projects / EVA-2020-02-2.git / blame
| Commit | Line | Data |
|---|---|---|
| 4f8716dc PH |
1 | """Read the MICS6812 via an ads1015 ADC""" |
| 2 | ||
| 3 | import ads1015 | |
| 4 | import RPi.GPIO as GPIO | |
| 5 | ||
| 6 | MICS6812_EN_PIN = 24 | |
| 7 | ||
| 8 | ||
| 9 | ads1015.I2C_ADDRESS_DEFAULT = ads1015.I2C_ADDRESS_ALTERNATE | |
| 10 | _is_setup = False | |
| 11 | ||
| 12 | ||
| 13 | class Mics6812Reading(object): | |
| 14 | __slots__ = 'oxidising', 'reducing', 'nh3' | |
| 15 | ||
| 16 | def __init__(self, ox, red, nh3): | |
| 17 | self.oxidising = ox | |
| 18 | self.reducing = red | |
| 19 | self.nh3 = nh3 | |
| 20 | ||
| 21 | def __repr__(self): | |
| 22 | return """Oxidising: {:05.02f} | |
| 23 | Reducing: {:05.02f} | |
| 24 | NH3: {:05.02f} | |
| 25 | """.format(self.oxidising, self.reducing, self.nh3) | |
| 26 | ||
| 27 | __str__ = __repr__ | |
| 28 | ||
| 29 | ||
| 30 | def setup(): | |
| 31 | global adc, _is_setup | |
| 32 | if _is_setup: | |
| 33 | return | |
| 34 | _is_setup = True | |
| 35 | ||
| 36 | adc = ads1015.ADS1015(i2c_addr=0x49) | |
| 37 | adc.set_mode('single') | |
| 38 | adc.set_programmable_gain(6.148) | |
| 39 | adc.set_sample_rate(1600) | |
| 40 | ||
| 41 | GPIO.setwarnings(False) | |
| 42 | GPIO.setmode(GPIO.BCM) | |
| 43 | GPIO.setup(MICS6812_EN_PIN, GPIO.OUT) | |
| 44 | GPIO.output(MICS6812_EN_PIN, 1) | |
| 45 | ||
| 46 | ||
| 47 | def read_all(): | |
| 48 | ox = adc.get_voltage('in0/gnd') | |
| 49 | red = adc.get_voltage('in1/gnd') | |
| 50 | nh3 = adc.get_voltage('in2/gnd') | |
| 51 | ||
| 52 | ox = (ox * 56000) / (3.3 - ox) | |
| 53 | red = (red * 56000) / (3.3 - red) | |
| 54 | nh3 = (nh3 * 56000) / (3.3 - nh3) | |
| 55 | ||
| 56 | return Mics6812Reading(ox, red, nh3) | |
| 57 | ||
| 58 | ||
| 59 | def read_oxidising(): | |
| 60 | """Return gas resistance for oxidising gases. | |
| 61 | ||
| 62 | Eg chlorine, nitrous oxide | |
| 63 | """ | |
| 64 | setup() | |
| 65 | return read_all().oxidising | |
| 66 | ||
| 67 | ||
| 68 | def read_reducing(): | |
| 69 | """Return gas resistance for reducing gases. | |
| 70 | ||
| 71 | Eg hydrogen, carbon monoxide | |
| 72 | """ | |
| 73 | setup() | |
| 74 | return read_all().reducing | |
| 75 | ||
| 76 | ||
| 77 | def read_nh3(): | |
| 78 | """Return gas resistance for nh3/ammonia""" | |
| 79 | setup() | |
| 80 | return read_all().nh3 |