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      1 # Copyright (c) 2018 The Chromium OS Authors. All rights reserved.
      2 # Use of this source code is governed by a BSD-style license that can be
      3 # found in the LICENSE file.
      4 
      5 from autotest_lib.client.common_lib import error
      6 from autotest_lib.server.cros.network import telnet_helper
      7 
      8 
      9 class Attenuator(object):
     10     """Represents a minicircuits telnet-controlled 4-channel variable
     11     attenuator."""
     12 
     13     def __init__(self, host, num_atten=0):
     14         self._tnhelper = telnet_helper.TelnetHelper(
     15                 tx_cmd_separator="\r\n", rx_cmd_separator="\r\n", prompt="")
     16         self.host = host
     17         self.num_atten = num_atten
     18         self.open(host)
     19 
     20 
     21     def __del__(self):
     22         if self.is_open():
     23             self.close()
     24 
     25     def open(self, host, port=22):
     26         """Opens a telnet connection to the attenuator and queries basic
     27         information.
     28 
     29         @param host: Valid hostname
     30         @param port: Optional port number, defaults to 22
     31 
     32         """
     33         self._tnhelper.open(host, port)
     34 
     35         if self.num_atten == 0:
     36             self.num_atten = 1
     37 
     38         config_str = self._tnhelper.cmd("MN?")
     39 
     40         if config_str.startswith("MN="):
     41             config_str = config_str[len("MN="):]
     42 
     43         self.properties = dict(zip(['model', 'max_freq', 'max_atten'],
     44                                    config_str.split("-", 2)))
     45         self.max_atten = float(self.properties['max_atten'])
     46         self.min_atten = 0
     47 
     48     def is_open(self):
     49         """Returns true if telnet connection to attenuator is open."""
     50         return bool(self._tnhelper.is_open())
     51 
     52     def reopen(self, host, port=22):
     53         """Close and reopen telnet connection to the attenuator."""
     54         self._tnhelper.close()
     55         self._tnhelper.open(host, port)
     56 
     57     def close(self):
     58         """Closes the telnet connection."""
     59         self._tnhelper.close()
     60 
     61     def set_atten(self, channel, value):
     62         """Set attenuation of the attenuator for given channel (0-3).
     63 
     64         @param channel: Zero-based attenuator channel to set attenuation (0-3)
     65         @param value: Floating point value for attenuation to be set
     66         """
     67         if not self.is_open():
     68             raise error.TestError("Connection not open!")
     69 
     70         if channel >= self.num_atten:
     71             raise error.TestError("Attenuator channel out of range! Requested "
     72                                   "%d; max available %d" %
     73                                   (channel, self.num_atten))
     74 
     75         if not (self.min_atten <= value <= self.max_atten):
     76             raise error.TestError("Requested attenuator value %d not in range "
     77                                   "(%d - %d)" %
     78                                   (value, self.min_atten, self.max_atten))
     79         # The actual device uses one-based channel for channel numbers.
     80         if (int(self._tnhelper.cmd("CHAN:%d:SETATT:%d" %
     81                                   (channel + 1, value))) != 1):
     82             raise error.TestError("Error while setting attenuation on %d" %
     83                                   channel)
     84 
     85     def get_atten(self, channel):
     86         """Returns current attenuation of the attenuator for given channel.
     87 
     88         @param channel: Attenuator channel
     89         @returns the current attenuation value as a float
     90         """
     91         if not self.is_open():
     92             raise error.TestError("Connection not open!")
     93 
     94         if channel >= self.num_atten or channel < 0:
     95             raise error.TestError("Attenuator channel out of range! Requested "
     96                                   "%d; should be between 0 and max available "
     97                                   "%d" % (channel, self.num_atten))
     98 
     99         return float(self._tnhelper.cmd("CHAN:%d:ATT?" % (channel + 1)))
    100