Merge pull request #98 from RoaCode/comparator

Added Comparator functionality

Author: tannewt

.pre-commit-config.yaml

@@ -18,7 +18,7 @@ repos:
       - id: end-of-file-fixer
       - id: trailing-whitespace
   - repo: https://github.com/pycqa/pylint
-    rev: v2.17.4
+    rev: v3.2.6
     hooks:
       - id: pylint
         name: pylint (library code)

adafruit_ads1x15/ads1015.py

@@ -65,8 +65,9 @@ def rate_config(self) -> Dict[int, int]:
         return _ADS1015_CONFIG_DR
 
     def _data_rate_default(self) -> Literal[1600]:
+        """Default data rate setting is 1600 samples per second"""
         return 1600
 
     def _conversion_value(self, raw_adc: int) -> int:
         value = struct.unpack(">h", raw_adc.to_bytes(2, "big"))[0]
-        return value >> 4
+        return value

adafruit_ads1x15/ads1115.py

@@ -66,6 +66,7 @@ def rate_config(self) -> Dict[int, int]:
         return _ADS1115_CONFIG_DR
 
     def _data_rate_default(self) -> Literal[128]:
+        """Default data rate setting is 128 samples per second"""
         return 128
 
     def _conversion_value(self, raw_adc: int) -> int:

adafruit_ads1x15/ads1x15.py

@@ -33,9 +33,17 @@
 _ADS1X15_DEFAULT_ADDRESS = const(0x48)
 _ADS1X15_POINTER_CONVERSION = const(0x00)
 _ADS1X15_POINTER_CONFIG = const(0x01)
+_ADS1X15_POINTER_LO_THRES = const(0x02)
+_ADS1X15_POINTER_HI_THRES = const(0x03)
+
 _ADS1X15_CONFIG_OS_SINGLE = const(0x8000)
 _ADS1X15_CONFIG_MUX_OFFSET = const(12)
-_ADS1X15_CONFIG_COMP_QUE_DISABLE = const(0x0003)
+_ADS1X15_CONFIG_COMP_QUEUE = {
+    0: 0x0003,
+    1: 0x0000,
+    2: 0x0001,
+    4: 0x0002,
+}
 _ADS1X15_CONFIG_GAIN = {
     2 / 3: 0x0000,
     1: 0x0200,
@@ -66,15 +74,28 @@ class ADS1x15:
     :param int data_rate: The data rate for ADC conversion in samples per second.
                           Default value depends on the device.
     :param Mode mode: The conversion mode, defaults to `Mode.SINGLE`.
+    :param int comparator_queue_length: The number of successive conversions exceeding
+                          the comparator threshold before asserting ALERT/RDY pin.
+                          Defaults to 0 (comparator function disabled).
+    :param int comparator_low_threshold: Voltage limit under which comparator de-asserts
+                          ALERT/RDY pin. Must be lower than high threshold to use comparator
+                          function. See subclass for value range and default.
+    :param int comparator_high_threshold: Voltage limit over which comparator asserts
+                          ALERT/RDY pin. Must be higher than low threshold to use comparator
+                          function. See subclass for value range and default.
     :param int address: The I2C address of the device.
     """
 
+    # pylint: disable=too-many-instance-attributes
     def __init__(
         self,
         i2c: I2C,
         gain: float = 1,
         data_rate: Optional[int] = None,
         mode: int = Mode.SINGLE,
+        comparator_queue_length: int = 0,
+        comparator_low_threshold: int = -32768,
+        comparator_high_threshold: int = 32767,
         address: int = _ADS1X15_DEFAULT_ADDRESS,
     ):
         # pylint: disable=too-many-arguments
@@ -83,7 +104,10 @@ def __init__(
         self.gain = gain
         self.data_rate = self._data_rate_default() if data_rate is None else data_rate
         self.mode = mode
+        self.comparator_queue_length = comparator_queue_length
         self.i2c_device = I2CDevice(i2c, address)
+        self.comparator_low_threshold = comparator_low_threshold
+        self.comparator_high_threshold = comparator_high_threshold
 
     @property
     def bits(self) -> int:
@@ -131,6 +155,67 @@ def gains(self) -> List[float]:
         g.sort()
         return g
 
+    @property
+    def comparator_queue_length(self) -> int:
+        """The ADC comparator queue length."""
+        return self._comparator_queue_length
+
+    @comparator_queue_length.setter
+    def comparator_queue_length(self, comparator_queue_length: int) -> None:
+        possible_comp_queue_lengths = self.comparator_queue_lengths
+        if comparator_queue_length not in possible_comp_queue_lengths:
+            raise ValueError(
+                "Comparator Queue must be one of: {}".format(
+                    possible_comp_queue_lengths
+                )
+            )
+        self._comparator_queue_length = comparator_queue_length
+
+    @property
+    def comparator_queue_lengths(self) -> List[int]:
+        """Possible comparator queue length settings."""
+        g = list(_ADS1X15_CONFIG_COMP_QUEUE.keys())
+        g.sort()
+        return g
+
+    @property
+    def comparator_low_threshold(self) -> int:
+        """The ADC Comparator Lower Limit Threshold."""
+        return self._comparator_low_threshold
+
+    @property
+    def comparator_high_threshold(self) -> int:
+        """The ADC Comparator Higher Limit Threshold."""
+        return self._comparator_high_threshold
+
+    @comparator_low_threshold.setter
+    def comparator_low_threshold(self, value: int) -> None:
+        """Set comparator low threshold value for ADS1x15 ADC
+
+        :param int value: 16-bit signed integer to write to register
+        """
+        if value < -32768 or value > 32767:
+            raise ValueError(
+                "Comparator Threshold value must be between -32768 and 32767"
+            )
+
+        self._comparator_low_threshold = value
+        self._write_register(_ADS1X15_POINTER_LO_THRES, self.comparator_low_threshold)
+
+    @comparator_high_threshold.setter
+    def comparator_high_threshold(self, value: int) -> None:
+        """Set comparator high threshold value for ADS1x15 ADC
+
+        :param int value: 16-bit signed integer to write to register
+        """
+        if value < -32768 or value > 32767:
+            raise ValueError(
+                "Comparator Threshold value must be between -32768 and 32767"
+            )
+
+        self._comparator_high_threshold = value
+        self._write_register(_ADS1X15_POINTER_HI_THRES, self.comparator_high_threshold)
+
     @property
     def mode(self) -> int:
         """The ADC conversion mode."""
@@ -183,7 +268,7 @@ def _read(self, pin: Pin) -> int:
         config |= _ADS1X15_CONFIG_GAIN[self.gain]
         config |= self.mode
         config |= self.rate_config[self.data_rate]
-        config |= _ADS1X15_CONFIG_COMP_QUE_DISABLE
+        config |= _ADS1X15_CONFIG_COMP_QUEUE[self.comparator_queue_length]
         self._write_register(_ADS1X15_POINTER_CONFIG, config)
 
         # Wait for conversion to complete

adafruit_ads1x15/analog_in.py

@@ -55,12 +55,31 @@ def value(self) -> int:
         Even if the underlying analog to digital converter (ADC) is
         lower resolution, the value is 16-bit.
         """
-        return self._ads.read(
-            self._pin_setting, is_differential=self.is_differential
-        ) << (16 - self._ads.bits)
+        return self._ads.read(self._pin_setting, is_differential=self.is_differential)
 
     @property
     def voltage(self) -> float:
         """Returns the voltage from the ADC pin as a floating point value."""
-        volts = self.value * _ADS1X15_PGA_RANGE[self._ads.gain] / 32767
+        volts = self.convert_to_voltage(self.value)
+        return volts
+
+    def convert_to_value(self, volts: float) -> int:
+        """Calculates a standard 16-bit integer value for a given voltage"""
+
+        lsb = _ADS1X15_PGA_RANGE[self._ads.gain] / (1 << (self._ads.bits - 1))
+        value = int(volts / lsb)
+
+        # Need to bit shift if value is only 12-bits
+        value <<= 16 - self._ads.bits
+        return value
+
+    def convert_to_voltage(self, value_int: int) -> float:
+        """Calculates voltage from 16-bit ADC reading"""
+
+        lsb = _ADS1X15_PGA_RANGE[self._ads.gain] / (1 << (self._ads.bits - 1))
+
+        # Need to bit shift if value is only 12-bits
+        value_int >>= 16 - self._ads.bits
+        volts = value_int * lsb
+
         return volts

examples/ads1x15_comparator_example.py

@@ -0,0 +1,43 @@
+# SPDX-FileCopyrightText: 2021 ladyada for Adafruit Industries
+# SPDX-License-Identifier: MIT
+
+import time
+import board
+import busio
+import countio
+
+import adafruit_ads1x15.ads1015 as ADS
+
+# import adafruit_ads1x15.ads1115 as ADS
+from adafruit_ads1x15.analog_in import AnalogIn
+
+# Create the I2C bus
+i2c = busio.I2C(board.SCL, board.SDA)
+
+# Create the ADS object
+ads = ADS.ADS1015(i2c)
+# ads = ADS.ADS1115(i2c)
+
+# Create a single-ended channel on Pin 0
+#   Max counts for ADS1015 = 2047
+#                  ADS1115 = 32767
+chan = AnalogIn(ads, ADS.P0)
+
+# Create Interrupt-driven input to track comparator changes
+int_pin = countio.Counter(board.GP9, edge=countio.Edge.RISE)
+
+# Set comparator to assert after 1 ADC conversion
+ads.comparator_queue_length = 1
+
+# Set comparator low threshold to 2V
+ads.comparator_low_threshold = chan.convert_to_value(2.000)
+# Set comparator high threshold to 2.002V. High threshold must be above low threshold
+ads.comparator_high_threshold = chan.convert_to_value(2.002)
+
+count = 0
+while True:
+    print(chan.value, chan.voltage)  # This initiates new ADC reading
+    if int_pin.count > count:
+        print("Comparator Triggered")
+        count = int_pin.count
+    time.sleep(2)