loadcell.py

import time
import board
from cedargrove_nau7802 import NAU7802

nau7802 = NAU7802(board.I2C(), address=0x2A, active_channels=1)


def zero_channel():
    """Initiate internal calibration for current channel.Use when scale is started,
    a new channel is selected, or to adjust for measurement drift. Remove weight
    and tare from load cell before executing."""
    print(
        "channel %1d calibrate.INTERNAL: %5s"
        % (nau7802.channel, nau7802.calibrate("INTERNAL"))
    )
    print(
        "channel %1d calibrate.OFFSET:   %5s"
        % (nau7802.channel, nau7802.calibrate("OFFSET"))
    )
    print("...channel %1d zeroed" % nau7802.channel)


def read_raw_value(samples=1):
    """Read and average consecutive raw sample values. Return average raw value."""
    sample_sum = 0
    while not nau7802.available():
        pass
    sample_sum = nau7802.read()
    return int(sample_sum)

constant = 384 / 34726


# Instantiate and calibrate load cell inputs
print("*** Instantiate and calibrate load cells")
# Enable NAU7802 digital and analog power
enabled = nau7802.enable(True)
print("Digital and analog power enabled:", enabled)

print("REMOVE WEIGHTS FROM LOAD CELLS")
time.sleep(3)

nau7802.channel = 1
zero_channel()  # Calibrate and zero channel

print("READY")

### Main loop: Read load cells and display raw values
current_time = 0; prev_time = 0;
while True:
    print("=====")
    nau7802.channel = 1
    prev_time = time.time() * 1000
    value = read_raw_value()
    #print(nau7802.channel, value*constant)
    current_time = time.time() * 1000
    print(current_time - prev_time)
    #print("channel %1.0f raw value: %7.0f" % (nau7802.channel, value))
    time.sleep(0.01)