Documentation

// 4x 50kg Load Cells + HX711 - Arduino Body Scale Example
// DT -> D3, SCK -> D2, VCC -> 5V
// Library: "HX711" by Bogdan Necula (bogde)

#include "HX711.h"

const int DT_PIN = 3;
const int SCK_PIN = 2;

// After calibrating: factor = tared raw reading / known weight in kg
float CALIBRATION_FACTOR = 1.0;

HX711 scale;

void setup() {
  Serial.begin(9600);
  scale.begin(DT_PIN, SCK_PIN);

  Serial.println("Empty the platform... taring in 3 s");
  delay(3000);
  scale.tare(20);
  scale.set_scale(CALIBRATION_FACTOR);
  Serial.println("Ready - step on!");
}

void loop() {
  if (scale.is_ready()) {
    float kg = scale.get_units(10);   // average of 10 samples
    long raw = scale.get_value(10);   // tared raw (for calibration)

    Serial.print("Raw: ");
    Serial.print(raw);
    Serial.print("  |  Weight: ");
    Serial.print(kg, 2);
    Serial.println(" kg");
  }
  delay(500);
}

// 4x 50kg Load Cells + HX711 - ESP32 Example
// DT -> GPIO 16, SCK -> GPIO 4, VCC -> 3V3
// Library: "HX711" by Bogdan Necula

#include "HX711.h"

HX711 scale;
float CALIBRATION_FACTOR = 1.0;   // set after calibrating

void setup() {
  Serial.begin(115200);
  scale.begin(16, 4);               // DT, SCK

  Serial.println("Empty the platform... taring in 3 s");
  delay(3000);
  scale.tare(20);
  scale.set_scale(CALIBRATION_FACTOR);
  Serial.println("Ready - step on!");
}

void loop() {
  if (scale.wait_ready_timeout(1000)) {
    Serial.printf("Weight: %.2f kg\n", scale.get_units(10));
  }
  delay(500);
}

#!/usr/bin/env python3
# 4x 50kg Load Cells + HX711 - Raspberry Pi Example (no library needed)
# DT -> GPIO 5 (pin 29), SCK -> GPIO 6 (pin 31), VCC -> 3.3V (pin 1)

import time
import RPi.GPIO as GPIO

DT, SCK = 5, 6
CALIBRATION_FACTOR = 1.0   # tared raw / known kg

GPIO.setmode(GPIO.BCM)
GPIO.setup(DT, GPIO.IN)
GPIO.setup(SCK, GPIO.OUT, initial=GPIO.LOW)

def read_raw():
    while GPIO.input(DT) == 1:      # wait for data ready
        time.sleep(0.001)
    value = 0
    for _ in range(24):             # 24 data bits
        GPIO.output(SCK, GPIO.HIGH)
        GPIO.output(SCK, GPIO.LOW)
        value = (value << 1) | GPIO.input(DT)
    GPIO.output(SCK, GPIO.HIGH)     # gain 128, channel A
    GPIO.output(SCK, GPIO.LOW)
    if value & 0x800000:
        value -= 1 << 24
    return value

def read_average(n=10):
    return sum(read_raw() for _ in range(n)) / n

print("Empty the platform... taring")
time.sleep(2)
zero = read_average(20)
print("Ready - step on!")

try:
    while True:
        kg = (read_average(10) - zero) / CALIBRATION_FACTOR
        print("Weight: {:.2f} kg".format(kg))
        time.sleep(0.5)
except KeyboardInterrupt:
    print("Stopped by user")
finally:
    GPIO.cleanup()

# 4x 50kg Load Cells + HX711 - Pico MicroPython Example (no library)
# DT -> GP14, SCK -> GP15, VCC -> 3V3(OUT)

from machine import Pin
import time

dt = Pin(14, Pin.IN)
sck = Pin(15, Pin.OUT, value=0)

CALIBRATION_FACTOR = 1.0   # tared raw / known kg

def read_raw():
    while dt.value() == 1:
        time.sleep_ms(1)
    value = 0
    for _ in range(24):
        sck.value(1)
        sck.value(0)
        value = (value << 1) | dt.value()
    sck.value(1)               # gain 128, channel A
    sck.value(0)
    if value & 0x800000:
        value -= 1 << 24
    return value

def read_average(n=10):
    return sum(read_raw() for _ in range(n)) / n

print("Empty the platform... taring")
time.sleep(2)
zero = read_average(20)
print("Ready - step on!")

while True:
    kg = (read_average(10) - zero) / CALIBRATION_FACTOR
    print("Weight: {:.2f} kg".format(kg))
    time.sleep(0.5)