Arduino Nano communication problem

Using Arduino IDE 1.x
1

Hello everyone, as I'm new here. I'm not very experienced so please be patient if answer to my question is trivial, however I cannot find it myself, even though I have tried hard.
I have a problem with my Arduino Nano 328P (a clone actually, marked as "Deek-Robot NANO V4.0"). I have created a sketch and succesfully uploaded it, but the problem appeared when I tried to update it - during upload Arduino IDE either says that COM port is already in use (if I connect Arduino after starting IDE) or Java process crashes (if it is connected before starting IDE). I'm sure that this is because I messed with RX, TX pins. In my project I need all possible digital pins and I had to use also D0 and D1. THe relevant part of my code is:

void setup(){
  pinMode(2, OUTPUT);
  pinMode(3, OUTPUT);
  pinMode(4, OUTPUT);
  pinMode(5, OUTPUT);
  pinMode(6, OUTPUT);
  pinMode(7, OUTPUT);

  pinMode(8, OUTPUT);
  pinMode(9, OUTPUT);
  pinMode(10, OUTPUT);
  pinMode(11, OUTPUT);
  pinMode(12, OUTPUT);
  pinMode(13, OUTPUT);

  delay(300);

  pinMode(A0, OUTPUT);
  pinMode(A1, OUTPUT);
  pinMode(A2, OUTPUT);
  pinMode(A3, INPUT);
  pinMode(0, OUTPUT);
  pinMode(1, OUTPUT);
  pinMode(A5, OUTPUT);
  pinMode(A4, INPUT);

// here some reading from pins A3 and A4, and writing to A0, A1, A2, A5, 0 and 1
}

Did I disabled possibility to program Arduino through USB? What are my options now? Please post some answers or direct me to a tutorial if there is any.

2

you can use analog input pins as digital by the statement pinMode(Ax, OUTPUT); (Ax is A0,A1,...). Then free up the RX and TX pins for upload and communication.

3

You can use as written - to download: press & hold the reset button, when the IDE shows "compiled xxx of 32xxx bytes" release the reset. Might take a few tries to get the timing right. Also easier if you do File:Preferences and turn on Verbose outputs.
The reset makes sure the bootloader is ready for the downloa and that the sketch hasn't started already to interfere on the serial lines.

4

@groundfungus
As you can see in my sketch, I'm already using analog pins as digital outputs, and even though it's not enough. Using a shift register is not an option too, beacause I need ability to switch outputs with frequency up to 1 MHz, so I won't have time to transmit data serially. Besides, my problem is not the code, but the fact that I don't have access to my Arduino.

@CrossRoads
I tried that already, but it seems that the key is timing. I'll try your advice and turn verbose output on. Thanks!
Also, for the future - what should I do to avoid such situation? As you can see, I've put 300ms delay, but it is clearly not enough.

5

Well, you can 'not' use the serial pins as outputs.
The bootloader takes a few seconds, so 300mS is not long enough.

6

OK, problem solved. I aquired USBasp programmer and reburned bootloader. After few experiments (and few sequential reburns) I found out, that 1800 ms delay on startup allows to use D0 and D1 as outputs without blocking ability to reprogram normally through USB.

7

One more question. If I want to restore USB programming ability - is it enough to just add:

  pinMode(0, INPUT);

I want to remove 2s pause at the start, but want to enable programming by external button.