Change pressure sensor from built in adc to external i2c adc.

2 years ago · 2824211898
4 changed files with 281 additions and 15 deletions
--- a/src/ads1x15.py
+++ b/src/ads1x15.py
@ -0,0 +1,252 @@
+# The MIT License (MIT)
+#
+# Copyright (c) 2016 Radomir Dopieralski (@deshipu),
+#               2017 Robert Hammelrath (@robert-hh)
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+# THE SOFTWARE.
+#
+import utime as time
+
+_REGISTER_MASK = const(0x03)
+_REGISTER_CONVERT = const(0x00)
+_REGISTER_CONFIG = const(0x01)
+_REGISTER_LOWTHRESH = const(0x02)
+_REGISTER_HITHRESH = const(0x03)
+
+_OS_MASK = const(0x8000)
+_OS_SINGLE = const(0x8000)  # Write: Set to start a single-conversion
+_OS_BUSY = const(0x0000)  # Read: Bit=0 when conversion is in progress
+_OS_NOTBUSY = const(0x8000)  # Read: Bit=1 when no conversion is in progress
+
+_MUX_MASK = const(0x7000)
+_MUX_DIFF_0_1 = const(0x0000)  # Differential P  =  AIN0, N  =  AIN1 (default)
+_MUX_DIFF_0_3 = const(0x1000)  # Differential P  =  AIN0, N  =  AIN3
+_MUX_DIFF_1_3 = const(0x2000)  # Differential P  =  AIN1, N  =  AIN3
+_MUX_DIFF_2_3 = const(0x3000)  # Differential P  =  AIN2, N  =  AIN3
+_MUX_SINGLE_0 = const(0x4000)  # Single-ended AIN0
+_MUX_SINGLE_1 = const(0x5000)  # Single-ended AIN1
+_MUX_SINGLE_2 = const(0x6000)  # Single-ended AIN2
+_MUX_SINGLE_3 = const(0x7000)  # Single-ended AIN3
+
+_PGA_MASK = const(0x0E00)
+_PGA_6_144V = const(0x0000)  # +/-6.144V range  =  Gain 2/3
+_PGA_4_096V = const(0x0200)  # +/-4.096V range  =  Gain 1
+_PGA_2_048V = const(0x0400)  # +/-2.048V range  =  Gain 2 (default)
+_PGA_1_024V = const(0x0600)  # +/-1.024V range  =  Gain 4
+_PGA_0_512V = const(0x0800)  # +/-0.512V range  =  Gain 8
+_PGA_0_256V = const(0x0A00)  # +/-0.256V range  =  Gain 16
+
+_MODE_MASK = const(0x0100)
+_MODE_CONTIN = const(0x0000)  # Continuous conversion mode
+_MODE_SINGLE = const(0x0100)  # Power-down single-shot mode (default)
+
+_DR_MASK = const(0x00E0)     # Values ADS1015/ADS1115
+_DR_128SPS = const(0x0000)   # 128 /8 samples per second
+_DR_250SPS = const(0x0020)   # 250 /16 samples per second
+_DR_490SPS = const(0x0040)   # 490 /32 samples per second
+_DR_920SPS = const(0x0060)   # 920 /64 samples per second
+_DR_1600SPS = const(0x0080)  # 1600/128 samples per second (default)
+_DR_2400SPS = const(0x00A0)  # 2400/250 samples per second
+_DR_3300SPS = const(0x00C0)  # 3300/475 samples per second
+_DR_860SPS = const(0x00E0)  # -   /860 samples per Second
+
+_CMODE_MASK = const(0x0010)
+_CMODE_TRAD = const(0x0000)  # Traditional comparator with hysteresis (default)
+_CMODE_WINDOW = const(0x0010)  # Window comparator
+
+_CPOL_MASK = const(0x0008)
+_CPOL_ACTVLOW = const(0x0000)  # ALERT/RDY pin is low when active (default)
+_CPOL_ACTVHI = const(0x0008)  # ALERT/RDY pin is high when active
+
+_CLAT_MASK = const(0x0004)  # Determines if ALERT/RDY pin latches once asserted
+_CLAT_NONLAT = const(0x0000)  # Non-latching comparator (default)
+_CLAT_LATCH = const(0x0004)  # Latching comparator
+
+_CQUE_MASK = const(0x0003)
+_CQUE_1CONV = const(0x0000)  # Assert ALERT/RDY after one conversions
+_CQUE_2CONV = const(0x0001)  # Assert ALERT/RDY after two conversions
+_CQUE_4CONV = const(0x0002)  # Assert ALERT/RDY after four conversions
+# Disable the comparator and put ALERT/RDY in high state (default)
+_CQUE_NONE = const(0x0003)
+
+_GAINS = (
+    _PGA_6_144V,  # 2/3x
+    _PGA_4_096V,  # 1x
+    _PGA_2_048V,  # 2x
+    _PGA_1_024V,  # 4x
+    _PGA_0_512V,  # 8x
+    _PGA_0_256V   # 16x
+)
+
+_GAINS_V = (
+    6.144,  # 2/3x
+    4.096,  # 1x
+    2.048,  # 2x
+    1.024,  # 4x
+    0.512,  # 8x
+    0.256  # 16x
+)
+
+_CHANNELS = {
+    (0, None): _MUX_SINGLE_0,
+    (1, None): _MUX_SINGLE_1,
+    (2, None): _MUX_SINGLE_2,
+    (3, None): _MUX_SINGLE_3,
+    (0, 1): _MUX_DIFF_0_1,
+    (0, 3): _MUX_DIFF_0_3,
+    (1, 3): _MUX_DIFF_1_3,
+    (2, 3): _MUX_DIFF_2_3,
+}
+
+_RATES = (
+    _DR_128SPS,   # 128/8 samples per second
+    _DR_250SPS,   # 250/16 samples per second
+    _DR_490SPS,   # 490/32 samples per second
+    _DR_920SPS,   # 920/64 samples per second
+    _DR_1600SPS,  # 1600/128 samples per second (default)
+    _DR_2400SPS,  # 2400/250 samples per second
+    _DR_3300SPS,  # 3300/475 samples per second
+    _DR_860SPS    # - /860 samples per Second
+)
+
+
+class ADS1115:
+    def __init__(self, i2c, address=0x48, gain=1):
+        self.i2c = i2c
+        self.address = address
+        self.gain = gain
+        self.temp2 = bytearray(2)
+
+    def _write_register(self, register, value):
+        self.temp2[0] = value >> 8
+        self.temp2[1] = value & 0xff
+        self.i2c.writeto_mem(self.address, register, self.temp2)
+
+    def _read_register(self, register):
+        self.i2c.readfrom_mem_into(self.address, register, self.temp2)
+        return (self.temp2[0] << 8) | self.temp2[1]
+
+    def raw_to_v(self, raw):
+        v_p_b = _GAINS_V[self.gain] / 32767
+        return raw * v_p_b
+
+    def set_conv(self, rate=4, channel1=0, channel2=None):
+        """Set mode for read_rev"""
+        self.mode = (_CQUE_NONE | _CLAT_NONLAT |
+                     _CPOL_ACTVLOW | _CMODE_TRAD | _RATES[rate] |
+                     _MODE_SINGLE | _OS_SINGLE | _GAINS[self.gain] |
+                     _CHANNELS[(channel1, channel2)])
+
+    def read(self, rate=4, channel1=0, channel2=None):
+        """Read voltage between a channel and GND.
+           Time depends on conversion rate."""
+        self._write_register(_REGISTER_CONFIG, (_CQUE_NONE | _CLAT_NONLAT |
+                             _CPOL_ACTVLOW | _CMODE_TRAD | _RATES[rate] |
+                             _MODE_SINGLE | _OS_SINGLE | _GAINS[self.gain] |
+                             _CHANNELS[(channel1, channel2)]))
+        while not self._read_register(_REGISTER_CONFIG) & _OS_NOTBUSY:
+            time.sleep_ms(1)
+        res = self._read_register(_REGISTER_CONVERT)
+        return res if res < 32768 else res - 65536
+
+    def read_rev(self):
+        """Read voltage between a channel and GND. and then start
+           the next conversion."""
+        res = self._read_register(_REGISTER_CONVERT)
+        self._write_register(_REGISTER_CONFIG, self.mode)
+        return res if res < 32768 else res - 65536
+
+    def alert_start(self, rate=4, channel1=0, channel2=None,
+                    threshold_high=0x4000, threshold_low=0, latched=False) :
+        """Start continuous measurement, set ALERT pin on threshold."""
+        self._write_register(_REGISTER_LOWTHRESH, threshold_low)
+        self._write_register(_REGISTER_HITHRESH, threshold_high)
+        self._write_register(_REGISTER_CONFIG, _CQUE_1CONV |
+                             _CLAT_LATCH if latched else _CLAT_NONLAT |
+                             _CPOL_ACTVLOW | _CMODE_TRAD | _RATES[rate] |
+                             _MODE_CONTIN | _GAINS[self.gain] |
+                             _CHANNELS[(channel1, channel2)])
+
+    def conversion_start(self, rate=4, channel1=0, channel2=None):
+        """Start continuous measurement, trigger on ALERT/RDY pin."""
+        self._write_register(_REGISTER_LOWTHRESH, 0)
+        self._write_register(_REGISTER_HITHRESH, 0x8000)
+        self._write_register(_REGISTER_CONFIG, _CQUE_1CONV | _CLAT_NONLAT |
+                             _CPOL_ACTVLOW | _CMODE_TRAD | _RATES[rate] |
+                             _MODE_CONTIN | _GAINS[self.gain] |
+                             _CHANNELS[(channel1, channel2)])
+
+    def alert_read(self):
+        """Get the last reading from the continuous measurement."""
+        res = self._read_register(_REGISTER_CONVERT)
+        return res if res < 32768 else res - 65536
+
+
+class ADS1113(ADS1115):
+    def __init__(self, i2c, address=0x48):
+        super().__init__(i2c, address, 1)
+
+    def raw_to_v(self, raw):
+        return super().raw_to_v(raw)
+
+    def read(self, rate=4):
+        return super().read(rate, 0, 1)
+
+    def alert_start(self, rate=4, threshold_high=0x4000, threshold_low=0, latched=False):
+        return super().alert_start(rate, 0, 1, threshold_high, threshold_low, latched)
+
+    def alert_read(self):
+        return super().alert_read()
+
+
+class ADS1114(ADS1115):
+    def __init__(self, i2c, address=0x48, gain=1):
+        super().__init__(i2c, address, gain)
+
+    def raw_to_v(self, raw):
+        return super().raw_to_v(raw)
+
+    def read(self, rate=4):
+        return super().read(rate, 0, 1)
+
+    def alert_start(self, rate=4, threshold_high=0x4000, threshold_low=0, latched=False):
+        return super().alert_start(rate, 0, 1, threshold_high,
+            threshold_low, latched)
+
+    def alert_read(self):
+        return super().alert_read()
+
+
+class ADS1015(ADS1115):
+    def __init__(self, i2c, address=0x48, gain=1):
+        super().__init__(i2c, address, gain)
+
+    def raw_to_v(self, raw):
+        return super().raw_to_v(raw << 4)
+
+    def read(self, rate=4, channel1=0, channel2=None):
+        return super().read(rate, channel1, channel2) >> 4
+
+    def alert_start(self, rate=4, channel1=0, channel2=None, threshold_high=0x400,
+        threshold_low=0, latched=False):
+        return super().alert_start(rate, channel1, channel2, threshold_high << 4,
+            threshold_low << 4, latched)
+
+    def alert_read(self):
+        return super().alert_read() >> 4
--- a/src/constants.py
+++ b/src/constants.py
@ -1,15 +1,17 @@
 """RASPBERRY PICO PINS"""
 """PINOUTS"""
-PRESSURE_SENSOR_PIN = 26
 HALL_SENSOR_PIN = 27
 RESET_BUTTON_PIN = 22
 BUZZER_PIN = 15
+ALARM_LED_PIN = 26
 LCD_SDA = 0
 LCD_SCL = 1
+PRESSURE_SENSOR_ADC_SDA = 10
+PRESSURE_SENSOR_ADC_SCL = 11


 """FIXED NUMBERS"""
 ANNOYTING_BUZZER_TONE = 51250
 NORMAL_BUZZER_TONE = 200
-ADC_RESOLUTION = 65535.0
-MAX_VOTLAGE = 3.3
+ADC_RESOLUTION = 32768.0
+MAX_PRESSURE_SENSOR_VOTLAGE = 6.144
--- a/src/pressure_sensor.py
+++ b/src/pressure_sensor.py
@ -1,14 +1,26 @@
-from machine import ADC, Pin
+from machine import I2C, Pin, Timer
+import ads1x15 
+
 import constants
 import parameters


-pressure_sensor = ADC(Pin(constants.PRESSURE_SENSOR_PIN, mode=Pin.IN))
+class PressureSensor:
+
+    _I2C = I2C(1, scl=Pin(constants.PRESSURE_SENSOR_ADC_SCL), sda=Pin(constants.PRESSURE_SENSOR_ADC_SDA), freq=400000)
+    _I2C_ADDR = _I2C.scan()[0]
+    _ADC = ads1x15.ADS1115(_I2C, _I2C_ADDR, 0)
+    _SMOOTH_FACTOR = parameters.PRESSURE_SMOOTH_LENGTH * constants.ADC_RESOLUTION / constants.MAX_PRESSURE_SENSOR_VOTLAGE
+
+    @staticmethod
+    def read():
+        measure = PressureSensor._ADC.read(0)
+        return measure

-def get_pressure():
-    global pressure_sensor
-    pressure_value = 0
-    for i in range(parameters.PRESSURE_SMOOTH_LENGTH):
-        pressure_value += pressure_sensor.read_u16()
-    pressure_measure = float(pressure_value) / parameters.PRESSURE_SMOOTH_LENGTH / constants.ADC_RESOLUTION * constants.MAX_VOTLAGE
-    return pressure_measure
+    @staticmethod
+    def get_pressure():
+        pressure_value = 0
+        for i in range(parameters.PRESSURE_SMOOTH_LENGTH):
+            pressure_value += PressureSensor.read()
+        pressure_measure = float(pressure_value) / PressureSensor._SMOOTH_FACTOR
+        return pressure_measure
--- a/src/states.py
+++ b/src/states.py
@ -1,6 +1,6 @@
 import time
 import hall_sensor
-import pressure_sensor
+from pressure_sensor import PressureSensor
 import parameters
 from alarm import Alarm

@ -8,7 +8,7 @@ from alarm import Alarm
 class StateMachine:

    def __init__(self) -> None:
-        self.previous_pressure = pressure_sensor.get_pressure()
+        self.previous_pressure = PressureSensor.get_pressure()
        time.sleep(0.02)
        self.__measure_pressure()
        
@ -23,7 +23,7 @@ class StateMachine:
            time.sleep(0.03)

    def __measure_pressure(self):
-        self.current_pressure = pressure_sensor.get_pressure()
+        self.current_pressure = PressureSensor.get_pressure()

    def handle_pressure(self):
        self.__measure_pressure()