hx711-rpi-py 0.1.0

Python bindings for Raspberry Pi HX711 C++ Library

Raspberry Pi HX711 Python Bindings

Python bindings for Raspberry Pi HX711 C++ Library

• Read from a HX711 using Python
• Use with Raspberry Pi
• Developed and tested with a Raspberry Pi Zero W (should work on other Pis)

Sample Output

The .gif above illustrates the output of a simple Python script on a Raspberry Pi Zero W where the HX711 chip was operating at 80Hz. In this example, each time the .weight function is called the median of three samples was used to calculate the weight in grams.

Examples

SimpleHX711 Example

from HX711 import *

# create a SimpleHX711 object using GPIO pin 2 as the data pin,
# GPIO pin 3 as the clock pin, -370 as the reference unit, and
# -367471 as the offset
hx = SimpleHX711(2, 3, -370, -367471)

# set the scale to output weights in ounces
hx.setUnit(Mass.Unit.OZ)

# constantly output weights using the median of 35 samples
while True:
    print(hx.weight(35))

AdvancedHX711 Example

from HX711 import *
from datetime import timedelta

# create an AdvancedHX711 object using GPIO pin 2 as the data pin,
# GPIO pin 3 as the clock pin, -370 as the reference unit, -367471
# as the offset, and indicate that the chip is operating at 80Hz
hx = AdvancedHX711(2, 3, -370, -367471, Rate.HZ_80)

# constantly output weights using the median of all samples
# obtained within 1 second
while True:
    print(hx.weight(timedelta(seconds=1)))

Build

# Step 1: clone this repository
pi@raspberrypi:~ $ git clone https://github.com/endail/hx711-rpi-py
pi@raspberrypi:~ $ cd hx711-rpi-py

# Step 2: install liblgpio and libhx711 dependencies
pi@raspberrypi:~/hx711-rpi-py $ sudo ./install-deps

# Step 3: build (this may take some time)
pi@raspberrypi:~/hx711-rpi-py $ make

# bin directory will contain python module
# eg. HX711.cpython-37m-arm-linux-gnueabihf.so
# import this file into your Python script as in examples above

Calibrate

There is a Python script in the src directory you can use to calibrate your load cell and obtain the reference unit and offset values referred to above. After you build the Python module as described in the section above, run the script and follow the prompts:

pi@raspberrypi:~/hx711-rpi-py $ python3 src/calibrate.py

Documentation

As the Python code relies upon the underlying C++ library, the documentation is identical. However, not all of the code is exposed to Python. An example is the Utility class, which is only meant for use within the C++ library. You can check precisely which functionality is accessible through Python in the bindings.cpp file.