[SOLVED] Using V1 to lock V0 (both outputs)

Solved
1

Hi,

Just a thought experiment here, but is it possible for one virtual pin value to prevent the app changing the value of another virtual pin?

I ask mostly out of curiosity, but it would be interesting to use in my project. There’s a slider controlling V0, which controls the speed of a fan. Could I then use V1 in a menu widget which can lock the value of V0 (and therefore the fan speed) to specific values || allow full slider use? 100% PWM, 50%, off, custom etc etc.

I assume it would be an if(V1value)-else statement for the Arduino to ignore additional changes to V0 unless allowed by the value of V1, but can I lock the GUI by virtualWriting to V0 even though it’s being used for an app output?

Still waiting for a connection to a Blynk server (network firewalls and ports etc.) so I can’t currently road-test the idea, but could that work?

2

Hi.

Yes.

bool isLocked = false;

BLYNK_WRITE(V0) {
   if (isLocked) {
       //do no allow any change...
   } else {
       //some regular logic
  }
}

BLYNK_WRITE(V1) {
    isLocked = true;
}
3

Thank you. Will that also lock the V0 slider or will it just mean changing the slider position has no effect?

4

Correct.

5

Okay, I see. So the Arduino hunch was right, thank you.

My question was mostly whether there was a way I could lock the slider from the perspective of the app user, or at least have it re-update back into the pre-set position. Am I right in thinking that Blynk.virtualWrite(pin, value) won’t work for a virtual pin set up for sending data from app to microcontroller? The information would be gong the wrong way in my head.

6

No. However this feature is in todo list.

7

Okey doke, good to know. Good luck, and thank you for your time :slight_smile:

1 Like
8

Until then you could do something like this

bool isLocked = false;
int previousValue = 0; // some default value 

BLYNK_WRITE(V0) {
   if (isLocked) {
       //do no allow any change...
      Blynk.virtualWrite(V0, previousValue);
   } else {
       previousValue = param.asInt();
       //some regular logic
  }
}

BLYNK_WRITE(V1) {
    isLocked = true;
}

This should reset your slider if it’s " locked "

1 Like
9

That works a treat, thank you! I need to move the slider before it resets, but otherwise this works well.

10

Good to know, yea I imagined that would be the case on startup.
You could play with blynk sync functions to avoid that issue, didn’t have any of the code in my head for it :slight_smile: