Using analogue as digital issue

Projects Programming
1

Just testing using an analogue pin as a digital output using following:-

void setup() {
pinMode(A4, OUTPUT);
digitalWrite(A4, HIGH);
}

void loop() {
digitalWrite(A4, HIGH);
delay(2000);
digitalWrite(A4, LOW);
delay(2000);
}

The led flashes fine when sketch is first loaded. When power is disconnected then reconnected the sketch does not run. The L led on the Nano flashes aprox every second.

What am I missing here?

Steve

2

Nothing obvious wrong as far as I can see.

What happens if you use a normal digital pin ?

Put some Serial.print()s in the code so that you can see which code is being executed and how often.

Does the blinking change if you make the delay() values asymmetrical ?

Your code uses A4 but are you by any chance using A6 or A7 when testing on your Nano ?

Is anything else connected to the Nano ?

3

Plug:
The led flashes fine when sketch is first loaded. When power is disconnected then reconnected the sketch does not run. The L led on the Nano flashes aprox every second.

This does not happen in my case. After power cycle, the built-in LED of NANO lashes for 7 times and then begins the sketch which blinks an external LED + 2k2 at 2-sec intervval. We can also begin the sketch execution by pressing the RESET button or invoking the Serial Monitor.

4

You DO have a current limiting resistor in series with the LED...don't you? Just checking. :slight_smile:

5

Thanks for the quick responses but I've just clocked the issue.

I've been running the Nano from laptop USB while I've been writing this sketch.
When powering the Nano from the laptop in sleep mode or from a battery the sketch executes fine.
Never had this problem before?
All's well now.
Thanks again for your responses.

Steve

6

When powering the Nano from the laptop in sleep mode or from a battery the sketch executes fine.

Sorry but I don't get that. Are you saying that the program does not run properly when the Nano is powered by USB and the laptop is not in sleep mode ?

What type of battery are you using and how is it connected to the Nano ?