• MCU: ESP32 development board / ESP32-DEVKITC-compatible
• Framework: Arduino
• Build system: PlatformIO
• Firmware roles: U1 = sensor node, U2 = optional UART receiver

Ini
[platformio]
default_envs = esp32_u1_sensor

[env]
platform = espressif32
board = esp32dev
framework = arduino
monitor_speed = 115200
lib_deps =
    bogde/HX711@^0.7.5
    adafruit/Adafruit MPU6050@^2.2.6
    adafruit/Adafruit Unified Sensor@^1.1.14
    paulstoffregen/OneWire@^2.3.8
    milesburton/DallasTemperature@^3.11.0

[env:esp32_u1_sensor]
build_flags = -DDEVICE_U1_SENSOR

[env:esp32_u2_receiver]
build_flags = -DDEVICE_U2_RECEIVER

Cpp
#include <Arduino.h>
#include <Wire.h>
#include <HX711.h>
#include <Adafruit_MPU6050.h>
#include <Adafruit_Sensor.h>
#include <OneWire.h>
#include <DallasTemperature.h>

#define I2C_SDA_PIN          21
#define I2C_SCL_PIN          22
#define HX711_DOUT_PIN       32
#define HX711_SCK_PIN        33
#define DS18B20_DQ_PIN        4
#define ESP32_LINK_TX_PIN    25
#define ESP32_LINK_RX_PIN    26

#define SENSOR_INTERVAL_MS 1000UL
#define LINK_BAUD          115200
#define DEBUG_BAUD         115200

HardwareSerial LinkSerial(2);

#ifdef DEVICE_U1_SENSOR
HX711 scale;
Adafruit_MPU6050 mpu;
OneWire oneWire(DS18B20_DQ_PIN);
DallasTemperature ds18b20(&oneWire);
unsigned long lastReadMs = 0;

float readLoadCellRaw() {
  if (scale.is_ready()) {
    return (float)scale.read_average(5);
  }
  Serial.println("HX711 not ready");
  return NAN;
}

bool readMpu(float &ax, float &ay, float &az, float &gx, float &gy, float &gz, float &tempC) {
  sensors_event_t accel, gyro, temp;
  if (!mpu.getEvent(&accel, &gyro, &temp)) {
    return false;
  }
  ax = accel.acceleration.x;
  ay = accel.acceleration.y;
  az = accel.acceleration.z;
  gx = gyro.gyro.x;
  gy = gyro.gyro.y;
  gz = gyro.gyro.z;
  tempC = temp.temperature;
  return true;
}

float readDs18b20C() {
  ds18b20.requestTemperatures();
  float t = ds18b20.getTempCByIndex(0);
  if (t == DEVICE_DISCONNECTED_C) {
    Serial.println("DS18B20 disconnected");
    return NAN;
  }
  return t;
}

void setupU1() {
  Serial.begin(DEBUG_BAUD);
  delay(300);
  Serial.println("U1 sensor node starting");

  LinkSerial.begin(LINK_BAUD, SERIAL_8N1, ESP32_LINK_RX_PIN, ESP32_LINK_TX_PIN);

  Wire.begin(I2C_SDA_PIN, I2C_SCL_PIN);
  if (!mpu.begin(0x68, &Wire)) {
    Serial.println("MPU6050 not found at 0x68; check wiring/pull-ups");
  } else {
    mpu.setAccelerometerRange(MPU6050_RANGE_8_G);
    mpu.setGyroRange(MPU6050_RANGE_500_DEG);
    mpu.setFilterBandwidth(MPU6050_BAND_21_HZ);
    Serial.println("MPU6050 initialized");
  }

  scale.begin(HX711_DOUT_PIN, HX711_SCK_PIN);
  scale.set_scale();
  scale.tare(10);

  ds18b20.begin();
  Serial.println("Init complete");
}

void loopU1() {
  unsigned long now = millis();
  if (now - lastReadMs < SENSOR_INTERVAL_MS) return;
  lastReadMs = now;

  float loadRaw = readLoadCellRaw();
  float ax = NAN, ay = NAN, az = NAN, gx = NAN, gy = NAN, gz = NAN, mpuTemp = NAN;
  bool mpuOk = readMpu(ax, ay, az, gx, gy, gz, mpuTemp);
  float surfaceTemp = readDs18b20C();

  String msg = "{\"load_raw\":" + String(loadRaw, 0) +
               ",\"mpu_ok\":" + String(mpuOk ? 1 : 0) +
               ",\"ax\":" + String(ax, 3) +
               ",\"ay\":" + String(ay, 3) +
               ",\"az\":" + String(az, 3) +
               ",\"gx\":" + String(gx, 3) +
               ",\"gy\":" + String(gy, 3) +
               ",\"gz\":" + String(gz, 3) +
               ",\"surface_temp_c\":" + String(surfaceTemp, 2) + "}";

  Serial.println(msg);
  LinkSerial.println(msg);
}
#endif

#ifdef DEVICE_U2_RECEIVER
void setupU2() {
  Serial.begin(DEBUG_BAUD);
  delay(300);
  Serial.println("U2 receiver starting");
  LinkSerial.begin(LINK_BAUD, SERIAL_8N1, ESP32_LINK_RX_PIN, ESP32_LINK_TX_PIN);
}

void loopU2() {
  while (LinkSerial.available()) {
    String line = LinkSerial.readStringUntil('\n');
    line.trim();
    if (line.length() > 0) {
      Serial.print("From U1: ");
      Serial.println(line);
    }
  }
}
#endif

void setup() {
#ifdef DEVICE_U1_SENSOR
  setupU1();
#elif defined(DEVICE_U2_RECEIVER)
  setupU2();
#else
  Serial.begin(DEBUG_BAUD);
  Serial.println("Define DEVICE_U1_SENSOR or DEVICE_U2_RECEIVER in build_flags");
#endif
}

void loop() {
#ifdef DEVICE_U1_SENSOR
  loopU1();
#elif defined(DEVICE_U2_RECEIVER)
  loopU2();
#else
  delay(1000);
#endif
}

Bash
pio run -e esp32_u1_sensor
pio run -e esp32_u1_sensor -t upload
pio device monitor -b 115200

pio run -e esp32_u2_receiver
pio run -e esp32_u2_receiver -t upload
pio device monitor -b 115200