from __future__ import (
unicode_literals,
print_function,
absolute_import,
division,
)
str = type('')
from .exc import DeviceClosed, InputDeviceError
from .devices import Device
from .spi import SPI
[docs]class SPIDevice(Device):
"""
Extends :class:`Device`. Represents a device that communicates via the SPI
protocol.
See :ref:`spi_args` for information on the keyword arguments that can be
specified with the constructor.
"""
def __init__(self, **spi_args):
self._spi = SPI(**spi_args)
[docs] def close(self):
if self._spi:
s = self._spi
self._spi = None
s.close()
super(SPIDevice, self).close()
@property
def closed(self):
return self._spi is None
def __repr__(self):
try:
self._check_open()
return "<gpiozero.%s object using %r>" % (self.__class__.__name__, self._spi)
except DeviceClosed:
return "<gpiozero.%s object closed>" % self.__class__.__name__
class MCP3xxx(AnalogInputDevice):
"""
Extends :class:`AnalogInputDevice` to implement an interface for all ADC
chips with a protocol similar to the Microchip MCP3xxx series of devices.
"""
def __init__(self, channel=0, bits=10, differential=False, **spi_args):
self._channel = channel
self._bits = bits
self._differential = bool(differential)
super(MCP3xxx, self).__init__(bits, **spi_args)
@property
def channel(self):
"""
The channel to read data from. The MCP3008/3208/3304 have 8 channels
(0-7), while the MCP3004/3204/3302 have 4 channels (0-3), and the
MCP3301 only has 1 channel.
"""
return self._channel
@property
def differential(self):
"""
If ``True``, the device is operated in pseudo-differential mode. In
this mode one channel (specified by the channel attribute) is read
relative to the value of a second channel (implied by the chip's
design).
Please refer to the device data-sheet to determine which channel is
used as the relative base value (for example, when using an
:class:`MCP3008` in differential mode, channel 0 is read relative to
channel 1).
"""
return self._differential
def _read(self):
# MCP3008/04 or MCP3208/04 protocol looks like the following:
#
# Byte 0 1 2
# ==== ======== ======== ========
# Tx 0001MCCC xxxxxxxx xxxxxxxx
# Rx xxxxxxxx x0RRRRRR RRRRxxxx for the 3004/08
# Rx xxxxxxxx x0RRRRRR RRRRRRxx for the 3204/08
#
# The transmit bits start with 3 preamble bits "000" (to warm up), a
# start bit "1" followed by the single/differential bit (M) which is 1
# for single-ended read, and 0 for differential read, followed by
# 3-bits for the channel (C). The remainder of the transmission are
# "don't care" bits (x).
#
# The first byte received and the top 1 bit of the second byte are
# don't care bits (x). These are followed by a null bit (0), and then
# the result bits (R). 10 bits for the MCP300x, 12 bits for the
# MCP320x.
#
# XXX Differential mode still requires testing
data = self._spi.transfer([16 + [8, 0][self.differential] + self.channel, 0, 0])
return ((data[1] & 63) << (self.bits - 6)) | (data[2] >> (14 - self.bits))
class MCP33xx(MCP3xxx):
"""
Extends :class:`MCP3xxx` with functionality specific to the MCP33xx family
of ADCs; specifically this handles the full differential capability of
these chips supporting the full 13-bit signed range of output values.
"""
def __init__(self, channel=0, differential=False, **spi_args):
super(MCP33xx, self).__init__(channel, 12, differential, **spi_args)
def _read(self):
# MCP3304/02 protocol looks like the following:
#
# Byte 0 1 2
# ==== ======== ======== ========
# Tx 0001MCCC xxxxxxxx xxxxxxxx
# Rx xxxxxxxx x0SRRRRR RRRRRRRx
#
# The transmit bits start with 3 preamble bits "000" (to warm up), a
# start bit "1" followed by the single/differential bit (M) which is 1
# for single-ended read, and 0 for differential read, followed by
# 3-bits for the channel (C). The remainder of the transmission are
# "don't care" bits (x).
#
# The first byte received and the top 1 bit of the second byte are
# don't care bits (x). These are followed by a null bit (0), then the
# sign bit (S), and then the 12 result bits (R).
#
# In single read mode (the default) the sign bit is always zero and the
# result is effectively 12-bits. In differential mode, the sign bit is
# significant and the result is a two's-complement 13-bit value.
#
# The MCP3301 variant of the chip always operates in differential
# mode and effectively only has one channel (composed of an IN+ and
# IN-). As such it requires no input, just output. This is the reason
# we split out _send() below; so that MCP3301 can override it.
data = self._spi.transfer(self._send())
# Extract the last two bytes (again, for MCP3301)
data = data[-2:]
result = ((data[0] & 63) << 7) | (data[1] >> 1)
# Account for the sign bit
if self.differential and result > 4095:
result = -(8192 - result)
assert -4096 <= result < 4096
return result
def _send(self):
return [16 + [8, 0][self.differential] + self.channel, 0, 0]
[docs]class MCP3001(MCP3xxx):
"""
The `MCP3001`_ is a 10-bit analog to digital converter with 1 channel
.. _MCP3001: http://www.farnell.com/datasheets/630400.pdf
"""
def __init__(self, **spi_args):
super(MCP3001, self).__init__(0, 10, differential=True, **spi_args)
[docs]class MCP3002(MCP3xxx):
"""
The `MCP3002`_ is a 10-bit analog to digital converter with 2 channels
(0-1).
.. _MCP3002: http://www.farnell.com/datasheets/1599363.pdf
"""
def __init__(self, channel=0, differential=False, **spi_args):
if not 0 <= channel < 2:
raise InputDeviceError('channel must be 0 or 1')
super(MCP3002, self).__init__(channel, 10, differential, **spi_args)
[docs]class MCP3004(MCP3xxx):
"""
The `MCP3004`_ is a 10-bit analog to digital converter with 4 channels
(0-3).
.. _MCP3004: http://www.farnell.com/datasheets/808965.pdf
"""
def __init__(self, channel=0, differential=False, **spi_args):
if not 0 <= channel < 4:
raise InputDeviceError('channel must be between 0 and 3')
super(MCP3004, self).__init__(channel, 10, differential, **spi_args)
[docs]class MCP3008(MCP3xxx):
"""
The `MCP3008`_ is a 10-bit analog to digital converter with 8 channels
(0-7).
.. _MCP3008: http://www.farnell.com/datasheets/808965.pdf
"""
def __init__(self, channel=0, differential=False, **spi_args):
if not 0 <= channel < 8:
raise InputDeviceError('channel must be between 0 and 7')
super(MCP3008, self).__init__(channel, 10, differential, **spi_args)
[docs]class MCP3201(MCP3xxx):
"""
The `MCP3201`_ is a 12-bit analog to digital converter with 1 channel
.. _MCP3201: http://www.farnell.com/datasheets/1669366.pdf
"""
def __init__(self, **spi_args):
super(MCP3201, self).__init__(0, 12, differential=True, **spi_args)
[docs]class MCP3202(MCP3xxx):
"""
The `MCP3202`_ is a 12-bit analog to digital converter with 2 channels
(0-1).
.. _MCP3202: http://www.farnell.com/datasheets/1669376.pdf
"""
def __init__(self, channel=0, differential=False, **spi_args):
if not 0 <= channel < 2:
raise InputDeviceError('channel must be 0 or 1')
super(MCP3202, self).__init__(channel, 12, differential, **spi_args)
[docs]class MCP3204(MCP3xxx):
"""
The `MCP3204`_ is a 12-bit analog to digital converter with 4 channels
(0-3).
.. _MCP3204: http://www.farnell.com/datasheets/808967.pdf
"""
def __init__(self, channel=0, differential=False, **spi_args):
if not 0 <= channel < 4:
raise InputDeviceError('channel must be between 0 and 3')
super(MCP3204, self).__init__(channel, 12, differential, **spi_args)
[docs]class MCP3208(MCP3xxx):
"""
The `MCP3208`_ is a 12-bit analog to digital converter with 8 channels
(0-7).
.. _MCP3208: http://www.farnell.com/datasheets/808967.pdf
"""
def __init__(self, channel=0, differential=False, **spi_args):
if not 0 <= channel < 8:
raise InputDeviceError('channel must be between 0 and 7')
super(MCP3208, self).__init__(channel, 12, differential, **spi_args)
[docs]class MCP3301(MCP33xx):
"""
The `MCP3301`_ is a signed 13-bit analog to digital converter. Please note
that the MCP3301 always operates in differential mode between its two
channels and the output value is scaled from -1 to +1.
.. _MCP3301: http://www.farnell.com/datasheets/1669397.pdf
"""
def __init__(self, **spi_args):
super(MCP3301, self).__init__(0, differential=True, **spi_args)
def _send(self):
return [0, 0]
[docs]class MCP3302(MCP33xx):
"""
The `MCP3302`_ is a 12/13-bit analog to digital converter with 4 channels
(0-3). When operated in differential mode, the device outputs a signed
13-bit value which is scaled from -1 to +1. When operated in single-ended
mode (the default), the device outputs an unsigned 12-bit value scaled from
0 to 1.
.. _MCP3302: http://www.farnell.com/datasheets/1486116.pdf
"""
def __init__(self, channel=0, differential=False, **spi_args):
if not 0 <= channel < 4:
raise InputDeviceError('channel must be between 0 and 4')
super(MCP3302, self).__init__(channel, differential, **spi_args)
[docs]class MCP3304(MCP33xx):
"""
The `MCP3304`_ is a 12/13-bit analog to digital converter with 8 channels
(0-7). When operated in differential mode, the device outputs a signed
13-bit value which is scaled from -1 to +1. When operated in single-ended
mode (the default), the device outputs an unsigned 12-bit value scaled from
0 to 1.
.. _MCP3304: http://www.farnell.com/datasheets/1486116.pdf
"""
def __init__(self, channel=0, differential=False, **spi_args):
if not 0 <= channel < 8:
raise InputDeviceError('channel must be between 0 and 7')
super(MCP3304, self).__init__(channel, differential, **spi_args)