Skip to content

Instantly share code, notes, and snippets.

Embed
What would you like to do?
Find weight from scale using python and usb
# -*- coding: utf-8 -*-
"""
scale.py
Utilities to fetch weight from weighing scales
:copyright: (c) 2016-2018 by Fulfil.IO Inc.
:license: see LICENSE for details.
"""
from collections import namedtuple
import hid
from pint import UnitRegistry
UREG = UnitRegistry()
DATA_MODE_GRAMS = 2
DATA_MODE_KILOS = 3
DATA_MODE_OUNCES = 11
DATA_MODE_POUNDS = 12
DATA_STABLE = 4
SCALE_VENDOR_WHITELIST = [
0x6096, # SANFORD
0x0922, # Dymo
0x1446, # WeighMax
0x0eb8, # Mettler Toledo
0x6096, # Pelouze
0x2474, # Stamps.com
0x0b67, # Fairbanks
]
class FulfilException(Exception):
pass
class ScaleReadError(FulfilException):
pass
def get_scale(product_string):
"""
Return the scale_hid with the given product name
"""
try:
scale_data, = filter(
lambda h: h['product_string'] == product_string,
get_scale_hid_devices()
)
except ValueError:
raise ScaleReadError('No scale selected.')
try:
scale_hid = hid.device(
scale_data['vendor_id'],
scale_data['product_id'],
)
scale_hid.open_path(scale_data['path'])
except IOError:
raise ScaleReadError('Error connecting to the scale')
if not scale_hid:
raise ScaleReadError('Error connecting to the scale')
return scale_hid
Weight = namedtuple('Weight', ['weight', 'stable', 'raw_data'])
def get_weight(scale_name=None):
"""
API which reads the weight from weighing scale
:return: A namedtuple
"""
scale_hid = get_scale(scale_name)
# Read from hid scale
raw_data = scale_hid.read(64)
scale_hid.close()
return (
parse_weight(*raw_data[2:]),
raw_data[1] == DATA_STABLE,
raw_data,
)
def parse_weight(unit, factor, weight_part_1, weight_part_2):
"""
Compute and return the weight in multiple UOMs
"""
weight = 0.0
raw_weight = weight_part_1 + (weight_part_2 * 256)
if unit == DATA_MODE_GRAMS:
weight = UREG.g * raw_weight
elif unit == DATA_MODE_KILOS:
weight = UREG.kg * raw_weight
elif unit == DATA_MODE_OUNCES:
weight = UREG.oz * raw_weight * 0.1
elif unit == DATA_MODE_POUNDS:
weight = UREG.lbs * raw_weight * 0.1
return weight
def get_scale_hid_devices():
"""
Return a list of HID devices
"""
devices = []
for device in hid.enumerate():
if device['vendor_id'] in SCALE_VENDOR_WHITELIST:
devices.append(device)
return devices
if __name__ == '__main__':
scales = get_scale_hid_devices()
for scale in scales:
print "Manufacturer:", scale['manufacturer_string']
print "Product:", scale['product_string']
print get_weight(scale['product_string'])
if not scales:
print "No Scales Found"
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
You can’t perform that action at this time.