const int COL1 = 3;     // Col #1
const int LED = 26;     // row 1 led
void setup() {  
  Serial.begin(9600);
  Serial.println("microbit is ready!");
  pinMode(COL1, OUTPUT);
  digitalWrite(COL1, LOW); 
  pinMode(LED, OUTPUT);   
}
void loop(){
  Serial.println("blink!"); 
  digitalWrite(LED, HIGH);
  delay(500);
  digitalWrite(LED, LOW);
  delay(500);
}