Added Comparator functionality

adafruit_ads1x15/ads1x15.py

@@ -1,4 +1,4 @@
 # SPDX-FileCopyrightText: 2018 Carter Nelson for Adafruit Industries
 #
 # SPDX-License-Identifier: MIT
 
@@ -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,
@@ -58,7 +66,7 @@
     """Single-Shot Mode"""
 
 
 class ADS1x15:
     """Base functionality for ADS1x15 analog to digital converters.
 
     :param ~busio.I2C i2c: The I2C bus the device is connected to.
@@ -66,6 +74,9 @@
     :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_thres: Voltage limit under which comparator de-asserts ALERT/RDY pin. Must be lower than high threshold to use comparator function. Defaults to 0x800.
+    :param int comparator_high_thres: Voltage limit over which comparator asserts ALERT/RDY pin. Must be higher than low threshold to use comparator function. Defaults to 0x7FF.
     :param int address: The I2C address of the device.
     """
 
@@ -75,6 +86,9 @@
         gain: float = 1,
         data_rate: Optional[int] = None,
         mode: int = Mode.SINGLE,
+        comparator_queue_length: int = 0,
+        comparator_low_thres: int = 0x8000,
+        comparator_high_thres: int = 0x7FF0,
         address: int = _ADS1X15_DEFAULT_ADDRESS,
     ):
         # pylint: disable=too-many-arguments
@@ -83,6 +97,9 @@
         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.comparator_low_thres: comparator_low_thres
+        self.comparator_high_thres: comparator_high_thres
         self.i2c_device = I2CDevice(i2c, address)
 
     @property
@@ -131,6 +148,49 @@
         g.sort()
         return g
 
+    @property
+    def comparator_queue_length(self) -> int:
+        """The ADC Comparator Queue."""
+        return self._comparator_queue_length
+
+    @comparator_queue_length.setter
+    def comparator_queue_length(self, comparator_queue_length: int) -> None:
+        possible_comparator_queue_lengths = self.comparator_queue_lengths
+        if comparator_queue_length not in possible_comparator_queue_lengths:
+            raise ValueError("Comparator Queue must be one of: {}".format(possible_comparator_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_thres(self) -> int:
+        """The ADC Comparator Lower Limit Threshold."""
+        return self._comparator_low_thres
+
+    @comparator_low_thres.setter
+    def comparator_low_thres(self, comparator_low_thres: int) -> None:
+        """Sets 12-bit threshold in 16-bit register in unsigned format."""
+        if comparator_low_thres < 0 or comparator_low_thres > 65535:
+            raise ValueError("Comparator Low Threshold must be unsigned 16-bit integer between 0 and 65535")
+        self._comparator_low_thres = comparator_low_thres
+
+    @property
+    def comparator_high_thres(self) -> int:
+        """The ADC Comparator Higher Limit Threshold."""
+        return self._comparator_high_thres
+
+    @comparator_high_thres.setter
+    def comparator_high_thres(self, comparator_high_thres: int) -> None:
+        """Sets 12-bit threshold in 16-bit register in unsigned format."""
+        if comparator_high_thres < 0 or comparator_high_thres > 65535:
+            raise ValueError("Comparator High Threshold must be unsigned 16-bit integer between 0 and 65535")
+        self._comparator_high_thres = comparator_high_thres
+
     @property
     def mode(self) -> int:
         """The ADC conversion mode."""
@@ -183,7 +243,7 @@
         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
@@ -222,6 +282,20 @@
         with self.i2c_device as i2c:
             i2c.write(self.buf)
 
+    def write_comparator_thresholds(self):
+        """Write 16 bit values to Comparator Low and High Threshold registers."""
+        self.buf[0] = _ADS1X15_POINTER_LO_THRES
+        self.buf[1] = (self._comparator_low_thres >> 8) & 0xFF
+        self.buf[2] = self._comparator_low_thres & 0xFF
+        with self.i2c_device as i2c:
+            i2c.write(self.buf)
+
+        self.buf[0] = _ADS1X15_POINTER_HI_THRES
+        self.buf[1] = (self._comparator_high_thres >> 8) & 0xFF
+        self.buf[2] = self._comparator_high_thres & 0xFF
+        with self.i2c_device as i2c:
+            i2c.write(self.buf)
+
     def _read_register(self, reg: int, fast: bool = False) -> int:
         """Read 16 bit register value. If fast is True, the pointer register
         is not updated.

adafruit_ads1x15/analog_in.py

@@ -62,5 +62,19 @@
     @property
     def voltage(self) -> float:
         """Returns the voltage from the ADC pin as a floating point value."""
+        volts = self.convert_to_voltage(self.value)
+        return volts
+
+    def convert_to_value(self, volts: float) -> int:
+        """Calculates integer for threshold registers from voltage level input"""
+        value = round((volts * 32767) / _ADS1X15_PGA_RANGE[self._ads.gain])
+        if value < 0:
+            value = 65536 + value
+        return value
+
+    def convert_to_voltage(self, value: int) -> float:
+        """Calculates integer for threshold registers from voltage level input"""
         volts = self.value * _ADS1X15_PGA_RANGE[self._ads.gain] / 32767
+        if volts > _ADS1X15_PGA_RANGE[self._ads.gain]:
+            volts = _ADS1X15_PGA_RANGE[self._ads.gain] - volts
         return volts

examples/ads1x15_comparator_example.py

@@ -0,0 +1,44 @@
+# 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_thres = chan.convert_to_value(2.000)
+# Set comparator high threshold to 2.002V. High threshold must be above low threshold
+ads.comparator_high_thres = chan.convert_to_value(2.002)
+# Write comparator values to the chip registers
+ads.write_comparator_thresholds()
+
+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)