eventStop], 0, INFINITE)
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if rc == WAIT_OBJECT_0:
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# Some input - read and print it
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flags, comstat = ClearCommError( self.handle )
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rc, data = ReadFile(self.handle, comstat.cbInQue, overlapped)
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WaitForSingleObject(overlapped.hEvent, INFINITE)
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sys.stdout.write(data)
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else:
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# Stop the thread!
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# Just incase the user input thread uis still going, close it
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sys.stdout.close()
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break
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def Run(self):
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self.eventStop = CreateEvent(None, 0, 0, None)
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# Start the reader and writer threads.
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user_thread = threading.Thread(target = self._UserInputReaderThread)
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user_thread.start()
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com_thread = threading.Thread(target = self._ComPortThread)
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com_thread.start()
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user_thread.join()
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com_thread.join()
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if __name__=='__main__':
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print("Serial port terminal demo - press Ctrl+C to exit")
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if len(sys.argv)<=1:
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port = FindModem()
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if port is None:
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print("No COM port specified, and no modem could be found")
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print("Please re-run this script with the name of a COM port (eg COM3)")
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sys.exit(1)
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else:
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port = sys.argv[1]
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tty = SerialTTY(port)
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tty.Run()
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