testHX711_esp32.ino

#include <Arduino.h>
#include "HX711.h"
#include <Preferences.h>

// HX711 circuit wiring
#define LOADCELL_DOUT_PIN 27
#define LOADCELL_SCK_PIN 26

HX711 scale;
Preferences preferences;

float calibration_factor = 1.0;
const int num_samples = 3;
float known_weights[num_samples];
long raw_readings[num_samples];

void waitForUserInput(const char* prompt, float* value) {
  Serial.println(prompt);
  while (Serial.available()) Serial.read(); // clear buffer
  while (true) {
    if (Serial.available()) {
      String input = Serial.readStringUntil('\n');
      input.trim();
      *value = input.toFloat();
      if (*value > 0) break;
      Serial.println("Invalid input. Please enter a positive number:");
    }
    delay(100);
  }
}

void waitForUserConfirm(const char* prompt) {
  Serial.println(prompt);
  Serial.println("Type 'y' and press Enter to continue...");
  while (Serial.available()) Serial.read(); // clear buffer
  while (true) {
    if (Serial.available()) {
      String input = Serial.readStringUntil('\n');
      input.trim();
      if (input.equalsIgnoreCase("y")) break;
      Serial.println("Please type 'y' and press Enter to confirm.");
    }
    delay(100);
  }
}

void setup() {
  Serial.begin(115200);
  while (!Serial) delay(10);
  scale.begin(LOADCELL_DOUT_PIN, LOADCELL_SCK_PIN);
  preferences.begin("hx711", false);

  float calib = preferences.getFloat("calib", 0.0);
  Serial.print("[DEBUG] Read calibration factor from preferences: ");
  Serial.println(calib, 6);
  bool hasCalib = calib != 0.0 && !isnan(calib);

  if (hasCalib) {
    Serial.print("Found calibration factor in preferences: ");
    Serial.println(calib, 6);
    Serial.println("Type 'y' and press Enter to recalibrate, 's' to show raw data, or any other key to skip calibration.");
    while (Serial.available()) Serial.read(); // clear buffer
    bool doCalib = false;
    while (true) {
      if (Serial.available()) {
        String input = Serial.readStringUntil('\n');
        input.trim();
        if (input.equalsIgnoreCase("y")) {
          doCalib = true;
          break;
        } else if (input.equalsIgnoreCase("s")) {
          Serial.println("\n--- RAW LOADCELL DATA MODE ---");
          Serial.println("Press any key to exit raw data mode.");
          while (true) {
            if (Serial.available()) {
              Serial.readStringUntil('\n');
              break;
            }
            long raw = scale.read();
            Serial.print("Raw: ");
            Serial.println(raw);
            delay(500);
          }
          Serial.println("Exiting raw data mode.\n");
          Serial.println("Type 'y' and press Enter to recalibrate, or any other key to skip calibration.");
          while (Serial.available()) Serial.read(); // clear buffer
          continue;
        } else {
          break;
        }
      }
      delay(100);
    }
    if (!doCalib) {
      Serial.println("Skipping calibration. Using saved calibration factor.");
      preferences.end();
      waitForUserConfirm("Remove all weight from scale. Ready to tare?");
      scale.tare();
      Serial.println("Tare done.");
      return;
    }
    Serial.println("Proceeding with calibration...");
  } else {
    Serial.println("No calibration factor found. Calibration is required.");
    Serial.println("Type 's' and press Enter to show raw data for loadcell test, or any other key to continue.");
    while (Serial.available()) Serial.read(); // clear buffer
    bool showRaw = false;
    while (true) {
      if (Serial.available()) {
        String input = Serial.readStringUntil('\n');
        input.trim();
        if (input.equalsIgnoreCase("s")) showRaw = true;
        break;
      }
      delay(100);
    }
    if (showRaw) {
      Serial.println("\n--- RAW LOADCELL DATA MODE ---");
      Serial.println("Press any key to exit raw data mode.");
      while (true) {
        if (Serial.available()) {
          Serial.readStringUntil('\n');
          break;
        }
        long raw = scale.read();
        Serial.print("Raw: ");
        Serial.println(raw);
        delay(500);
      }
      Serial.println("Exiting raw data mode.\n");
    }
  }

  Serial.println("HX711 scale calibration");

  waitForUserConfirm("Remove all weight from scale. Ready to tare?");
  scale.tare();
  Serial.println("Tare done.");

  for (int i = 0; i < num_samples; i++) {
    Serial.print("\nPlace known weight sample #");
    Serial.print(i + 1);
    Serial.println(" on the scale.");
    waitForUserConfirm("When ready, confirm to take measurement.");
    raw_readings[i] = scale.get_units(15); // filtered average
    Serial.print("Raw reading: ");
    Serial.println(raw_readings[i]);
    waitForUserInput("Enter the actual weight in grams:", &known_weights[i]);
    Serial.print("Recorded: ");
    Serial.print(known_weights[i]);
    Serial.println(" g");
    waitForUserConfirm("Remove the weight and confirm to continue to next sample.");
  }

  // Calculate calibration factor (average of all samples)
  float sum_factor = 0;
  for (int i = 0; i < num_samples; i++) {
    if (known_weights[i] > 0) {
      sum_factor += (float)raw_readings[i] / known_weights[i];
    }
  }
  calibration_factor = sum_factor / num_samples;
  Serial.print("\nCalibration factor calculated: ");
  Serial.println(calibration_factor, 6);

  waitForUserConfirm("Save calibration factor to preferences?");
  bool ok = preferences.putFloat("calib", calibration_factor);
  Serial.print("[DEBUG] preferences.putFloat returned: ");
  Serial.println(ok ? "true" : "false");
  preferences.end(); // Ensure preferences are saved and closed
  Serial.print("[DEBUG] Saved calibration factor: ");
  Serial.println(calibration_factor, 6);
  Serial.println("Calibration factor saved to preferences.");
  Serial.println("Restart the device to use the calibrated scale.");
}

void loop() {
  // After calibration, you can use the calibration factor as follows:
  preferences.begin("hx711", false); // open in read/write mode for compatibility
  float calib = preferences.getFloat("calib", 1.0);
  Serial.print("[DEBUG] loop() read calibration factor: ");
  Serial.println(calib, 6);
  preferences.end();
  float calib_abs = fabs(calib);
  scale.set_scale(calib_abs);
  float weight = scale.get_units(10);
  if (calib < 0) weight = -weight;
  Serial.print("Weight: ");
  Serial.print(weight, 2);
  Serial.println(" g");
  delay(1000);
}