def get_water_level(cls):
""" This method uses the ADC on the control module to measure
the current water tank level and returns the water volume
remaining in the tank.
For this method, it is assumed that a simple voltage divider
is used to interface the sensor to the ADC module.
Testing shows that the sensor response is not completely linear,
though it is quite close. To make the results more accurate,
a mapping method approximated by a linear fit to data is used.
"""
# ----------
# These values should be updated based on the real system parameters
vref = 4.95
tank_height = 17.5 # in centimeters (height of container)
rref = 2668 # Reference resistor
# ----------
val = 0
for i in range(5):
# Take five readings and do an average
# Fetch value from ADC (0x69 - ch1)
val = get_ADC_value(cls.bus, 0x6c, 1) + val
avg = val / 5
water_sensor_res = rref * avg/(vref - avg)
depth_cm = water_sensor_res * \
(-.0163) + 28.127 # measured transfer adjusted offset
if depth_cm < 1.0: # Below 1cm, the values should not be trusted.
depth_cm = 0
cls.water_remaining = depth_cm / tank_height
# Return the current depth in case the user is interested in
# that parameter alone. (IE for automatic shut-off)
return depth_cm/tank_height
def update_soil_moisture(self):
""" Method will select the ADC module,
turn on the analog sensor, wait for voltage settle,
and then digitize the sensor voltage.
Voltage division/signal loss is accounted for by
scaling up the sensor output.
This may need to be adjusted if a different sensor is used
"""
SensorCluster.analog_sensor_power(SensorCluster.bus, "on") # turn on sensor
sleep(.2)
TCA_select(SensorCluster.bus, self.mux_addr, SensorCluster.adc_chan)
moisture = get_ADC_value(
SensorCluster.bus, SensorCluster.adc_addr, SensorCluster.moisture_chan)
status = TCA_select(SensorCluster.bus, self.mux_addr, "off") # Turn off mux.
SensorCluster.analog_sensor_power(SensorCluster.bus, "off") # turn off sensor
if (moisture >= 0):
soil_moisture = moisture/2.048 # Scale to a percentage value
self.soil_moisture = round(soil_moisture,3)
else:
raise SensorError(
"The soil moisture meter is not configured correctly.")
return status