2

I have something strange going on with an output. When the following code is called the LED goes on, but it stays on, there is no blinking. If I comment out the set HIGH statement the LED never comes on (as expected).

#define devicePin 10

void setup() {
  pinMode(devicePin, OUTPUT);
}

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

Could I have damaged the board in some way?

5

After you drive the pin low, you immediately go to the beginning of the loop and set the pin high (if you have an oscilloscope, you might see a very short downward pulse).
So, add another delay after digitalWrite(devicePin, LOW).

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3

you forgot to add a delay after digitalWrite(devicePin, LOW);

#define devicePin 10

void setup() {
  pinMode(devicePin, OUTPUT);
}

void loop() {
    digitalWrite(devicePin, HIGH);
    delay(2000);
    digitalWrite(devicePin, LOW);
    delay(2000);
}
| improve this answer | |
2

Yes, the pin is going low. I tested it for you:

Pin 10 going low

It went low for 6 µs, once every 2 seconds. :)


Overall, this is the effect:

Pin 10 mainly high

As you can see, high for most of the time.

| improve this answer | |
  • Yeh, I can't believe I missed it. BTW: what did you use to monitor it and create those screens? – P Hemans Sep 13 '15 at 5:01
  • 1
    My trusty Tektronix TDS 2002 oscilloscope. To get the output I get the scope to output in PCX format through its RS232 port, route it through a RS232 to TTL converter, connect that to a FTDI cable, and capture it on my computer. That scope was made in the days before they had plug-in USB drives. – Nick Gammon Sep 13 '15 at 5:04
  • One more question, what would you recommend now for an entry level scope? – P Hemans Sep 14 '15 at 8:37
  • 1
    You are probably best off with one of the Saleae Logic scopes/logic analyzers. Something like the Logic 4 is only $109 and has one analog and 3 digital channels. Or one of the higher models if you can afford it. I find the Logic very very useful for decoding SPI/I2C/Serial data streams. You could make this a separate question, others may also want to chip in with their suggestions. – Nick Gammon Sep 14 '15 at 20:32

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