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Usb device fixes #205

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Usb device fixes #205

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12922cb
For USB devices the physical address is sufficient for the only two U…
jayich Jul 16, 2015
77b14b2
We found that for two of our devices, a Rigol DG1022 and an Agilent D…
jayich Jul 16, 2015
094710d
labrad.util.wakeupCall already existed and looks more robust than ays…
jayich Jul 17, 2015
4d87cae
Deleted commented out old code.
jayich Jul 17, 2015
66b4835
Comment to clarify an obscure logic statements that handles the addre…
jayich Jul 17, 2015
f58ed8e
Included Exception.
jayich Jul 17, 2015
b397b5b
Including the "e" seems to be important.
jayich Jul 17, 2015
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51 changes: 40 additions & 11 deletions gpib_server.py
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Original file line number Diff line number Diff line change
Expand Up @@ -38,6 +38,7 @@

from labrad.server import LabradServer, setting
from twisted.internet.defer import inlineCallbacks
from twisted.internet import defer
from twisted.internet.reactor import callLater
from labrad.errors import DeviceNotSelectedError
import labrad.units as units
Expand Down Expand Up @@ -107,15 +108,10 @@ def refreshDevices(self):
deletions = set(self.devices.keys()) - set(addresses)
for addr in additions:
try:
if addr.startswith('GPIB'):
instName = addr
elif addr.startswith('TCPIP'):
instName = addr
elif addr.startswith('USB'):
instName = addr + '::INSTR'
else:
device_prefixes = ('GPIB', 'USB', 'TCPIP')
if not (addr.startswith(device_prefixes)):
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@maffoo maffoo Jul 17, 2015

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didn't know you could pass a tuple to startswith. nice.

continue
instr = rm.get_instrument(instName)
instr = rm.get_instrument(addr)
instr.write_termination = ''
instr.clear()
if addr.endswith('SOCKET'):
Expand Down Expand Up @@ -145,6 +141,23 @@ def getDevice(self, c):
instr = self.devices[c['addr']]
return instr

def asynchronous_wait(self, seconds, result=None):
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@maffoo maffoo Jul 17, 2015

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we have a utility function to do exactly this: labrad.util.wakeupCall

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@jayich jayich Jul 17, 2015

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@maffoo , yep, that works. Superior. See: 094710d

"""
Pause the reactor for seconds to wait for GPIB devices that require
time between read and write calls.

Parameters
----------
seconds: float, sleep time in seconds

Returns
-------
Deferred
"""
d = defer.Deferred()
callLater(seconds, d.callback, result)
return d

@setting(0, addr='s', returns='s')
def address(self, c, addr=None):
"""Get or set the GPIB address for this context.
Expand Down Expand Up @@ -176,10 +189,26 @@ def read(self, c, n_bytes=None):
Otherwise, reads until the device stops sending.
"""
instr = self.getDevice(c)
if n_bytes is None:
ans = instr.read_raw()
if instr.resource_name.startswith('USB'):
try:
if n_bytes is None:
ans = instr.read()
else:
ans = instr.read(n_bytes)
except:
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@maffoo maffoo Jul 17, 2015

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Seems dangerous to have a bare except here. Generally, I think it's preferable to do except Exception: so as not to catch things like KeyboardInterrupt

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@jayich jayich Jul 17, 2015

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Included Exception here: https://github.com/CampbellGroup/servers/commit/f58ed8e46092cfc9a768cd289c855817eef73550

self.asynchronous_wait(0.1)
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@maffoo maffoo Jul 17, 2015

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this would need a yield to actually wait for the deferred to fire before continuing:

yield self.asynchronous_wait(0.1)

or

yield labrad.util.wakeupCall(0.1)

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@jayich jayich Jul 17, 2015

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@maffoo, okay it appears that everything works without the yield. We tried with the yield and that ran into errors. The "read" method would likely need to use returnValue instead of return. I am not sure what else.

if n_bytes is None:
ans = instr.read()
else:
ans = instr.read(n_bytes)
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@maffoo maffoo Jul 17, 2015

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I'd rather not have this delay/retry logic here in the gpib server, since it seems like a device-specific requirement. Ideally, this would go in the device server for the devices that need it. One thing we might want to do is add a setting on the gpib server that just does a delay, so that then the device server could send a single packet that includes the required delays, e.g.:

p = cxn.gpib_bus.packet()
p.write(msg).delay(0.1).read()
result = yield p.send()
result.read

You could also do multiple writes with interleaved delays, etc, but all in one packet to the gpib bus server.

Similarly, we could add a delay parameter to the query setting, which would add a delay between the read and write in the same way.

ans = str(ans)
if ",," in ans:
ans = ans.replace(",,", ",") # rigol specific stupidity
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@maffoo maffoo Jul 17, 2015

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what's going on here?

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@jayich jayich Jul 17, 2015

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I added a clarifying comment in https://github.com/CampbellGroup/servers/commit/66b48359c2ac336a5ea292f17bec261f374338cc.

With this device connected we get the following with pyvisa 1.7.

>>> import visa
>>> rm = visa.ResourceManager()
>>> rigol = rm.get_instrument('USB0::0x09C4::0x0400::DG1D150900538::INSTR')
>>> rigol.write('*IDN?')
>>> rigol.read()
u'RIGOL TECHNOLOGIES,DG1022 ,DG1D150900538,,00.03.00.09.00.02.11\n'

The double commas, before 00.03 are the use case we are taking care of.

else:
ans = instr.read_raw(n_bytes)
if n_bytes is None:
ans = instr.read_raw()
else:
ans = instr.read_raw(n_bytes)
return str(ans).strip()

@setting(5, data='s', returns='s')
Expand Down