gistfile1.txt

int gpio0 = 21;
int enable = 23;

enum {uart, flash} mode = flash;

void setup() {  
  Serial.begin(115200);

  if(mode == flash){
    Serial1.begin(76800);
  }
  else if(mode == uart){
    Serial1.begin(115200);
  }
    
  pinMode(gpio0, OUTPUT);
  pinMode(enable, OUTPUT);

  if(mode == flash){
    digitalWrite(gpio0, HIGH);  
  }
  else if(mode == uart){
    digitalWrite(gpio0, LOW);
  }
  
  digitalWrite(enable, LOW);
  Serial.println("GPIO=HIGH, ENABLE=LOW");
  
  delay(100);
  
  digitalWrite(enable, HIGH);
  Serial.println("GPIO=HIGH, ENABLE=HIGH");

  if(mode == flash){
    delay(1000);
    Serial1.begin(115200);
  }
}

void loop() {
  if(Serial1.available()){
    Serial.write(Serial1.read());
  }

  if(Serial.available()){
    Serial1.write(Serial.read());
  }
}