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