Add available() method to gas sensor

This change catches an IOError when setting up the gas sensor and provides an `available()` method for determining if a sensor is present.

Author: Gadgetoid

library/enviroplus/gas.py

@@ -10,6 +10,7 @@
 
 ads1015.I2C_ADDRESS_DEFAULT = ads1015.I2C_ADDRESS_ALTERNATE
 _is_setup = False
+_is_available = False
 _adc_enabled = False
 _adc_gain = 6.148
 
@@ -41,13 +42,19 @@ def __repr__(self):
 
 
 def setup():
-    global adc, adc_type, _is_setup
+    global adc, adc_type, _is_setup, _is_available
     if _is_setup:
         return
     _is_setup = True
 
-    adc = ads1015.ADS1015(i2c_addr=0x49)
-    adc_type = adc.detect_chip_type()
+    try:
+        adc = ads1015.ADS1015(i2c_addr=0x49)
+        adc_type = adc.detect_chip_type()
+        _is_available = True
+    except IOError:
+        _is_available = False
+        return
+
     adc.set_mode('single')
     adc.set_programmable_gain(MICS6814_GAIN)
     if adc_type == 'ADS1115':
@@ -62,6 +69,11 @@ def setup():
     atexit.register(cleanup)
 
 
+def available():
+    setup()
+    return _is_available
+
+
 def enable_adc(value=True):
     """Enable reading from the additional ADC pin."""
     global _adc_enabled
@@ -81,6 +93,10 @@ def cleanup():
 def read_all():
     """Return gas resistence for oxidising, reducing and NH3"""
     setup()
+
+    if not _is_available:
+        raise RuntimeError("Gas sensor not connected.")
+
     ox = adc.get_voltage('in0/gnd')
     red = adc.get_voltage('in1/gnd')
     nh3 = adc.get_voltage('in2/gnd')
@@ -119,7 +135,6 @@ def read_oxidising():
 
     Eg chlorine, nitrous oxide
     """
-    setup()
     return read_all().oxidising
 
 
@@ -128,17 +143,14 @@ def read_reducing():
 
     Eg hydrogen, carbon monoxide
     """
-    setup()
     return read_all().reducing
 
 
 def read_nh3():
     """Return gas resistance for nh3/ammonia"""
-    setup()
     return read_all().nh3
 
 
 def read_adc():
     """Return spare ADC channel value"""
-    setup()
     return read_all().adc

library/tests/conftest.py

@@ -1,90 +1,99 @@
-"""Test configuration.
-These allow the mocking of various Python modules
-that might otherwise have runtime side-effects.
-"""
-import sys
-import mock
-import pytest
-from i2cdevice import MockSMBus
-
-
-class SMBusFakeDevice(MockSMBus):
-    def __init__(self, i2c_bus):
-        MockSMBus.__init__(self, i2c_bus)
-        self.regs[0x00:0x01] = 0x0f, 0x00
-
-
-@pytest.fixture(scope='function', autouse=True)
-def cleanup():
-    yield None
-    try:
-        del sys.modules['enviroplus']
-    except KeyError:
-        pass
-    try:
-        del sys.modules['enviroplus.noise']
-    except KeyError:
-        pass
-    try:
-        del sys.modules['enviroplus.gas']
-    except KeyError:
-        pass
-
-
-@pytest.fixture(scope='function', autouse=False)
-def GPIO():
-    """Mock RPi.GPIO module."""
-    GPIO = mock.MagicMock()
-    # Fudge for Python < 37 (possibly earlier)
-    sys.modules['RPi'] = mock.Mock()
-    sys.modules['RPi'].GPIO = GPIO
-    sys.modules['RPi.GPIO'] = GPIO
-    yield GPIO
-    del sys.modules['RPi']
-    del sys.modules['RPi.GPIO']
-
-
-@pytest.fixture(scope='function', autouse=False)
-def spidev():
-    """Mock spidev module."""
-    spidev = mock.MagicMock()
-    sys.modules['spidev'] = spidev
-    yield spidev
-    del sys.modules['spidev']
-
-
-@pytest.fixture(scope='function', autouse=False)
-def smbus():
-    """Mock smbus module."""
-    smbus = mock.MagicMock()
-    smbus.SMBus = SMBusFakeDevice
-    sys.modules['smbus'] = smbus
-    yield smbus
-    del sys.modules['smbus']
-
-
-@pytest.fixture(scope='function', autouse=False)
-def atexit():
-    """Mock atexit module."""
-    atexit = mock.MagicMock()
-    sys.modules['atexit'] = atexit
-    yield atexit
-    del sys.modules['atexit']
-
-
-@pytest.fixture(scope='function', autouse=False)
-def sounddevice():
-    """Mock sounddevice module."""
-    sounddevice = mock.MagicMock()
-    sys.modules['sounddevice'] = sounddevice
-    yield sounddevice
-    del sys.modules['sounddevice']
-
-
-@pytest.fixture(scope='function', autouse=False)
-def numpy():
-    """Mock numpy module."""
-    numpy = mock.MagicMock()
-    sys.modules['numpy'] = numpy
-    yield numpy
-    del sys.modules['numpy']
+"""Test configuration.
+These allow the mocking of various Python modules
+that might otherwise have runtime side-effects.
+"""
+import sys
+import mock
+import pytest
+from i2cdevice import MockSMBus
+
+
+class SMBusFakeDevice(MockSMBus):
+    def __init__(self, i2c_bus):
+        MockSMBus.__init__(self, i2c_bus)
+        self.regs[0x00:0x01] = 0x0f, 0x00
+
+
+@pytest.fixture(scope='function', autouse=True)
+def cleanup():
+    yield None
+    try:
+        del sys.modules['enviroplus']
+    except KeyError:
+        pass
+    try:
+        del sys.modules['enviroplus.noise']
+    except KeyError:
+        pass
+    try:
+        del sys.modules['enviroplus.gas']
+    except KeyError:
+        pass
+
+
+@pytest.fixture(scope='function', autouse=False)
+def GPIO():
+    """Mock RPi.GPIO module."""
+    GPIO = mock.MagicMock()
+    # Fudge for Python < 37 (possibly earlier)
+    sys.modules['RPi'] = mock.Mock()
+    sys.modules['RPi'].GPIO = GPIO
+    sys.modules['RPi.GPIO'] = GPIO
+    yield GPIO
+    del sys.modules['RPi']
+    del sys.modules['RPi.GPIO']
+
+
+@pytest.fixture(scope='function', autouse=False)
+def spidev():
+    """Mock spidev module."""
+    spidev = mock.MagicMock()
+    sys.modules['spidev'] = spidev
+    yield spidev
+    del sys.modules['spidev']
+
+
+@pytest.fixture(scope='function', autouse=False)
+def smbus():
+    """Mock smbus module."""
+    smbus = mock.MagicMock()
+    smbus.SMBus = SMBusFakeDevice
+    sys.modules['smbus'] = smbus
+    yield smbus
+    del sys.modules['smbus']
+
+
+@pytest.fixture(scope='function', autouse=False)
+def mocksmbus():
+    """Mock smbus module."""
+    smbus = mock.MagicMock()
+    sys.modules['smbus'] = smbus
+    yield smbus
+    del sys.modules['smbus']
+
+
+@pytest.fixture(scope='function', autouse=False)
+def atexit():
+    """Mock atexit module."""
+    atexit = mock.MagicMock()
+    sys.modules['atexit'] = atexit
+    yield atexit
+    del sys.modules['atexit']
+
+
+@pytest.fixture(scope='function', autouse=False)
+def sounddevice():
+    """Mock sounddevice module."""
+    sounddevice = mock.MagicMock()
+    sys.modules['sounddevice'] = sounddevice
+    yield sounddevice
+    del sys.modules['sounddevice']
+
+
+@pytest.fixture(scope='function', autouse=False)
+def numpy():
+    """Mock numpy module."""
+    numpy = mock.MagicMock()
+    sys.modules['numpy'] = numpy
+    yield numpy
+    del sys.modules['numpy']

library/tests/test_noise.py

@@ -1,48 +1,48 @@
-import pytest
-
-
-def test_noise_setup(sounddevice, numpy):
-    from enviroplus.noise import Noise
-
-    noise = Noise(sample_rate=16000, duration=0.1)
-    del noise
-
-
-def test_noise_get_amplitudes_at_frequency_ranges(sounddevice, numpy):
-    from enviroplus.noise import Noise
-
-    noise = Noise(sample_rate=16000, duration=0.1)
-    noise.get_amplitudes_at_frequency_ranges([
-        (100, 500),
-        (501, 1000)
-    ])
-
-    sounddevice.rec.assert_called_with(0.1 * 16000, samplerate=16000, blocking=True, channels=1, dtype='float64')
-
-
-def test_noise_get_noise_profile(sounddevice, numpy):
-    from enviroplus.noise import Noise
-
-    numpy.mean.return_value = 10.0
-
-    noise = Noise(sample_rate=16000, duration=0.1)
-    amp_low, amp_mid, amp_high, amp_total = noise.get_noise_profile(
-        noise_floor=100,
-        low=0.12,
-        mid=0.36,
-        high=None)
-
-    sounddevice.rec.assert_called_with(0.1 * 16000, samplerate=16000, blocking=True, channels=1, dtype='float64')
-
-    assert amp_total == 10.0
-
-
-def test_get_amplitude_at_frequency_range(sounddevice, numpy):
-    from enviroplus.noise import Noise
-
-    noise = Noise(sample_rate=16000, duration=0.1)
-
-    noise.get_amplitude_at_frequency_range(0, 8000)
-
-    with pytest.raises(ValueError):
-        noise.get_amplitude_at_frequency_range(0, 16000)
+import pytest
+
+
+def test_noise_setup(sounddevice, numpy):
+    from enviroplus.noise import Noise
+
+    noise = Noise(sample_rate=16000, duration=0.1)
+    del noise
+
+
+def test_noise_get_amplitudes_at_frequency_ranges(sounddevice, numpy):
+    from enviroplus.noise import Noise
+
+    noise = Noise(sample_rate=16000, duration=0.1)
+    noise.get_amplitudes_at_frequency_ranges([
+        (100, 500),
+        (501, 1000)
+    ])
+
+    sounddevice.rec.assert_called_with(0.1 * 16000, samplerate=16000, blocking=True, channels=1, dtype='float64')
+
+
+def test_noise_get_noise_profile(sounddevice, numpy):
+    from enviroplus.noise import Noise
+
+    numpy.mean.return_value = 10.0
+
+    noise = Noise(sample_rate=16000, duration=0.1)
+    amp_low, amp_mid, amp_high, amp_total = noise.get_noise_profile(
+        noise_floor=100,
+        low=0.12,
+        mid=0.36,
+        high=None)
+
+    sounddevice.rec.assert_called_with(0.1 * 16000, samplerate=16000, blocking=True, channels=1, dtype='float64')
+
+    assert amp_total == 10.0
+
+
+def test_get_amplitude_at_frequency_range(sounddevice, numpy):
+    from enviroplus.noise import Noise
+
+    noise = Noise(sample_rate=16000, duration=0.1)
+
+    noise.get_amplitude_at_frequency_range(0, 8000)
+
+    with pytest.raises(ValueError):
+        noise.get_amplitude_at_frequency_range(0, 16000)

library/tests/test_setup.py

@@ -5,6 +5,19 @@ def test_gas_setup(GPIO, smbus):
     gas.setup()
 
 
+def test_gas_unavailable(GPIO, mocksmbus):
+    from enviroplus import gas
+    mocksmbus.SMBus(1).read_i2c_block_data.side_effect = IOError("Oh noes!")
+    gas._is_setup = False
+    assert gas.available() == False
+
+
+def test_gas_available(GPIO, mocksmbus):
+    from enviroplus import gas
+    gas._is_setup = False
+    assert gas.available() == True
+
+
 def test_gas_read_all(GPIO, smbus):
     from enviroplus import gas
     gas._is_setup = False