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artiq/artiq/coredevice/sampler.py

148 lines
4.9 KiB
Python

from artiq.language.core import kernel, delay, portable
from artiq.language.units import ns
from artiq.coredevice import spi2 as spi
SPI_CONFIG = (0*spi.SPI_OFFLINE | 0*spi.SPI_END |
0*spi.SPI_INPUT | 0*spi.SPI_CS_POLARITY |
0*spi.SPI_CLK_POLARITY | 0*spi.SPI_CLK_PHASE |
0*spi.SPI_LSB_FIRST | 0*spi.SPI_HALF_DUPLEX)
SPI_CS_ADC = 0 # no CS, SPI_END does not matter, framing is done with CNV
SPI_CS_PGIA = 1 # separate SPI bus, CS used as RCLK
@portable
def adc_mu_to_volt(data, gain=0):
"""Convert ADC data in machine units to Volts.
:param data: 16 bit signed ADC word
:param gain: PGIA gain setting (0: 1, ..., 3: 1000)
:return: Voltage in Volts
"""
if gain == 0:
volt_per_lsb = 20./(1 << 16)
elif gain == 1:
volt_per_lsb = 2./(1 << 16)
elif gain == 2:
volt_per_lsb = .2/(1 << 16)
elif gain == 3:
volt_per_lsb = .02/(1 << 16)
else:
raise ValueError("invalid gain")
return data*volt_per_lsb
class Sampler:
"""Sampler ADC.
Controls the LTC2320-16 8 channel 16 bit ADC with SPI interface and
the switchable gain instrumentation amplifiers.
:param spi_adc_device: ADC SPI bus device name
:param spi_pgia_device: PGIA SPI bus device name
:param cnv_device: CNV RTIO TTLOut channel name
:param div: SPI clock divider (default: 8)
:param gains: Initial value for PGIA gains shift register
(default: 0x0000). Knowledge of this state is not transferred
between experiments.
:param core_device: Core device name
"""
kernel_invariants = {"bus_adc", "bus_pgia", "core", "cnv", "div"}
def __init__(self, dmgr, spi_adc_device, spi_pgia_device, cnv_device,
div=8, gains=0x0000, core_device="core"):
self.bus_adc = dmgr.get(spi_adc_device)
self.bus_adc.update_xfer_duration_mu(div, 32)
self.bus_pgia = dmgr.get(spi_pgia_device)
self.bus_pgia.update_xfer_duration_mu(div, 16)
self.core = dmgr.get(core_device)
self.cnv = dmgr.get(cnv_device)
self.div = div
self.gains = gains
@kernel
def init(self):
"""Initialize the device.
Sets up SPI channels.
"""
self.bus_adc.set_config_mu(SPI_CONFIG | spi.SPI_INPUT | spi.SPI_END,
32, self.div, SPI_CS_ADC)
self.bus_pgia.set_config_mu(SPI_CONFIG | spi.SPI_END,
16, self.div, SPI_CS_PGIA)
@kernel
def set_gain_mu(self, channel, gain):
"""Set instrumentation amplifier gain of a channel.
The four gain settings (0, 1, 2, 3) corresponds to gains of
(1, 10, 100, 1000) respectively.
:param channel: Channel index
:param gain: Gain setting
"""
gains = self.gains
gains &= ~(0b11 << (channel*2))
gains |= gain << (channel*2)
self.bus_pgia.write(gains << 16)
self.gains = gains
@kernel
def get_gains_mu(self):
"""Read the PGIA gain settings of all channels.
:return: The PGIA gain settings in machine units.
"""
self.bus_pgia.set_config_mu(SPI_CONFIG | spi.SPI_END | spi.SPI_INPUT,
16, self.div, SPI_CS_PGIA)
self.bus_pgia.write(self.gains << 16)
self.bus_pgia.set_config_mu(SPI_CONFIG | spi.SPI_END,
16, self.div, SPI_CS_PGIA)
self.gains = self.bus_pgia.read() & 0xffff
return self.gains
@kernel
def sample_mu(self, data):
"""Acquire a set of samples.
Perform a conversion and transfer the samples.
This assumes that the input FIFO of the ADC SPI RTIO channel is deep
enough to buffer the samples (half the length of `data` deep).
If it is not, there will be RTIO input overflows.
:param data: List of data samples to fill. Must have even length.
Samples are always read from the last channel (channel 7) down.
The `data` list will always be filled with the last item
holding to the sample from channel 7.
"""
self.cnv.pulse(30*ns) # t_CNVH
delay(450*ns) # t_CONV
mask = 1 << 15
for i in range(len(data)//2):
self.bus_adc.write(0)
for i in range(len(data) - 1, -1, -2):
val = self.bus_adc.read()
data[i] = val >> 16
val &= 0xffff
data[i - 1] = -(val & mask) + (val & ~mask)
@kernel
def sample(self, data):
"""Acquire a set of samples.
.. seealso:: :meth:`sample_mu`
:param data: List of floating point data samples to fill.
"""
n = len(data)
adc_data = [0]*n
self.sample_mu(adc_data)
for i in range(n):
channel = i + 8 - len(data)
gain = (self.gains >> (channel*2)) & 0b11
data[i] = adc_mu_to_volt(adc_data[i], gain)