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lda: add docstring

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Yann Sionneau 2014-11-28 17:27:15 +01:00 committed by Sebastien Bourdeauducq
parent 44ec3eae3d
commit b9e7fdb80e
1 changed files with 53 additions and 0 deletions
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53
artiq/devices/lda/lda-controller.py
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@ -71,6 +71,19 @@ class HidError(Exception):
class Lda:
"""Lab Brick Digital Attenuator controller.
This controller depends on the hidapi library.
On Linux you should install hidapi-libusb shared library in a directory
listed in your LD_LIBRARY_PATH or in the conventional places (/usr/lib,
/lib, /usr/local/lib). This can be done either from hidapi sources
or by installing the libhidapi-libusb0 binary package on Debian-like OS.
On Windows you should put hidapi.dll shared library in the same directory
as the controller.
"""
_vendor_id = 0x041f
_product_ids = {
"LDA-102": 0x1207,
@ -78,6 +91,12 @@ class Lda:
}
def __init__(self, serial=None, product="LDA-102"):
"""
:param serial: The serial number.
:param product: The product identifier string: LDA-102, LDA-602 or sim.
"""
self.product = product
if serial is None and product != "sim":
serial = next(self.enumerate(product))
@ -105,12 +124,25 @@ class Lda:
return ret
def write(self, command, length, data=bytes()):
"""Writes a command to the Lab Brick device.
:param command: command ID.
:param length: number of meaningful bytes in the data array.
:param data: a byte array containing the payload of the command.
"""
# 0 is report id/padding
buf = struct.pack("BBB6s", 0, command, length, data)
res = self._check_error(hidapi.hid_write(self._dev, buf, len(buf)))
assert res == len(buf), res
def set(self, command, data):
"""Sends a SET command to the Lab Brick device.
:param command: command ID, must have most significant bit set.
:param data: payload of the command.
"""
assert command & 0x80
assert data
self.write(command, len(data), data)
@ -118,6 +150,15 @@ class Lda:
def get(self, command, length, timeout=1000):
# FIXME: this can collide with the status reports that the
# device sends out by itself
"""Sends a GET command to read back some value of the Lab Brick device.
:param int command: Command ID, most significant bit must be cleared.
:param int length: Length of the command, "count" in the datasheet.
:param int timeout: Timeout of the HID read in ms.
:return: Returns the value read from the device.
:rtype: bytes
"""
assert not command & 0x80
self.write(command, length)
buf = ctypes.create_string_buffer(8)
@ -130,12 +171,24 @@ class Lda:
return data
def get_attenuation(self):
"""Reads attenuation value from Lab Brick device.
:return: Returns the attenuation value in dB.
:rtype: float
"""
if self.product != "sim":
return ord(self.get(0x0d, 1))/4.
else:
return self._attenuation
def set_attenuation(self, attenuation):
"""Sets attenuation value of the Lab Brick device.
:param attenuation: Attenuation value in dB.
:type attenuation: int, float or Fraction
"""
if self.product != "sim":
self.set(0x8d, bytes(chr(int(round(attenuation*4))), 'ascii'))
else: