from functools import partial
from time import time
from typing import TYPE_CHECKING, cast
import qcodes.validators as vals
from qcodes.instrument import (
ChannelList,
InstrumentChannel,
VisaInstrument,
VisaInstrumentKWArgs,
)
if TYPE_CHECKING:
from typing_extensions import Unpack
from qcodes.parameters import Parameter
[docs]
class HarvardDecadacException(Exception):
pass
DACException = HarvardDecadacException
class DacReader:
@staticmethod
def _dac_parse(resp):
"""
Parses responses from the DAC. They should take the form of
"<cmd><resp>!" This command returns the value of resp.
"""
resp = resp.strip()
if resp[-1] != "!":
raise HarvardDecadacException(
f"Unexpected terminator on response: {resp}. Should end with '!'"
)
return resp.strip()[1:-1]
def _dac_v_to_code(self, volt):
"""
Convert a voltage to the internal dac code (number between 0-65536)
based on the minimum/maximum values of a given channel.
Midrange is 32768.
"""
if volt < self.min_val or volt > self.max_val:
raise ValueError(
f"Cannot convert voltage {volt} V to a voltage code, value out of range "
f"({self.min_val} V - {self.max_val} V)."
)
frac = (volt - self.min_val) / (self.max_val - self.min_val)
val = int(round(frac * 65535))
# extra check to be absolutely sure that the instrument does nothing
# receive an out-of-bounds value
if val > 65535 or val < 0:
raise ValueError(
f"Voltage ({volt} V) resulted in the voltage code {val}"
", which is not within the allowed range."
)
return val
def _dac_code_to_v(self, code):
"""
Convert a voltage to the internal dac code (number between 0-65536)
based on the minimum/maximum values of a given channel.
Midrange is 32768.
"""
frac = code / 65535.0
return (frac * (self.max_val - self.min_val)) + self.min_val
def _set_slot(self):
"""
Set the active DAC slot
"""
resp = self.ask_raw(f"B{self._slot};")
if int(self._dac_parse(resp)) != self._slot:
raise HarvardDecadacException(
"Unexpected return from DAC when setting slot: "
f"{resp}. DAC slot may not have been set."
)
def _set_channel(self):
"""
Set the active DAC channel
"""
resp = self.ask_raw(f"B{self._slot};C{self._channel};")
if resp.strip() != f"B{self._slot}!C{self._channel}!":
raise HarvardDecadacException(
f"Unexpected return from DAC when setting "
f"channel: {resp}. DAC channel may not have "
f"been set."
)
def _query_address(self, addr: int, count: int=1,
versa_eeprom: bool=False):
"""
Query the value at the dac address given.
Args:
addr (int): The address to query.
count (int): The number of bytes to query.
versa_eeprom(bool): do we want to read from the versadac
(slot) EEPROM
"""
# Check if we actually have anything to query
if count == 0:
return 0
# Validate address
addr = int(addr)
if addr < 0 or addr > 1107296266:
raise HarvardDecadacException(f"Invalid address {addr}.")
# Choose a poke command depending on whether we are querying a
# VERSADAC eeprom or main memory
# If we are writing to a VERSADAC, we must also set the slot.
if versa_eeprom:
self._set_slot()
query_command = "e;"
else:
query_command = "p;"
# Read a number of bytes from the device and convert to an int
val = 0
for i in range(count):
# Set DAC to point to address
ret = int(self._dac_parse(
self.ask_raw(f"A{addr};"))) # type: ignore[attr-defined]
if ret != addr:
raise HarvardDecadacException(f"Failed to set EEPROM address {addr}.")
val += int(self._dac_parse(self.ask_raw( # type: ignore[attr-defined]
query_command))) << (32*(count-i-1))
addr += 1
return val
def _write_address(self, addr: int, val: int,
versa_eeprom: bool=False) -> None:
"""
Write a value to a given DAC address
Args:
addr (int): The address to query.
val (int): The value to write.
versa_eeprom(bool): do we want to read
from the versadac (slot) EEPROM
"""
# Validate address
addr = int(addr)
if addr < 0 or addr > 1107296266:
raise HarvardDecadacException(f"Invalid address {addr}.")
# Validate value
val = int(val)
if val < 0 or val >= 2**32:
raise HarvardDecadacException(
f"Writing invalid value ({val}) to address {addr}."
)
# Choose a poke command depending on whether we are querying a
# VERSADAC eeprom or main memory. If we are writing to a versadac
# channel we must also set the slot
if versa_eeprom:
query_command = "e;"
write_command = "E"
self._set_slot()
else:
query_command = "p;"
write_command = "P"
# Write the value to the DAC
# Set DAC to point to address
ret = int(self._dac_parse(self.ask_raw(f"A{addr};"))) # type: ignore[attr-defined]
if ret != addr:
raise HarvardDecadacException(f"Failed to set EEPROM address {addr}.")
self.ask_raw(f"{write_command}{val};") # type: ignore[attr-defined]
# Check the write was successful
if (
int(self._dac_parse(self.ask_raw(query_command))) != val # type: ignore[attr-defined]
):
raise HarvardDecadacException(
f"Failed to write value ({val}) to address {addr}."
)
[docs]
class HarvardDecadacChannel(InstrumentChannel, DacReader):
"""
A single DAC channel of the DECADAC
"""
_CHANNEL_VAL = vals.Ints(0, 3)
def __init__(
self, parent: "HarvardDecadacSlot", name: str, channel, min_val=-5, max_val=5
):
super().__init__(parent, name)
# Validate slot and channel values
self._CHANNEL_VAL.validate(channel)
self._channel = channel
self._slot = self.parent._slot
# Calculate base address for querying channel parameters
# Note that the following values can be found using these offsets
# 0: Interrupt Period
# 4: DAC High Limit
# 5: DAC Low Limit
# 6: Slope (double)
# 8: DAC Value (double)
self._base_addr = 1536 + (16*4)*self._slot + 16*self._channel
# Store min/max voltages
assert(min_val < max_val)
self.min_val = min_val
self.max_val = max_val
# Add channel parameters
# Note we will use the older addresses to read the value from the dac
# rather than the newer 'd' command for backwards compatibility
self._volt_val = vals.Numbers(self.min_val, self.max_val)
self.volt: Parameter = self.add_parameter(
"volt",
get_cmd=partial(self._query_address, self._base_addr + 9, 1),
get_parser=self._dac_code_to_v,
set_cmd=self._set_dac,
set_parser=self._dac_v_to_code,
vals=self._volt_val,
label=f"channel {channel+self._slot*4}",
unit="V",
)
"""Parameter volt"""
# The limit commands are used to sweep dac voltages. They are not
# safety features.
self.lower_ramp_limit: Parameter = self.add_parameter(
"lower_ramp_limit",
get_cmd=partial(self._query_address, self._base_addr + 5),
get_parser=self._dac_code_to_v,
set_cmd="L{};",
set_parser=self._dac_v_to_code,
vals=self._volt_val,
label="Lower_Ramp_Limit",
unit="V",
)
"""Parameter lower_ramp_limit"""
self.upper_ramp_limit: Parameter = self.add_parameter(
"upper_ramp_limit",
get_cmd=partial(self._query_address, self._base_addr + 4),
get_parser=self._dac_code_to_v,
set_cmd="U{};",
set_parser=self._dac_v_to_code,
vals=self._volt_val,
label="Upper_Ramp_Limit",
unit="V",
)
"""Parameter upper_ramp_limit"""
self.update_period: Parameter = self.add_parameter(
"update_period",
get_cmd=partial(self._query_address, self._base_addr),
get_parser=int,
set_cmd="T{};",
set_parser=int,
vals=vals.Ints(50, 65535),
label="Update_Period",
unit="us",
)
"""Parameter update_period"""
self.slope: Parameter = self.add_parameter(
"slope",
get_cmd=partial(self._query_address, self._base_addr + 6, 2),
get_parser=int,
set_cmd="S{};",
set_parser=int,
vals=vals.Ints(-(2**32), 2**32),
label="Ramp_Slope",
)
"""Parameter slope"""
# Manual parameters to control whether DAC channels should ramp to
# voltages or jump
self._ramp_val = vals.Numbers(0, 10)
self.enable_ramp: Parameter = self.add_parameter(
"enable_ramp",
get_cmd=None,
set_cmd=None,
initial_value=False,
vals=vals.Bool(),
)
"""Parameter enable_ramp"""
self.ramp_rate: Parameter = self.add_parameter(
"ramp_rate",
get_cmd=None,
set_cmd=None,
initial_value=0.1,
vals=self._ramp_val,
unit="V/s",
)
"""Parameter ramp_rate"""
# Add ramp function to the list of functions
self.add_function("ramp", call_cmd=self._ramp, args=(self._volt_val,
self._ramp_val))
# If we have access to the VERSADAC (slot) EEPROM, we can set the
# initial value of the channel.
# NOTE: these values will be overwritten by a K3 calibration
if self.parent._VERSA_EEPROM_available:
_INITIAL_ADDR = [6, 8, 32774, 32776]
self.initial_value: Parameter = self.add_parameter(
"initial_value",
get_cmd=partial(
self._query_address, _INITIAL_ADDR[self._channel], versa_eeprom=True
),
get_parser=self._dac_code_to_v,
set_cmd=partial(
self._write_address, _INITIAL_ADDR[self._channel], versa_eeprom=True
),
set_parser=self._dac_v_to_code,
vals=vals.Numbers(self.min_val, self.max_val),
)
"""Parameter initial_value"""
def _ramp(self, val, rate, block=True):
"""
Ramp the DAC to a given voltage.
Params:
val (float): The voltage to ramp to in volts
rate (float): The ramp rate in units of volts/s
block (bool): Should the call block until the ramp is complete?
"""
# We need to know the current dac value (in raw units), as well as the
# update rate
c_volt = self.volt.get() # Current Voltage
if c_volt == val:
# If we are already at the right voltage, we don't need to ramp
return
c_val = self._dac_v_to_code(c_volt) # Current voltage in DAC units
e_val = self._dac_v_to_code(val) # Endpoint in DAC units
# Number of refreshes per second
t_rate = 1/(self.update_period.get() * 1e-6)
# Number of seconds to ramp
secs = abs((c_volt - val)/rate)
# The formula to calculate the slope is: Number of DAC steps divided by
# the number of time steps in the ramp multiplied by 65536
slope = int(((e_val - c_val)/(t_rate*secs))*65536)
# Now let's set up our limits and ramo slope
if slope > 0:
self.upper_ramp_limit.set(val)
else:
self.lower_ramp_limit.set(val)
self.slope.set(slope)
# Block until the ramp is complete is block is True
if block:
while self.slope.get() != 0:
pass
def _set_dac(self, code):
"""
Set the voltage on the dac channel, ramping if the enable_rate
parameter is set for this channel.
Params:
code (int): the DAC code to set the voltage to
"""
if self.enable_ramp.get():
self._ramp(self._dac_code_to_v(code), rate=self.ramp_rate.get())
else:
code = int(code)
self._set_channel()
self.ask_raw(f"U65535;L0;D{code};")
[docs]
def write(self, cmd):
"""
Overload write to set channel prior to any channel operations.
Since all commands are echoed back, we must keep track of responses
as well, otherwise commands receive the wrong response.
"""
self._set_channel()
return self.ask_raw(cmd)
[docs]
def ask(self, cmd):
"""
Overload ask to set channel prior to operations
"""
self._set_channel()
return self.ask_raw(cmd)
DacChannel = HarvardDecadacChannel
[docs]
class HarvardDecadacSlot(InstrumentChannel, DacReader):
"""
A single DAC Slot of the DECADAC
"""
_SLOT_VAL = vals.Ints(0, 4)
SLOT_MODE_DEFAULT = "Coarse"
def __init__(
self, parent: "HarvardDecadac", name: str, slot, min_val=-5, max_val=5
):
super().__init__(parent, name)
# Validate slot and channel values
self._SLOT_VAL.validate(slot)
self._slot = slot
# Store whether we have access to the VERSADAC EEPROM
self._VERSA_EEPROM_available = self.parent._VERSA_EEPROM_available
# Create a list of channels in the slot
channels = ChannelList(self, "Slot_Channels", parent.DAC_CHANNEL_CLASS)
for i in range(4):
channels.append(parent.DAC_CHANNEL_CLASS(self, f"Chan{i}",
i, min_val=min_val,
max_val=max_val))
self.add_submodule("channels", channels)
# Set the slot mode. Valid modes are:
# Off: Channel outputs are disconnected from the input, grounded
# with 10MOhm.
# Fine: 2-channel mode. Channels 0 and 1 are output, use 2 and 3
# for fine adjustment of Channels 0 and 1 respectively
# Coarse: All 4 channels are used as output
# FineCald: Calibrated 2-channel mode, with 0 and 1 output, 2 and 3
# used automatically for fine adjustment. This mode only works
# for calibrated DecaDAC's
#
# Unfortunately there is no known way of reading the slot mode hence
# this will be set in initialization
if self.parent._cal_supported:
slot_modes = {"Off": 0, "Fine": 1, "Coarse": 2, "FineCald": 3}
else:
slot_modes = {"Off": 0, "Fine": 1, "Coarse": 2}
self.slot_mode: Parameter = self.add_parameter(
"slot_mode",
get_cmd="m;",
get_parser=self._dac_parse,
set_cmd="M{};",
val_mapping=slot_modes,
)
"""Parameter slot_mode"""
# Enable all slots in coarse mode.
self.slot_mode.set(self.SLOT_MODE_DEFAULT)
[docs]
def write(self, cmd):
"""
Overload write to set channel prior to any channel operations.
Since all commands are echoed back, we must keep track of responses
as well, otherwise commands receive the wrong response.
"""
self._set_slot()
return self.ask_raw(cmd)
[docs]
def ask(self, cmd):
"""
Overload ask to set channel prior to operations
"""
self._set_slot()
return self.ask_raw(cmd)
DacSlot = HarvardDecadacSlot
[docs]
class HarvardDecadac(VisaInstrument, DacReader):
"""
The qcodes driver for the Decadac.
Tested with a Decadac firmware revion number 14081 (Decadac 139).
The message strategy is the following: always keep the queue empty, so
that self.visa_handle.ask(XXX) will return the answer to XXX and not
some previous event.
Attributes:
_ramp_state (bool): If True, ramp state is ON. Default False.
_ramp_time (int): The ramp time in ms. Default 100 ms.
"""
DAC_CHANNEL_CLASS = HarvardDecadacChannel
DAC_SLOT_CLASS = HarvardDecadacSlot
def __init__(
self,
name: str,
address: str,
min_val: float = -5,
max_val: float = 5,
**kwargs: "Unpack[VisaInstrumentKWArgs]",
) -> None:
"""
Creates an instance of the Decadac instruments
Args:
name: What this instrument is called locally.
address: The address of the DAC. For a serial port this
is ASRLn::INSTR where n is replaced with the address set in the
VISA control panel. Baud rate and other serial parameters must
also be set in the VISA control panel.
min_val: The minimum value in volts that can be output by the DAC.
This value should correspond to the DAC code 0.
max_val: The maximum value in volts that can be output by the DAC.
This value should correspond to the DAC code 65536.
**kwargs: kwargs are forwarded to base class.
"""
super().__init__(name, address, **kwargs)
# Do feature detection
self._feature_detect()
# Create channels
channels = ChannelList(self, "Channels", self.DAC_CHANNEL_CLASS,
snapshotable=False)
slots = ChannelList(self, "Slots", self.DAC_SLOT_CLASS)
for i in range(5): # Create the 6 DAC slots
slots.append(self.DAC_SLOT_CLASS(self, f"Slot{i}", i,
min_val, max_val))
slot_channels = slots[i].channels
slot_channels = cast(ChannelList, slot_channels)
channels.extend(slot_channels)
self.add_submodule("slots", slots.to_channel_tuple())
self.add_submodule("channels", channels.to_channel_tuple())
self.connect_message()
[docs]
def set_all(self, volt: float) -> None:
"""
Set all dac channels to a specific voltage. If channels are set to ramp
then the ramps will occur in sequence, not simultaneously.
Args:
volt(float): The voltage to set all gates to.
"""
for chan in self.channels:
chan.volt.set(volt)
[docs]
def ramp_all(self, volt, ramp_rate):
"""
Ramp all dac channels to a specific voltage at the given rate
simultaneously. Note that the ramps are not synchronized due to
communications time and DAC ramps starting as soon as the commands are
in.
Args:
volt(float): The voltage to ramp all channels to.
ramp_rate(float): The rate in volts per second to ramp
"""
# Start all channels ramping
for chan in self.channels:
chan._ramp(volt, ramp_rate, block=False)
# Wait for all channels to complete ramping.
# The slope is reset to 0 once ramping is complete.
for chan in self.channels:
while chan.slope.get():
pass
[docs]
def get_idn(self):
"""
Attempt to identify the dac. Since we don't have standard SCPI
commands, ``*IDN`` will do nothing on this DAC.
Returns:
A dict containing a serial and hardware version
"""
self._feature_detect()
return {"serial": self.serial_no, "hardware_version": self.version}
[docs]
def connect_message(self, idn_param='IDN', begin_time=None):
"""
Print a connect message, taking into account the lack of a standard
``*IDN`` on the Harvard DAC
Args:
idn_param: Unused
begin_time: time.time() when init started.
Default is self._t0, set at start of Instrument.__init__.
"""
# start with an empty dict, just in case an instrument doesn't
# heed our request to return all 4 fields.
t = time() - (begin_time or self._t0)
con_msg = (
"Connected to Harvard DecaDAC "
f"(hw ver: {self.version}, serial: {self.serial_no}) in {t:.2f}s"
)
print(con_msg)
[docs]
def __repr__(self):
"""Simplified repr giving just the class and name."""
return f"<{type(self).__name__}: {self.name}>"
def _feature_detect(self):
"""
Detect which features are available on the DAC by querying various
parameters.
"""
# Check whether EEPROM is installed
try:
if self._query_address(1107296256) == 21930:
self._EEPROM_available = True
else:
self._EEPROM_available = False
except HarvardDecadacException:
self._EEPROM_available = False
# Check whether we can set startup values for the DAC.
# This requires access to the EEPROM on each slot
# note from DV: the value never gets set to True in this driver.
# To avoid an error of a non existing attribute, here I set it to
# False by default
self._VERSA_EEPROM_available = False
try:
# Let's temporarily pretend to be slot 0
self._slot = 0
self._query_address(6, versa_eeprom=True)
del self._slot
except HarvardDecadacException:
pass
# Check whether calibration is supported
try:
if self._dac_parse(self.ask("k;")):
self._cal_supported = True
except HarvardDecadacException:
self._cal_supported = False
# Finally try and read the DAC version and S/N.
# This is only possible if the EEPROM is queryable.
if self._EEPROM_available:
self.version = self._query_address(1107296266)
self.serial_no = self._query_address(1107296264)
else:
self.version = 0
self.serial_no = 0
[docs]
def write(self, cmd):
"""
Since all commands are echoed back, we must keep track of responses
as well, otherwise commands receive the wrong response. Hence
all writes must also read a response.
"""
return self.ask(cmd)
Decadac = HarvardDecadac