Fix visa readbytes (#192)

* Replace deprecated ask method for query in visa session.

* Update gitignore and add test requirements

* Replace visa read with with read_bytes

* Add encode parameter to instrument.read()

- Introduce unpacking of IEEE-754/64 double real numbers.

* Add newest pyvisa package to requirements.txt

- Removed extras_require from setup.py

* Update read mock call with utf-8

* Replace exception NotImplemented with NotImplementedError

* Change read method signature on pm100usb

* Revert change to _extras_require_

* Add pyvisa 1.9.x install requirement

* Fix pyvisa requirement

* Replace NotImplementedError with ValueError on abstract_comm

* Loosen pyvisa versioning requirements

* Use codecs module to determine valid builtin encode types

.gitignore

@@ -10,6 +10,10 @@ Thumbs.db
 ## Build directories ##
 doc/_build
 
+## Venv
+.venv/
+
+
 ## setup.py generated files ##
 MANIFEST
 
@@ -20,6 +24,7 @@ MANIFEST
 *.so
 
 # Packages
+.egg/
 *.egg
 *.egg-info
 dist

instruments/abstract_instruments/comm/abstract_comm.py

@@ -11,7 +11,9 @@
 from __future__ import unicode_literals
 
 import abc
+import codecs
 import logging
+import struct
 
 from future.utils import with_metaclass
 
@@ -202,7 +204,14 @@ def read(self, size=-1, encoding="utf-8"):
         :return: The read string from the connection
         :rtype: `str`
         """
-        return self.read_raw(size).decode(encoding)
+        try:
+            codecs.lookup(encoding)
+            return self.read_raw(size).decode(encoding)
+        except LookupError:
+            if encoding == 'IEEE-754/64':
+                return struct.unpack('>d', self.read_raw(size))[0]
+            else:
+                raise ValueError("Encoding {} is not currently supported.".format(encoding))
 
     def sendcmd(self, msg):
         """

instruments/abstract_instruments/comm/visa_communicator.py

@@ -124,14 +124,11 @@ def read_raw(self, size=-1):
         :rtype: `bytes`
         """
         if size >= 0:
-            while len(self._buf) < size:
-                data = self._conn.read()
-                if data == "":
-                    break
-                self._buf += data
+            self._buf += self._conn.read_bytes(size)
             msg = self._buf[:size]
             # Remove the front of the buffer.
             del self._buf[:size]
+
         elif size == -1:
             # Read the whole contents, appending the buffer we've already read.
             msg = self._buf + self._conn.read()
@@ -193,4 +190,4 @@ def _query(self, msg, size=-1):
         :rtype: `str`
         """
         msg += self._terminator
-        return self._conn.ask(msg)
+        return self._conn.query(msg)

instruments/abstract_instruments/instrument.py

@@ -151,7 +151,7 @@ def query(self, cmd, size=-1):
                 )
         return value
 
-    def read(self, size=-1):
+    def read(self, size=-1, encoding="utf-8"):
         """
         Read the last line.
 
@@ -161,7 +161,7 @@ def read(self, size=-1):
             connected instrument.
         :rtype: `str`
         """
-        return self._file.read(size)
+        return self._file.read(size, encoding)
 
     # PROPERTIES #
 

instruments/tests/test_base_instrument.py

@@ -710,13 +710,13 @@ def test_instrument_read():
     inst._file.read.return_value = "foobar"
 
     assert inst.read() == "foobar"
-    inst._file.read.assert_called_with(-1)
+    inst._file.read.assert_called_with(-1, 'utf-8')
 
     inst._file = mock.MagicMock()
     inst._file.read.return_value = "foobar"
 
     assert inst.read(6) == "foobar"
-    inst._file.read.assert_called_with(6)
+    inst._file.read.assert_called_with(6, 'utf-8')
 
 
 def test_instrument_write():

instruments/thorlabs/pm100usb.py

@@ -222,7 +222,7 @@ def averaging_count(self, newval):
 
     })
 
-    def read(self, size=-1):
+    def read(self, size=-1, encoding='utf-8'):
         """
         Reads a measurement from this instrument, according to its current
         configuration mode.

requirements.txt

@@ -1,5 +1,6 @@
 numpy
 pyserial
+pyvisa>=1.9
 quantities>=0.12.1
 future>=0.15
 enum34

setup.py

@@ -37,6 +37,7 @@
 INSTALL_REQUIRES = [
     "numpy",
     "pyserial>=3.3",
+    "pyvisa>=1.9",
     "quantities",
     "enum34",
     "future",
@@ -45,9 +46,7 @@
     "pyusb",
     "ruamel.yaml"
 ]
-EXTRAS_REQUIRE = {
-    'VISA': ["pyvisa"]
-}
+
 
 # HELPER FUNCTONS ############################################################
 
@@ -62,6 +61,7 @@ def read(*parts):
     with codecs.open(os.path.join(HERE, *parts), "rb", "utf-8") as f:
         return f.read()
 
+
 META_FILE = read(META_PATH)
 
 
@@ -77,18 +77,22 @@ def find_meta(meta):
         return meta_match.group(1)
     raise RuntimeError("Unable to find __{meta}__ string.".format(meta=meta))
 
+
 # MAIN #######################################################################
 
-if __name__ == "__main__":
-    setup(
-        name=find_meta("title"),
-        version=find_meta("version"),
-        url=find_meta("uri"),
-        author=find_meta("author"),
-        author_email=find_meta("email"),
-        packages=PACKAGES,
-        install_requires=INSTALL_REQUIRES,
-        extras_require=EXTRAS_REQUIRE,
-        description=find_meta("description"),
-        classifiers=CLASSIFIERS
-    )
+
+setup(
+    name=find_meta("title"),
+    version=find_meta("version"),
+    url=find_meta("uri"),
+    author=find_meta("author"),
+    author_email=find_meta("email"),
+    packages=PACKAGES,
+    install_requires=INSTALL_REQUIRES,
+    tests_require=[
+        'pytest >= 2.9.1',
+        'hypothesis'
+    ],
+    description=find_meta("description"),
+    classifiers=CLASSIFIERS
+)