Hard-resetting an arduino

Question

I need to hard reset (or seriously breathe life into) a stuck Arduino clone (Sunfounder UNO) which doesn't get recognized by Windows (error 43) after installing the wrong sketch. I am using the latest Arduino toolset and, before today, the setup was functional.

The problem is probably that I am writing to the serial in the setup() section like this:

void setup() {
  pinMode(a0, OUTPUT);
  pinMode(a1, OUTPUT);
  pinMode(a2, OUTPUT);
  pinMode(b1, OUTPUT);
  pinMode(m0, OUTPUT);
  pinMode(m1, OUTPUT);
  pinMode(m2, OUTPUT);
  pinMode(OK, OUTPUT);
  pinMode(KO, OUTPUT);

  pinMode(carry, INPUT);
  pinMode(result, INPUT);
  delay(1000);

  Serial.begin(9600);
  Serial.write("Arduino Tester v. 0.1\n");
}

Arduino seems to be running the code. The problem is that Windows doesn't recognize it and doesn't set up a COM port for it.

So: i'd like to nuke it and restart from scratch.

How is this done?

Answer 1

The word "clone" immediately rings alarm bells.

Firstly, for a "normal" Arduino (like an Uno, etc) the sketch cannot influence whether Windows detects the board or not. All that is handled by a completely separate chip.

A lot of the cheap clones these days are coming out of China with a really really cheap USB serial adapter chip. These barely work at the best of times. Looking at the pictures I have found of your clone (the manufacturer's site is considerably lacking in any information whatsoever) it doesn't look like it's one of those chips, but one never can tell.

If they have followed the reference designs for the Arduino then it will be an Atmel ATMega32U4 (IIRC) chip that deals with the interface to the computer. That has firmware of its own on it, and if that has become corrupted (very unlikely) or damaged (possible) then it could cause it to not be recognised. If that is the case the in the former instance (corrupted) you will need to replace the firmware on it. For that you will need either a hardware ICSP programmer or another Arduino. In the latter instance you're stuffed, since you would need to replace the chip.

As I say that is unlikely.

Instead your problem is most likely actually with either Windows or the USB cable. You may need to remove and reinstall the Arduino drivers, or try a difference USB cable. Also try your "Arduino" on another computer.