Arduino--基础（二）--LCD Keypad Shield 的使用

测试代码：

#include 

LiquidCrystal lcd(8, 13, 9, 4, 5, 6, 7);

char msgs[5][16] = {"Right Key OK ",
                    "Up Key OK    ",               
                    "Down Key OK  ",
                    "Left Key OK  ",
                    "Select Key OK" };

int adc_key_val[5] ={50, 200, 400, 600, 800 };
int NUM_KEYS = 5;
int adc_key_in;
int key=-1;
int oldkey=-1;

void setup()
{
  lcd.clear(); 
  lcd.begin(16, 2);
  lcd.setCursor(0,0); 
  lcd.print("ADC key testing"); 
}

void loop()
{
  adc_key_in = analogRead(0);    // read the value from the sensor 
  key = get_key(adc_key_in);  // convert into key press

  if (key != oldkey)   // if keypress is detected
   {
    delay(50);  // wait for debounce time
    adc_key_in = analogRead(0);    // read the value from the sensor 
    key = get_key(adc_key_in);    // convert into key press
    if (key != oldkey)    
    {   
      lcd.setCursor(0, 1);
      oldkey = key;
      if (key >=0){
           lcd.print(msgs[key]);              
      }
    }
  }
 delay(100);
}

// Convert ADC value to key number
int get_key(unsigned int input)
{
    int k;

    for (k = 0; k < NUM_KEYS; k++)
    {
      if (input < adc_key_val[k])
 {
            return k;
        }
   }

    if (k >= NUM_KEYS)k = -1;  // No valid key pressed
    return k;
}