Initial commit of open source Workload Automation.

wlauto/utils/serial_port.py

@@ -0,0 +1,111 @@
+#    Copyright 2013-2015 ARM Limited
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+
+import time
+from contextlib import contextmanager
+
+import serial
+import fdpexpect
+# Adding pexpect exceptions into this module's namespace
+from pexpect import EOF, TIMEOUT  # NOQA pylint: disable=W0611
+
+from wlauto.exceptions import HostError
+from wlauto.utils.log import LogWriter
+
+
+class PexpectLogger(LogWriter):
+
+    def __init__(self, kind):
+        """
+        File-like object class designed to be used for logging with pexpect or
+        fdpexect. Each complete line (terminated by new line character) gets logged
+        at DEBUG level. In complete lines are buffered until the next new line.
+
+        :param kind: This specified which of pexpect logfile attributes this logger
+                    will be set to. It should be "read" for logfile_read, "send" for
+                    logfile_send, and "" (emtpy string) for logfile.
+
+        """
+        if kind not in ('read', 'send', ''):
+            raise ValueError('kind must be "read", "send" or ""; got {}'.format(kind))
+        self.kind = kind
+        logger_name = 'serial_{}'.format(kind) if kind else 'serial'
+        super(PexpectLogger, self).__init__(logger_name)
+
+
+def pulse_dtr(conn, state=True, duration=0.1):
+    """Set the DTR line of the specified serial connection to the specified state
+    for the specified duration (note: the initial state of the line is *not* checked."""
+    conn.setDTR(state)
+    time.sleep(duration)
+    conn.setDTR(not state)
+
+
+@contextmanager
+def open_serial_connection(timeout, get_conn=False, init_dtr=None, *args, **kwargs):
+    """
+    Opens a serial connection to a device.
+
+    :param timeout: timeout for the fdpexpect spawn object.
+    :param conn: ``bool`` that specfies whether the underlying connection
+                 object should be yielded as well.
+    :param init_dtr: specifies the initial DTR state stat should be set.
+
+    All arguments are passed into the __init__ of serial.Serial. See
+    pyserial documentation for details:
+
+        http://pyserial.sourceforge.net/pyserial_api.html#serial.Serial
+
+    :returns: a pexpect spawn object connected to the device.
+              See: http://pexpect.sourceforge.net/pexpect.html
+
+    """
+    if init_dtr is not None:
+        kwargs['dsrdtr'] = True
+    try:
+        conn = serial.Serial(*args, **kwargs)
+    except serial.SerialException as e:
+        raise HostError(e.message)
+    if init_dtr is not None:
+        conn.setDTR(init_dtr)
+    conn.nonblocking()
+    conn.flushOutput()
+    target = fdpexpect.fdspawn(conn.fileno(), timeout=timeout)
+    target.logfile_read = PexpectLogger('read')
+    target.logfile_send = PexpectLogger('send')
+
+    # Monkey-patching sendline to introduce a short delay after
+    # chacters are sent to the serial. If two sendline s are issued
+    # one after another the second one might start putting characters
+    # into the serial device before the first one has finished, causing
+    # corruption. The delay prevents that.
+    tsln = target.sendline
+
+    def sendline(x):
+        tsln(x)
+        time.sleep(0.1)
+
+    target.sendline = sendline
+
+    if get_conn:
+        yield target, conn
+    else:
+        yield target
+
+    target.close()  # Closes the file descriptor used by the conn.
+    del conn
+
+