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artiq/artiq/coredevice/sawg.py

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"""
Driver for the Smart Arbitrary Waveform Generator (SAWG) on RTIO.
The SAWG is an "improved DDS" built in gateware and interfacing to
high-speed DACs.
Output event replacement is supported except on the configuration channel.
"""
from artiq.language.types import TInt32, TFloat
from numpy import int32, int64
from artiq.language.core import kernel
from artiq.coredevice.spline import Spline
from artiq.coredevice.rtio import rtio_output
# sawg.Config addresses
_SAWG_DIV = 0
_SAWG_CLR = 1
_SAWG_IQ_EN = 2
# _SAWF_PAD = 3 # reserved
_SAWG_OUT_MIN = 4
_SAWG_OUT_MAX = 5
_SAWG_DUC_MIN = 6
_SAWG_DUC_MAX = 7
class Config:
"""SAWG configuration.
Exposes the configurable quantities of a single SAWG channel.
Access to the configuration registers for a SAWG channel can not
be concurrent. There must be at least :attr:`_rtio_interval` machine
units of delay between accesses. Replacement is not supported and will be
lead to an ``RTIOCollision`` as this is likely a programming error.
All methods therefore advance the timeline by the duration of one
configuration register transfer.
:param channel: RTIO channel number of the channel.
:param core: Core device.
"""
kernel_invariants = {"channel", "core", "_out_scale", "_duc_scale",
"_rtio_interval"}
def __init__(self, channel, core, cordic_gain=1.):
self.channel = channel
self.core = core
# normalized DAC output
self._out_scale = (1 << 15) - 1.
# normalized DAC output including DUC cordic gain
self._duc_scale = self._out_scale/cordic_gain
# configuration channel access interval
self._rtio_interval = int64(3*self.core.ref_multiplier)
@kernel
def set_div(self, div: TInt32, n: TInt32=0):
"""Set the spline evolution divider and current counter value.
The divider and the spline evolution are synchronized across all
spline channels within a SAWG channel. The DDS/DUC phase accumulators
always evolves at full speed.
.. note:: The spline evolution divider has not been tested extensively
and is currently considered a technological preview only.
:param div: Spline evolution divider, such that
``t_sawg_spline/t_rtio_coarse = div + 1``. Default: ``0``.
:param n: Current value of the counter. Default: ``0``.
"""
rtio_output((self.channel << 8) | _SAWG_DIV, div | (n << 16))
delay_mu(self._rtio_interval)
@kernel
def set_clr(self, clr0: TInt32, clr1: TInt32, clr2: TInt32):
"""Set the accumulator clear mode for the three phase accumulators.
When the ``clr`` bit for a given DDS/DUC phase accumulator is
set, that phase accumulator will be cleared with every phase offset
RTIO command and the output phase of the DDS/DUC will be
exactly the phase RTIO value ("absolute phase update mode").
.. math::
q^\prime(t) = p^\prime + (t - t^\prime) f^\prime
In turn, when the bit is cleared, the phase RTIO channels
determine a phase offset to the current (carrier-) value of the
DDS/DUC phase accumulator. This "relative phase update mode" is
sometimes also called “continuous phase mode”.
.. math::
q^\prime(t) = q(t^\prime) + (p^\prime - p) +
(t - t^\prime) f^\prime
Where:
* :math:`q`, :math:`q^\prime`: old/new phase accumulator
* :math:`p`, :math:`p^\prime`: old/new phase offset
* :math:`f^\prime`: new frequency
* :math:`t^\prime`: timestamp of setting new :math:`p`, :math:`f`
* :math:`t`: running time
:param clr0: Auto-clear phase accumulator of the ``phase0``/
``frequency0`` DUC. Default: ``True``
:param clr1: Auto-clear phase accumulator of the ``phase1``/
``frequency1`` DDS. Default: ``True``
:param clr2: Auto-clear phase accumulator of the ``phase2``/
``frequency2`` DDS. Default: ``True``
"""
rtio_output((self.channel << 8) | _SAWG_CLR, clr0 |
(clr1 << 1) | (clr2 << 2))
delay_mu(self._rtio_interval)
@kernel
def set_iq_en(self, i_enable: TInt32, q_enable: TInt32):
"""Enable I/Q data on this DAC channel.
Every pair of SAWG channels forms a buddy pair.
The ``iq_en`` configuration controls which DDS data is emitted to the
DACs.
Refer to the documentation of :class:`SAWG` for a mathematical
description of ``i_enable`` and ``q_enable``.
.. note:: Quadrature data from the buddy channel is currently
a technological preview only. The data is ignored in the SAWG
gateware and not added to the DAC output.
This is equivalent to the ``q_enable`` switch always being ``0``.
:param i_enable: Controls adding the in-phase
DUC-DDS data of *this* SAWG channel to *this* DAC channel.
Default: ``1``.
:param q_enable: controls adding the quadrature
DUC-DDS data of this SAWG's *buddy* channel to *this* DAC
channel. Default: ``0``.
"""
rtio_output((self.channel << 8) | _SAWG_IQ_EN, i_enable |
(q_enable << 1))
delay_mu(self._rtio_interval)
@kernel
def set_duc_max_mu(self, limit: TInt32):
"""Set the digital up-converter (DUC) I and Q data summing junctions
upper limit. In machine units.
The default limits are chosen to reach maximum and minimum DAC output
amplitude.
For a description of the limiter functions in normalized units see:
.. seealso:: :meth:`set_duc_max`
"""
rtio_output((self.channel << 8) | _SAWG_DUC_MAX, limit)
delay_mu(self._rtio_interval)
@kernel
def set_duc_min_mu(self, limit: TInt32):
""".. seealso:: :meth:`set_duc_max_mu`"""
rtio_output((self.channel << 8) | _SAWG_DUC_MIN, limit)
delay_mu(self._rtio_interval)
@kernel
def set_out_max_mu(self, limit: TInt32):
""".. seealso:: :meth:`set_duc_max_mu`"""
rtio_output((self.channel << 8) | _SAWG_OUT_MAX, limit)
delay_mu(self._rtio_interval)
@kernel
def set_out_min_mu(self, limit: TInt32):
""".. seealso:: :meth:`set_duc_max_mu`"""
rtio_output((self.channel << 8) | _SAWG_OUT_MIN, limit)
delay_mu(self._rtio_interval)
@kernel
def set_duc_max(self, limit: TFloat):
"""Set the digital up-converter (DUC) I and Q data summing junctions
upper limit.
Each of the three summing junctions has a saturating adder with
configurable upper and lower limits. The three summing junctions are:
* At the in-phase input to the ``phase0``/``frequency0`` fast DUC,
after the anti-aliasing FIR filter.
* At the quadrature input to the ``phase0``/``frequency0``
fast DUC, after the anti-aliasing FIR filter. The in-phase and
quadrature data paths both use the same limits.
* Before the DAC, where the following three data streams
are added together:
* the output of the ``offset`` spline,
* (optionally, depending on ``i_enable``) the in-phase output
of the ``phase0``/``frequency0`` fast DUC, and
* (optionally, depending on ``q_enable``) the quadrature
output of the ``phase0``/``frequency0`` fast DUC of the
buddy channel.
Refer to the documentation of :class:`SAWG` for a mathematical
description of the summing junctions.
:param limit: Limit value ``[-1, 1]``. The output of the limiter will
never exceed this limit. The default limits are the full range
``[-1, 1]``.
.. seealso::
* :meth:`set_duc_max`: Upper limit of the in-phase and quadrature
inputs to the DUC.
* :meth:`set_duc_min`: Lower limit of the in-phase and quadrature
inputs to the DUC.
* :meth:`set_out_max`: Upper limit of the DAC output.
* :meth:`set_out_min`: Lower limit of the DAC output.
"""
self.set_duc_max_mu(int32(round(limit*self._duc_scale)))
@kernel
def set_duc_min(self, limit: TFloat):
""".. seealso:: :meth:`set_duc_max`"""
self.set_duc_min_mu(int32(round(limit*self._duc_scale)))
@kernel
def set_out_max(self, limit: TFloat):
""".. seealso:: :meth:`set_duc_max`"""
self.set_out_max_mu(int32(round(limit*self._out_scale)))
@kernel
def set_out_min(self, limit: TFloat):
""".. seealso:: :meth:`set_duc_max`"""
self.set_out_min_mu(int32(round(limit*self._out_scale)))
class SAWG:
"""Smart arbitrary waveform generator channel.
The channel is parametrized as: ::
oscillators = exp(2j*pi*(frequency0*t + phase0))*(
amplitude1*exp(2j*pi*(frequency1*t + phase1)) +
amplitude2*exp(2j*pi*(frequency2*t + phase2)))
output = (offset +
i_enable*Re(oscillators) +
q_enable*Im(buddy_oscillators))
This parametrization can be viewed as two complex (quadrature) oscillators
(``frequency1``/``phase1`` and ``frequency2``/``phase2``) that are
executing and sampling at the coarse RTIO frequency. They can represent
frequencies within the first Nyquist zone from ``-f_rtio_coarse/2`` to
``f_rtio_coarse/2``.
.. note:: The coarse RTIO frequency ``f_rtio_coarse`` is the inverse of
``ref_period*multiplier``. Both are arguments of the ``Core`` device,
specified in the device database ``device_db.py``.
The sum of their outputs is then interpolated by a factor of
:attr:`parallelism` (2, 4, 8 depending on the bitstream) using a
finite-impulse-response (FIR) anti-aliasing filter (more accurately
a half-band filter).
The filter is followed by a configurable saturating limiter.
After the limiter, the data is shifted in frequency using a complex
digital up-converter (DUC, ``frequency0``/``phase0``) running at
:attr:`parallelism` times the coarse RTIO frequency. The first Nyquist
zone of the DUC extends from ``-f_rtio_coarse*parallelism/2`` to
``f_rtio_coarse*parallelism/2``. Other Nyquist zones are usable depending
on the interpolation/modulation options configured in the DAC.
The real/in-phase data after digital up-conversion can be offset using
another spline interpolator ``offset``.
The ``i_enable``/``q_enable`` switches enable emission of quadrature
signals for later analog quadrature mixing distinguishing upper and lower
sidebands and thus doubling the bandwidth. They can also be used to emit
four-tone signals.
.. note:: Quadrature data from the buddy channel is currently
ignored in the SAWG gateware and not added to the DAC output.
This is equivalent to the ``q_enable`` switch always being ``0``.
The configuration channel and the nine
:class:`artiq.coredevice.spline.Spline` interpolators are accessible as
attributes:
* :attr:`config`: :class:`Config`
* :attr:`offset`, :attr:`amplitude1`, :attr:`amplitude2`: in units
of full scale
* :attr:`phase0`, :attr:`phase1`, :attr:`phase2`: in units of turns
* :attr:`frequency0`, :attr:`frequency1`, :attr:`frequency2`: in units
of Hz
.. note:: The latencies (pipeline depths) of the nine data channels (i.e.
all except :attr:`config`) are matched. Equivalent channels (e.g.
:attr:`phase1` and :attr:`phase2`) are exactly matched. Channels of
different type or functionality (e.g. :attr:`offset` vs
:attr:`amplitude1`, DDS vs DUC, :attr:`phase0` vs :attr:`phase1`) are
only matched to within one coarse RTIO cycle.
:param channel_base: RTIO channel number of the first channel (amplitude).
The configuration channel and frequency/phase/amplitude channels are
then assumed to be successive channels.
:param parallelism: Number of output samples per coarse RTIO clock cycle.
:param core_device: Name of the core device that this SAWG is on.
"""
kernel_invariants = {"channel_base", "core", "parallelism",
"amplitude1", "frequency1", "phase1",
"amplitude2", "frequency2", "phase2",
"frequency0", "phase0", "offset"}
def __init__(self, dmgr, channel_base, parallelism, core_device="core"):
self.core = dmgr.get(core_device)
self.channel_base = channel_base
self.parallelism = parallelism
width = 16
time_width = 16
cordic_gain = 1.646760258057163 # Cordic(width=16, guard=None).gain
head_room = 1.001
self.config = Config(channel_base, self.core, cordic_gain)
self.offset = Spline(width, time_width, channel_base + 1,
self.core, 2.*head_room)
self.amplitude1 = Spline(width, time_width, channel_base + 2,
self.core, 2*head_room*cordic_gain**2)
self.frequency1 = Spline(3*width, time_width, channel_base + 3,
self.core, 1/self.core.coarse_ref_period)
self.phase1 = Spline(width, time_width, channel_base + 4,
self.core, 1.)
self.amplitude2 = Spline(width, time_width, channel_base + 5,
self.core, 2*head_room*cordic_gain**2)
self.frequency2 = Spline(3*width, time_width, channel_base + 6,
self.core, 1/self.core.coarse_ref_period)
self.phase2 = Spline(width, time_width, channel_base + 7,
self.core, 1.)
self.frequency0 = Spline(2*width, time_width, channel_base + 8,
self.core,
parallelism/self.core.coarse_ref_period)
self.phase0 = Spline(width, time_width, channel_base + 9,
self.core, 1.)
@kernel
def reset(self):
"""Re-establish initial conditions.
This clears all spline interpolators, accumulators and configuration
settings.
This method advances the timeline by the time required to perform all
7 writes to the configuration channel, plus 9 coarse RTIO cycles.
"""
self.config.set_div(0, 0)
self.config.set_clr(1, 1, 1)
self.config.set_iq_en(1, 0)
self.config.set_duc_min(-1.)
self.config.set_duc_max(1.)
self.config.set_out_min(-1.)
self.config.set_out_max(1.)
self.frequency0.set_mu(0)
coarse_cycle = int64(self.core.ref_multiplier)
delay_mu(coarse_cycle)
self.frequency1.set_mu(0)
delay_mu(coarse_cycle)
self.frequency2.set_mu(0)
delay_mu(coarse_cycle)
self.phase0.set_mu(0)
delay_mu(coarse_cycle)
self.phase1.set_mu(0)
delay_mu(coarse_cycle)
self.phase2.set_mu(0)
delay_mu(coarse_cycle)
self.amplitude1.set_mu(0)
delay_mu(coarse_cycle)
self.amplitude2.set_mu(0)
delay_mu(coarse_cycle)
self.offset.set_mu(0)
delay_mu(coarse_cycle)
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