# coding: utf-8
import time
from time import sleep, time
from re import fullmatch, findall
from typing import Union, Optional, List, Iterable
import logging
from warnings import warn
from .meta_inout import InOut
from .._global import OptionalModule
try:
import RPi.GPIO as GPIO
except (ModuleNotFoundError, ImportError):
GPIO = OptionalModule("RPi.GPIO")
try:
import spidev
except (ModuleNotFoundError, ImportError):
spidev = OptionalModule("spidev")
# ADS1256 gain channel
Ads1256_gain = {1: 0b000,
2: 0b001,
4: 0b010,
8: 0b011,
16: 0b100,
32: 0b101,
64: 0b110}
# ADS1256 data rate
Ads1256_drate = {2.5: 0x03,
5: 0x13,
10: 0x20,
15: 0x33,
25: 0x43,
30: 0x53,
50: 0x63,
60: 0x72,
100: 0x82,
500: 0x92,
1000: 0xA1,
2000: 0xB0,
3750: 0xC0,
7500: 0xD0,
15000: 0xE0,
30000: 0xF0}
# Ads1256 registration definition
Ads1256_reg = {'REG_STATUS': 0,
'REG_MUX': 1,
'REG_ADCON': 2,
'REG_DRATE': 3,
'REG_IO': 4,
'REG_OFC0': 5,
'REG_OFC1': 6,
'REG_OFC2': 7,
'REG_FSC0': 8,
'REG_FSC1': 9,
'REG_FSC2': 10}
# Ads1256 command definition
Ads1256_cmd = {'CMD_WAKEUP': 0x00,
'CMD_RDATA': 0x01,
'CMD_RDATAC': 0x03,
'CMD_SDATAC': 0x0F,
'CMD_RREG': 0x10,
'CMD_WREG': 0x50,
'CMD_SELFCAL': 0xF0,
'CMD_SELFOCAL': 0xF1,
'CMD_SELFGCAL': 0xF2,
'CMD_SYSOCAL': 0xF3,
'CMD_SYSGCAL': 0xF4,
'CMD_SYNC': 0xFC,
'CMD_STANDBY': 0xFD,
'CMD_RESET': 0xFE}
# Dac8532 channels definition
Dac8532_chan = {0: 0x10,
1: 0x24}
# Waveshare AD/DA pins definition
AD_DA_pins = {'RST_PIN_ADS': 18,
'CS_PIN_ADS': 22,
'DRDY_PIN_ADS': 17,
'CS_PIN_DAC': 23}
[docs]
class WaveshareADDA(InOut):
"""Class for controlling Waveshare's AD/DA Raspberry Pi hat.
It communicates over the SPI protocol and the GPIOs. It allows to
read values from the 8-channels ADC and/or to set the 2-channels DAC. The hat
can acquire up to 30000 samples per second, although this data rate is
impossible to achieve using Crappy.
Important:
This class is specifically meant to be used on a Raspberry Pi.
.. versionadded:: 1.4.0
.. versionchanged:: 2.0.0 renamed from *Waveshare_ad_da* to *WaveshareADDA*
"""
[docs]
def __init__(self,
dac_channels: Optional[Iterable[str]] = None,
adc_channels: Optional[Iterable[str]] = None,
gain_hardware: int = 1,
v_ref: float = 3.3,
gain: float = 1,
offset: float = 0,
sample_rate: Union[int, float] = 100) -> None:
"""Checks the validity of the arguments.
Args:
dac_channels: An iterable (like a :obj:`list` or a :obj:`tuple`) of
:obj:`str` representing the channels to be set. The syntax for each
string is 'DACi' with i being either `0` or `1`.
adc_channels: An iterable (like a :obj:`list` or a :obj:`tuple`) of
:obj:`str` representing the channels to read. The syntax for all the
strings is either:
::
'ADi' (i in range(8))
or else:
::
'ADi - ADj' (i, j in range(8))
gain_hardware: The gain to be used by the programmable gain amplifier.
Setting a high gain allows to read small voltages with a better
precision, but it might saturate the sensor for higher voltages. The
available gain values are:
::
1, 2, 4, 8, 16, 32, 64
v_ref: The voltage reference set by the `VREF` jumper. When reading
single inputs, ``v_ref`` is the value the ADC compares the signals
with. In a similar way, the maximum output voltage of the DAC is
``v_ref``. `3.3` and `5` are the only possible values for this setting,
as the Raspberry Pi can only provide `3.3V` and `5V`.
gain: Allows to tune the output values of the ADC according to the
formula : :math:`output = gain * tension + offset`. The same gain
applies to all the outputs.
offset: Allows to tune the output values of the ADC according to the
formula : :math:`output = gain * tension + offset`. The same offset
applies to all the outputs.
sample_rate: The ADC data output rate in SPS. The available values are:
::
2.5, 5, 10, 15, 25, 30, 50, 60, 100, 500,
1000, 2000, 3750, 7500, 15000, 30000
Warning:
- ``adc_channels``:
For reading single inputs the `JMP_AGND` jumper should normally be
connected, whereas it should be disconnected for reading differential
inputs. It is however possible to set a different reference than `AGND`
for single input measurements, in which case the `JMP_AGND` jumper
should not be connected and the voltage reference should be plugged
in the `AINCOM` pin.
The AD/DA offers the possibility to read single inputs or differential
inputs, but not both at the same time ! This is due to the `JMP_AGND`
jumper. For measuring both input types simultaneously, is it necessary
to connect `AGND` to one of the channels (for example `AD0`). Then all
single inputs `'ADi'` should be replaced by `'ADi - AD0'`. They are
then considered as differential inputs.
The ADC channels voltages should not be lower than `AGND-0.1V`, and not
be greater than `AGND+5.1V`. This is independent of `VREF` value.
Note:
- ``adc_channels``:
If multiple channels to read are given, they are read in a sequential
way. This means that there's a small delay between each acquisition,
and the timeframe is thus less accurate for the last channels than
for the first ones. If time precision matters it is preferable to
read as few channels as possible !
- ``vref``:
`VREF` can be set independently of the chosen `VCC` value. The `VCC`
value has no influence on the ADC behaviour as it is always powered
up with `5V`. Same goes for the DAC.
"""
warn(f"Starting from version 2.1.0, {type(self).__name__} will be moved "
f"to crappy.collection. Your code that uses it will still work as "
f"is, except you will now need to import crappy.collection at the "
f"top of your script.", FutureWarning)
self._bus = None
super().__init__()
if gain_hardware not in Ads1256_gain:
raise ValueError("gain_hardware should be in {}".format(list(
Ads1256_gain.keys())))
else:
self._gain_hardware = gain_hardware
if sample_rate not in Ads1256_drate:
raise ValueError("sample_rate should be in {}".format(list(
Ads1256_drate.keys())))
else:
self._sample_rate = sample_rate
if v_ref not in [3.3, 5]:
raise ValueError("v_ref should be either 3.3 or 5")
else:
self._v_ref = v_ref
self._channel_set = False
if dac_channels is None and adc_channels is None:
self.log(logging.WARNING, "The AD/DA doesn't read nor write anything")
self._channels_write = []
if dac_channels is not None:
for chan in dac_channels:
# Checking if the format matches
if fullmatch(r'DAC[0-1]', chan) is None:
raise ValueError("Valid format for dac_channels values is 'DACi' "
"with i either 0 or 1")
else:
self._channels_write.append(int(findall(r'\d', chan)[0]))
self.log(logging.DEBUG, f"Channels to write to: {self._channels_write}")
self._channels_read = []
if adc_channels is not None:
for chan in adc_channels:
# Checking if the format matches
if fullmatch(r'AD[0-7]', chan) is None and \
fullmatch(r'AD[0-7]\s?-\s?AD[0-7]', chan) is None:
raise ValueError("Valid formats for adc_channels values are "
"either 'ADi' (i in range(8)) or 'ADi - ADj'")
else:
# Extracting the channel numbers
chan = [int(i) for i in findall(r'\d', chan)]
# If only one channel provided, it has to be compared to GND
if len(chan) == 1:
chan.append(8)
# Making sure the two channels are not identical
if chan[0] == chan[1]:
raise ValueError("The two channels are the same !")
self._channels_read.append(chan)
self.log(logging.DEBUG, f"Channels to read from: {self._channels_read}")
self._gain = gain
self._offset = offset
self.log(logging.INFO, "Opening the SPI communication with the AD/DA")
self._bus = spidev.SpiDev(0, 0)
[docs]
def open(self) -> None:
"""Sets the SPI communication, the GPIOs and the device."""
# Setting the GPIOs for communicating with the AD/DA
self.log(logging.INFO, "Setting up the GPIOs")
GPIO.setmode(GPIO.BCM)
GPIO.setup(AD_DA_pins['RST_PIN_ADS'], GPIO.OUT)
GPIO.setup(AD_DA_pins['CS_PIN_ADS'], GPIO.OUT)
GPIO.setup(AD_DA_pins['DRDY_PIN_ADS'], GPIO.IN,
pull_up_down=GPIO.PUD_UP)
GPIO.setup(AD_DA_pins['CS_PIN_DAC'], GPIO.OUT)
# Setting the SPI
self.log(logging.INFO, "Setting up the SPI connection")
self._bus.max_speed_hz = 40000
self._bus.mode = 1
self._bus.no_cs = True
self._reset()
# Setting the ADS according to the user parameters
buf = [Ads1256_gain[self._gain_hardware], Ads1256_drate[self._sample_rate]]
GPIO.output(AD_DA_pins['CS_PIN_ADS'], GPIO.LOW)
cmd = [Ads1256_cmd['CMD_WREG'] | Ads1256_reg['REG_ADCON'], 0x01] + buf
self.log(logging.DEBUG, f"Writing {cmd} to the SPI bus")
self._bus.writebytes(cmd)
GPIO.output(AD_DA_pins['CS_PIN_ADS'], GPIO.HIGH)
sleep(0.001)
[docs]
def get_data(self) -> List[float]:
"""Reads data from all the user-specified ADC channels, in a sequential
way.
Data is returned in Volts, but this can be tuned using gain and offset.
Returns:
A :obj:`list` containing the timestamp, and then the values for each
channel to read.
"""
out = [time()]
# The values are read one channel after the other, not simultaneously
for chan in self._channels_read:
GPIO.output(AD_DA_pins['CS_PIN_ADS'], GPIO.LOW)
# Switching channel only if necessary, except for the first loop
if len(self._channels_read) > 1 or not self._channel_set:
cmd = [Ads1256_cmd['CMD_WREG'] | Ads1256_reg['REG_MUX'], 0x00,
(chan[0] << 4) | chan[1]]
self.log(logging.DEBUG, f"Writing {cmd} to the SPI bus")
self._bus.writebytes(cmd)
# The ADS has to be synchronized again when switching channel
self.log(logging.DEBUG, f"Writing {[Ads1256_cmd['CMD_SYNC']]} to the "
f"SPI bus")
self._bus.writebytes([Ads1256_cmd['CMD_SYNC']])
self.log(logging.DEBUG, f"Writing {[Ads1256_cmd['CMD_WAKEUP']]} to "
f"the SPI bus")
self._bus.writebytes([Ads1256_cmd['CMD_WAKEUP']])
self._channel_set = True
# Reading the output value
self._wait_drdy()
self.log(logging.DEBUG, f"Writing {[Ads1256_cmd['CMD_RDATA']]} to the "
f"SPI bus")
self._bus.writebytes([Ads1256_cmd['CMD_RDATA']])
buf = self._bus.readbytes(3)
self.log(logging.DEBUG, f"Read {buf} from the SPI bus")
GPIO.output(AD_DA_pins['CS_PIN_ADS'], GPIO.HIGH)
# Converting the raw output into Volts
out_raw = (buf[0] << 16) | (buf[1] << 8) | buf[2]
if out_raw & 0x800000:
out_raw -= 2 ** 24
value = self._v_ref / self._gain_hardware * out_raw / 2 ** 23
out.append(self._offset + self._gain * value)
return out
[docs]
def set_cmd(self, *cmd: float) -> None:
"""Sets the user-specified DAC channels according to the input values.
Args:
cmd: The input values as :obj:`float`, in Volts.
"""
# The values are set one channel after the other, not simultaneously
for val, channel in zip(cmd, self._channels_write):
if not 0 <= val <= self._v_ref:
raise ValueError("Desired output voltage should be between 0 and "
"v_ref")
digit = int((2 ** 16 - 1) * val / self._v_ref)
GPIO.output(AD_DA_pins['CS_PIN_DAC'], GPIO.LOW)
cmd = [Dac8532_chan[channel], digit >> 8, digit & 0xFF]
self.log(logging.DEBUG, f"Writing {cmd} to the SPI bus")
self._bus.writebytes(cmd)
GPIO.output(AD_DA_pins['CS_PIN_DAC'], GPIO.HIGH)
[docs]
def close(self) -> None:
"""Releases the GPIOs."""
if self._bus is not None:
self.log(logging.INFO, "Closing the SPI communication with the AD/DA")
self._bus.close()
self.log(logging.INFO, "Cleaning up the GPIOs")
GPIO.cleanup()
@staticmethod
def _reset() -> None:
"""Resets the ADC."""
GPIO.output(AD_DA_pins['RST_PIN_ADS'], GPIO.HIGH)
sleep(0.2)
GPIO.output(AD_DA_pins['RST_PIN_ADS'], GPIO.LOW)
sleep(0.2)
GPIO.output(AD_DA_pins['RST_PIN_ADS'], GPIO.HIGH)
@staticmethod
def _wait_drdy() -> None:
"""Waits until the `DRDY` pin is driven low, meaning that an ADC conversion
is ready."""
t0 = time()
while GPIO.input(AD_DA_pins['DRDY_PIN_ADS']):
if time() - t0 > 1:
raise TimeoutError("Couldn't get conversion result from the ADC")