# SPDX-FileCopyrightText: 2022 Liz Clark for Adafruit Industries # SPDX-License-Identifier: MIT import time import board import simpleio import adafruit_bmp280 import pwmio import displayio from adafruit_motor import servo import terminalio from adafruit_clue import clue from adafruit_display_text import label # pwm setup for servo pwm = pwmio.PWMOut(board.D0, duty_cycle=2 ** 15, frequency=50) gauge = servo.Servo(pwm) # bmp280 sensor setup i2c = board.I2C() # uses board.SCL and board.SDA # i2c = board.STEMMA_I2C() # For using the built-in STEMMA QT connector on a microcontroller bmp280 = adafruit_bmp280.Adafruit_BMP280_I2C(i2c) # change depending on your location's elevation NOMINAL_PRESSURE = 1005.94 PRESSURE_RANGE = 40 # hPa, expected pressure range variance caused by local weather PRESSURE_LOW_LIM = NOMINAL_PRESSURE - PRESSURE_RANGE PRESSURE_HIGH_LIM = NOMINAL_PRESSURE + PRESSURE_RANGE # board display # scaling for terminalio font display = board.DISPLAY group = displayio.Group(scale=3) # text elements temp_header = "Temperature:" press_header = "Pressure:" temp_text = " ºC" press_text = " hPa" font = terminalio.FONT blue = 0x0000FF red = 0xFF0000 # temperature text elements temp_label = label.Label(font, text=temp_header, color=red, x=5, y=10) temp_data = label.Label(font, text=temp_text, color=red, x=5, y=25) # pressure text elements press_label = label.Label(font, text=press_header, color=blue, x=5, y=50) press_data = label.Label(font, text=press_text, color=blue, x=5, y=65) # adding text to display group group.append(temp_label) group.append(press_label) group.append(temp_data) group.append(press_data) display.root_group = group # function to convert celcius to fahrenheit def c_to_f(temp): temp_f = (temp * 9/5) + 32 return temp_f # function to convert hPa to inHg def hpa_to_inHg(hPa): inches_mercury = hPa * 0.02953 return inches_mercury # time.monotonic clock clock = 0 # units state metric_units = False while True: # non-blocking 2 second delay if (clock + 2) < time.monotonic(): # map servo range to barometric pressure range servo_value = simpleio.map_range(bmp280.pressure, PRESSURE_LOW_LIM, PRESSURE_HIGH_LIM, 180, 0) # set servo to pressure gauge.angle = servo_value # print data for debugging print("\nTemperature: %0.1f C" % bmp280.temperature) print("Pressure: %0.1f hPa" % bmp280.pressure) print(servo_value) # if metric units... if metric_units: # update temp & pressure text in celcius and hPa temp_data.text = "%0.1f ºC" % bmp280.temperature press_data.text = "%0.1f hPa" % bmp280.pressure # if imperial units... else: # convert celcius to fahrenheit temp_fahrenheit = c_to_f(bmp280.temperature) # convert hPa to inHg pressure_inHg = hpa_to_inHg(bmp280.pressure) # update temp & pressure text temp_data.text = "%0.1f ºF" % temp_fahrenheit press_data.text = "%0.1f inHg" % pressure_inHg # reset time.monotonic() clock clock = time.monotonic() # if a button is pressed, metric_units is True, show metric if clue.button_a: metric_units = True # if b button is pressed, metric_units is False, show imperial units if clue.button_b: metric_units = False
The code begins by creating a displayio
group and some text elements to show on the CLUE display.
# board display # scaling for terminalio font display = board.DISPLAY group = displayio.Group(scale=3) # text elements temp_header = "Temperature:" press_header = "Pressure:" temp_text = " ºC" press_text = " hPa" font = terminalio.FONT blue = 0x0000FF red = 0xFF0000
Then, the servo object is created with PWM and the BMP280 sensor is instantiated over I2C.
# pwm setup for servo pwm = pwmio.PWMOut(board.D0, duty_cycle=2 ** 15, frequency=50) gauge = servo.Servo(pwm) # bmp280 sensor setup i2c = board.I2C() # uses board.SCL and board.SDA bmp280 = adafruit_bmp280.Adafruit_BMP280_I2C(i2c)
Nominal Baseline Pressure
The deviation from the nominal baseline pressure is used to show your current weather conditions with the servo. The NOMINAL_PRESSURE
value must be set for your location (covered later in guide on the Usage page). The PRESSURE_RANGE
value can be adjusted as needed for typical local weather driven deviations. A lower value will make the detection more sensitive.
# change depending on your location's elevation NOMINAL_PRESSURE = 1005.94 PRESSURE_RANGE = 40 # hPa, expected pressure range variance caused by local weather PRESSURE_LOW_LIM = NOMINAL_PRESSURE - PRESSURE_RANGE PRESSURE_HIGH_LIM = NOMINAL_PRESSURE + PRESSURE_RANGE
There are four text labels that are shown on the display. temp_label
and press_label
are headers with the text "Temperature:"
and "Pressure:"
. temp_data
and press_data
are updated in the loop to show the readings from the BMP280 sensor.
# temperature text elements temp_label = label.Label(font, text=temp_header, color=red, x=5, y=10) temp_data = label.Label(font, text=temp_text, color=red, x=5, y=25) # pressure text elements press_label = label.Label(font, text=press_header, color=blue, x=5, y=50) press_data = label.Label(font, text=press_text, color=blue, x=5, y=65) # adding text to display group group.append(temp_label) group.append(press_label) group.append(temp_data) group.append(press_data) display.root_group = group
There are two functions to convert metric units to imperial units. c_to_f()
converts Celsius to Fahrenheit by passing the temperature in Celsius and returning the temperature in Fahrenheit.
hpa_to_inHg()
converts hectopascals to inches of mercury by passing the barometric pressure in hectopascals and returning the pressure reading in inches of mercury.
Two variables are declared before the loop. clock
is a time.monotonic()
device and metric_units
is used to determine which units are being shown on the display and is affected by the CLUE buttons.
# function to convert celcius to fahrenheit def c_to_f(temp): temp_f = (temp * 9/5) + 32 return temp_f # function to convert hPa to inHg def hpa_to_inHg(hPa): inches_mercury = hPa * 0.02953 return inches_mercury # time.monotonic clock clock = time.monotonic() # units state metric_units = True
In the loop, the BMP280 pressure reading is mapped from the calculated pressure range with your nominal baseline pressure to the value range of the servo motor angle. The servo motor angle is then set to that mapped value.
# non-blocking 2 second delay if (clock + 2) < time.monotonic(): # map servo range to barometric pressure range servo_value = simpleio.map_range(bmp280.pressure, PRESSURE_LOW_LIM, PRESSURE_HIGH_LIM, 180, 0) # set servo to pressure gauge.angle = servo_value
If metric_units
is True
, then the temperature and air pressure readings are displayed on the CLUE in Celsius and hPa.
# if metric units... if metric_units: # update temp & pressure text in celcius and hPa temp_data.text = "%0.1f ºC" % bmp280.temperature press_data.text = "%0.1f hPa" % bmp280.pressure
If metric_units
is False
, the readings from the BMP280 are converted to imperial units with the two conversion functions and are shown on the display in Fahrenheit and inHg.
# if imperial units... else: # convert celcius to fahrenheit temp_fahrenheit = c_to_f(bmp280.temperature) # convert hPa to inHg pressure_inHg = hpa_to_inHg(bmp280.pressure) # update temp & pressure text temp_data.text = "%0.1f ºF" % temp_fahrenheit press_data.text = "%0.1f inHg" % pressure_inHg
If CLUE button A is pressed, then the BMP280 readings are displayed in metric units. If the CLUE button B is pressed, then the BMP280 readings are displayed in imperial units.
# if a button is pressed, metric_units is True, show metric if clue.button_a: metric_units = True # if b button is pressed, metric_units is False, show imperial units if clue.button_b: metric_units = False