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Merge pull request #2213 from adafruit/food_scale
adding code for the food scale learn guide
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‎NAU7802_Food_Scale/callibration.py‎

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# SPDX-FileCopyrightText: 2022 Liz Clark for Adafruit Industries
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# SPDX-License-Identifier: MIT
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callibration = {
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'offset_val' : 60.8006, # default offset for 6 lbs
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'weight' : 2721.55 # 6 lbs in grams
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}

‎NAU7802_Food_Scale/code.py‎

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# SPDX-FileCopyrightText: 2022 Liz Clark for Adafruit Industries
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# SPDX-License-Identifier: MIT
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import time
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import board
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from digitalio import DigitalInOut, Direction, Pull
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from adafruit_ht16k33.segments import Seg14x4
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from cedargrove_nau7802 import NAU7802
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from callibration import callibration
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# I2C setup with STEMMA port
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i2c = board.STEMMA_I2C()
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# alphanumeric segment displpay setup
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# using two displays together
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display = Seg14x4(i2c, address=(0x71, 0x70))
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# start-up text
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display.print("*HELLO* ")
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# button LEDs
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blue = DigitalInOut(board.A0)
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blue.direction = Direction.OUTPUT
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green = DigitalInOut(board.A2)
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green.direction = Direction.OUTPUT
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# buttons setup
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blue_btn = DigitalInOut(board.A1)
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blue_btn.direction = Direction.INPUT
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blue_btn.pull = Pull.UP
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green_btn = DigitalInOut(board.A3)
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green_btn.direction = Direction.INPUT
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green_btn.pull = Pull.UP
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# nau7802 setup
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nau7802 = NAU7802(board.STEMMA_I2C(), address=0x2A, active_channels=2)
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nau7802.gain = 128
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enabled = nau7802.enable(True)
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# zeroing function
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def zero_channel():
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"""Initiate internal calibration for current channel; return raw zero
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offset value. Use when scale is started, a new channel is green_btned, or to
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adjust for measurement drift. Remove weight and tare from load cell before
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executing."""
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blue.value = True
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print(
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"channel %1d calibrate.INTERNAL: %5s"
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% (nau7802.channel, nau7802.calibrate("INTERNAL"))
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)
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blue.value = False
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print(
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"channel %1d calibrate.OFFSET: %5s"
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% (nau7802.channel, nau7802.calibrate("OFFSET"))
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)
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blue.value = True
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zero_offset = read_raw_value(100) # Read 100 samples to establish zero offset
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print("...channel %1d zeroed" % nau7802.channel)
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blue.value = False
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return zero_offset
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# read raw value function
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def read_raw_value(samples=100):
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"""Read and average consecutive raw sample values. Return average raw value."""
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sample_sum = 0
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sample_count = samples
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while sample_count > 0:
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if nau7802.available:
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sample_sum = sample_sum + nau7802.read()
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sample_count -= 1
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return int(sample_sum / samples)
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# function for finding the average of an array
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def find_average(num):
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count = 0
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for n in num:
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count = count + n
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average = count / len(num)
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return average
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# callibration function
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def calculateCallibration(array):
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for _ in range(10):
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blue.value = True
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green.value = False
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nau7802.channel = 1
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#value = read_raw_value()
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print("channel %1.0f raw value: %7.0f" % (nau7802.channel, read_raw_value()))
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array.append(read_raw_value())
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blue.value = False
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green.value = True
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time.sleep(1)
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green.value = False
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avg = find_average(array)
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return avg
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# blink LED function
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def blink(led, amount, count):
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for _ in range(count):
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led.value = True
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time.sleep(amount)
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led.value = False
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time.sleep(amount)
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# zeroing on startup
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display.fill(0)
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display.marquee("CLEAR SCALE CLEAR", 0.3, False)
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time.sleep(2)
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display.fill(0)
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display.print("ZEROING")
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time.sleep(3)
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# zeroing each channel
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nau7802.channel = 1
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zero_channel() # Calibrate and zero channel
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nau7802.channel = 2
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zero_channel() # Calibrate and zero channel
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display.fill(0)
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display.print("STARTING")
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# variables and states
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clock = time.monotonic() # time.monotonic() device
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mode = "run"
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mode_names = ["SHOW OZ?", " GRAMS?", " ZERO?", "CALIBRTE", " OFFSET?"]
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#offset_val = callibration['offset_val']
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stage = 0
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weight_avg = 0
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zero_avg = 0
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show_oz = True
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show_grams = False
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zero_out = False
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callibrate_mode = False
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blue_btn_pressed = False
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green_btn_pressed = False
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run_mode = True
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while True:
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# button debouncing
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if blue_btn.value and blue_btn_pressed:
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blue_btn_pressed = False
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if green_btn.value and green_btn_pressed:
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green_btn_pressed = False
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green.value = False
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# default run mode
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# checks NAU7802 every 2 seconds
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if run_mode is True and (time.monotonic() - clock) > 2:
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nau7802.channel = 1
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value = read_raw_value()
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# takes value reading and divides with by the offset value
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# to get the weight in grams
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grams = value / callibration['offset_val']
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# convert grams to ounces
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oz = grams / 28.35
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# display in ounces (default)
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if show_oz is True:
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if oz < 0:
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oz = 0
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display.print(" %0.2f oz" % oz)
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# display in grams
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if show_grams is True:
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if grams < 0:
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grams = 0
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display.print(" %0.2f g" % grams)
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clock = time.monotonic()
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# if you press the change mode button
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if (not green_btn.value and not green_btn_pressed) and run_mode:
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green.value = True
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# disables run mode (stops weighing)
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run_mode = False
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show_oz = False
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show_grams = False
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# mode is set to 0
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mode = 0
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# display shows the mode option
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display.print(mode_names[mode])
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blue.value = True
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green_btn_pressed = True
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# advances through the modes menu
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if (not green_btn.value and not green_btn_pressed) and mode != "run":
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green.value = True
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# counts up to 4 and loops back to 0
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mode = (mode+1) % 5
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# updates display
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display.print(mode_names[mode])
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green_btn_pressed = True
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# if you select show_oz
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if (not blue_btn.value and not blue_btn_pressed) and mode == 0:
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# show_oz is set as the state
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show_oz = True
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blue.value = False
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# goes back to weighing mode
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run_mode = True
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mode = "run"
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blue_btn_pressed = True
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# if you select show_grams
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if (not blue_btn.value and not blue_btn_pressed) and mode == 1:
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# show_grams is set as the state
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show_grams = True
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blue.value = False
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# goes back to weighing mode
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run_mode = True
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mode = "run"
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blue_btn_pressed = True
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# if you select zero_out
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if (not blue_btn.value and not blue_btn_pressed) and mode == 2:
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# zero_out is set as the state
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# can zero out the scale without full recallibration
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zero_out = True
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blue.value = False
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mode = "run"
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blue_btn_pressed = True
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# if you select callibrate_mode
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if (not blue_btn.value and not blue_btn_pressed) and mode == 3:
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# callibrate_mode is set as the state
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# starts up the callibration process
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callibrate_mode = True
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blue.value = False
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mode = "run"
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blue_btn_pressed = True
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# if you select the offset
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if (not blue_btn.value and not blue_btn_pressed) and mode == 4:
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# displays the curren offset value stored in the code
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blue.value = False
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display.fill(0)
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display.print("%0.4f" % callibration['offset_val'])
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time.sleep(5)
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mode = "run"
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# goes back to weighing mode
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run_mode = True
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show_oz = True
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blue_btn_pressed = True
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# if the zero_out state is true
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if zero_out and mode == "run":
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# updates display
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display.fill(0)
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display.print("ZEROING")
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blue.value = False
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# runs zero_channel() function on both channels
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nau7802.channel = 1
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zero_channel()
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nau7802.channel = 2
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zero_channel()
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display.fill(0)
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display.print("ZEROED ")
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zero_out = False
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# goes into weighing mode
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run_mode = True
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show_oz = True
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# the callibration process
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# each step is counted in stage
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# blue button is pressed to advance to the next stage
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if callibrate_mode is True and stage == 0:
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blue_btn_pressed = True
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# clear the scale for zeroing
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display.fill(0)
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display.print("REMOVE ")
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stage = 1
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blue.value = True
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# stage 2
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if (not blue_btn.value and not blue_btn_pressed) and stage == 1:
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blue_btn_pressed = True
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# runs the zero out function
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display.fill(0)
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display.print("ZEROING")
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blue.value = False
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nau7802.channel = 1
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zero_channel()
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nau7802.channel = 2
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zero_channel()
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display.fill(0)
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display.print("ZEROED ")
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stage = 2
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blue.value = True
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# stage 3
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if (not blue_btn.value and not blue_btn_pressed) and stage == 2:
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blue_btn_pressed = True
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blue.value = False
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display.print("STARTING")
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blink(blue, 0.5, 3)
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zero_readings = []
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display.print("AVG ZERO")
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# runs the calculateCallibration function
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# takes 10 raw readings, stores them into an array and gets an average
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zero_avg = calculateCallibration(zero_readings)
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stage = 3
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display.fill(0)
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display.print("DONE")
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blue.value = True
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# stage 4
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if (not blue_btn.value and not blue_btn_pressed) and stage == 3:
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# place the known weight item
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# item's weight matches callibration['weight'] in grams
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blue_btn_pressed = True
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blue.value = False
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display.fill(0)
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display.print("PUT ITEM")
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stage = 4
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blue.value = True
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# stage 5
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if (not blue_btn.value and not blue_btn_pressed) and stage == 4:
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blue_btn_pressed = True
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blue.value = False
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display.fill(0)
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display.print("WEIGHING")
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weight_readings = []
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# weighs the item 10 times, stores the readings in an array & averages them
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weight_avg = calculateCallibration(weight_readings)
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# calculates the new offset value
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callibration['offset_val'] = (weight_avg-zero_avg) / callibration['weight']
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display.marquee("%0.2f - CALLIBRATED " % callibration['offset_val'], 0.5, False)
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stage = 5
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display.fill(0)
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display.print("DONE")
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blue.value = True
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# final stage
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if (not blue_btn.value and not blue_btn_pressed) and stage == 5:
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blue_btn_pressed = True
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callibrate_mode = False
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blue.value = False
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# goes back into weighing mode
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show_oz = True
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run_mode = True
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# resets stage
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stage = 0

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