Serial port IO question

[David Stokes]

I am attempting to send a ^M (Control-M) down a serial port and then
read back from that same port.  The application is an old UPS that will
send back system status after a ^M.  The code below opens the port but
the readline seems to be returning what I wrote.  My guess is that I
haven't really grabbed I/O stream for the read operation.  Any
suggestions?

Dave Stokes
-------

#!/usr/bin/env python
import sys, string

upsdev = "/dev/ttyS1"   # Serial port attached to ups


class   get_ups:
    def __init__(self):
        print "Getting ups status"

    def get_ups_data_p(self):
        upsdata = open( upsdev, 'r+');      # open port to ups
        upsdata.write("\015")                   # send ^M to ask for
status
        upsdata.flush()
        upsbuffer = upsdata.readline()       # get status back
        upsdata.close()

if __name__ == '__main__':
    ups_status = get_ups()
    ups_status.get_ups_data_p()