一、设备预期功能 #

• 检测环境温度，实时显示当前温度与设定温度
• 通过高/低按钮调整设定温度值
• 当实际温度高于设定值时，自动启动风扇，同时扬声器触发一次提示音

二、故障现象 #

代码编译运行无报错，扬声器、温度传感器（TMP）、风扇电机（MOTOR）均工作正常，但LCD显示屏无任何显示

三、设备运行代码 #

#include <Wire.h>
#define TEMP_ADDR 72
#include <LiquidCrystal.h>

LiquidCrystal lcd(2, 3, 4, 5, 6, 7);

byte degree[8] = {
  B00110,
  B01001,
  B01001,
  B00110,
  B00000,
  B00000,
  B00000,
  B00000,
};

byte fan_on[8] = {
  B00100,
  B10101,
  B01110,
  B11111,
  B01110,
  B10101,
  B00100,
  B00000,
};

byte fan_off[8] = {
  B00100,
  B00100,
  B00100,
  B11111,
  B00100,
  B00100,
  B00100,
  B00000,
};

const int SPEAKER=8;
const int DOWN_BUTTON =9;
const int UP_BUTTON=10;
const int FAN =11;
const int T0=0;

boolean lastDownTempButton = LOW;
boolean currentDownTempButton = LOW;
boolean lastUpTempButton = LOW;
boolean currentUpTempButton = LOW;

int set_temp = 23;
boolean one_time = false;

void setup() {
  pinMode(FAN, OUTPUT);
  //Create a wire object for the temp sensor
  Wire.begin();
  //Set up the LCD's number of columns and rows
  lcd.begin(16, 2);
  //Make custom characters
  lcd.createChar(0, degree);
  lcd.createChar(1, fan_off);
  lcd.createChar(2, fan_on);
  //Print a static message to the LCD
  lcd.setCursor(0,0);
  lcd.print("Current:");
  lcd.setCursor(10,0);
  lcd.write((byte)0);
  lcd.setCursor(11,0);
  lcd.print("C");
  lcd.setCursor(0,1);
  lcd.print("Set:");
  lcd.setCursor(10,1);
  lcd.write((byte)0);
  lcd.setCursor(11,1);
  lcd.print("C");
  lcd.setCursor(15,1);
  lcd.write(1);
}

boolean debounce(boolean last, int pin) {
  boolean current = digitalRead(pin);
  if (last != current) {
    delay(5);
    current = digitalRead(pin);
  }
  return current;
}

void loop() {
  /* 
  Wire.beginTransmission(TEMP_ADDR);
  Wire.write(0);
  Wire.endTransmission();
  Wire.requestFrom(TEMP_ADDR, 1);
  while(Wire.available() == 0);
  int c = Wire.read(); 
  */
  // for LM35 temperature sensor (Chapter3. 아날로그 신호와 센서값)
  int c = analogRead(T0);
  c = c*5.0 /1024.0 * 100;
  Serial.println(c);

  lcd.setCursor(8,0); //Move the cursor
  lcd.print(c); //Print this new value
  lcd.setCursor(8,0);
  lcd.print(c);

  currentDownTempButton = debounce(lastDownTempButton, DOWN_BUTTON);
  currentUpTempButton = debounce(lastUpTempButton, UP_BUTTON);

  if (lastDownTempButton== LOW && currentDownTempButton == HIGH) {
    set_temp--;
  }
  //Turn up the set temp
  else if (lastUpTempButton== LOW && currentUpTempButton == HIGH) {
    set_temp++;
  }

  //Print the set temp
  lcd.setCursor(8,1);
  lcd.print(set_temp);

  lastDownTempButton = currentDownTempButton;
  lastUpTempButton = currentUpTempButton;

  if (c >= set_temp) {
    if (!one_time) {
      tone(SPEAKER, 400);
      delay(500);
      one_time = true;
    } else {
      noTone(SPEAKER);
    }
    digitalWrite(FAN, HIGH);
    lcd.setCursor(15,1);
    lcd.write(2);
  } else {
    noTone(SPEAKER);
    one_time = false;
    digitalWrite(FAN, LOW);
    lcd.setCursor(15,1);
    lcd.write(1);
  }
}

针对性排查建议 #

既然其他模块都正常工作，问题大概率集中在LCD的硬件连接或初始化环节，你可以按以下步骤排查：

1. 核对LCD接线：确认LiquidCrystal lcd(2, 3, 4, 5, 6, 7)里的引脚是否和实际硬件的RS、EN、D4-D7引脚一一对应，别接错顺序
2. 检查电源与对比度：确保LCD的VCC接5V、GND接地，同时调节对比度电位器（如果有）——电位器拧到极端会导致屏幕全黑
3. 简化测试LCD：暂时注释掉自定义字符和动态显示代码，只保留lcd.begin(16,2)和lcd.print("LCD Test")，看屏幕是否能显示基础文本，快速区分是代码逻辑还是硬件问题
4. 调整初始化顺序：尝试把lcd.begin(16,2)移到Wire.begin()之前执行，排除I2C总线对LCD初始化的干扰

内容的提问来源于stack exchange，提问作者Regina Kang