Value Display - displays wrong value on app re-connect


I am working away from home with limited internet connection for a week. I’ll contact you when I am back home.

I have the project with me and am now running it on local server due to lack of Internet. It might be noteworthy to you that the problem does not occur while using the local server running on a RP. It is the latest version of the local server.

Running the exact same Arduino code, same hardware, just connecting to local server instead of cloud server. Weird.

Yes, this is very weird. Any chance you have some script/other clients that write data into that pin?

Not on purpose, I’m not that talented :smiley:

I will keep you updated if I find anything.
I’ll be back on cloud server in a few days.

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I might be getting a little closer to an answer on this. It seems like whatever text is written to the display widgets at the time of completely logging out of the Blynk APP is written back into the display widgets whenever the project dashboard is minimised (another blynk project brought to the foreground) or if the app is closed and reopened.

At some stage I must have logged out with a value of 11 written to that Vpin.

What do you think? Does it make sense?

Indeed this is feature. Blynk restores latest value server had got from hardware.

I have this same problem. I have a medium label associated with V9. It shows values in the range of 0 to about 10. When I start the Blynk app on my IOS device it briefly displays a value that looks about right - such as 3.2. However after about a second it refreshes the display and shows 100.7. Note my IoT device is offline the entire time. If I turn my device on, then it will send (push) a normal value in the 0 to 10 range and blynk app updates the screen and displays it. When I exit blynk app (on IOS, swiping up to close app, or I can log out and close app, or I can just minimize) then re-open blynk app, with my IoT device off line, it will again show a correct looking value for a moment and then refresh and again show the mysterious 100.7.
Here is another clue to this problem… I used to use V9 to display a different parameter (also a push), and for that parameter values were in the range 99 to 110. So a 100.7 would have been a value that could have been displayed. It seems like the blynk server has cached on old value for V9, and it always reverts back to that when the app opens and can’t connect to the device. Note that it does briefly display a correct value before reverting to the incorrect value. Seems to me like there is a bug in the blynk feature to save and display cached values. It does display a correct cached value, but then a moment later somewhere in the blynk server code it refers to some ancient cached value that has never been updated to the latest cache value.
Let me know if you need me to send you any further specifics to help solve this problem.
I have tried deleting the widget and creating a new one, still associated with V9. This doesn’t get rid of the problem.
I think the IoT device being offline is a factor in this problem. In my case, for power considerations, my IoT device (ESP8266) deep sleeps for 5 minutes then wakes up for 6 seconds while it pushes data. So most of the time when the app is started the device is intentionally offline. I can’t afford the power to keep wifi up and an active connection with blynk server. Hence I’m heavily dependent on the cached initial value feature, and hence affected by this issue.

Hope this gives you enough clues to fix it.

I found that the ‘ghost’ value is the value that the Blynk server had for that Vpin the last time you completely logged out of the Blynk server.

Try completely logging out when the value is within the 0-10 range then see if you can help prove this theory

Ok, I waited till the display showed a number in the 0 to 10 range (it was 2.6), logged out and exited app. Reopened app and logged back in. On the screen where you choose which project you want to open (ie swipe left to get to create a new project) the image of the project showed the 2.6 value. When I click that image to open that project, the ghost value (100.7) appears again.
If I then click the square button (stop) in top right corner, and then hit the triangle (play) to start the project again, it updates and displays the right value (2.6).
If I then click top left button to go back to project list, it shows the correct value in the image of the project on the project select screen. If I think click the project, it starts it and value goes back to 100.7.

So it seems when it gets one value when displaying the project list (and that one gets updated to whatever value exists when you logout). But it gets uses some other variable to get the initial value when the project starts (perhaps only when IoT device is offline). It’s this other variable that has the ghost value still stored in it.

Note also, that the ghost value is appearing in a “labelled value” widget. I also have a history graph that uses data from same virtual pin - the graph never shows the incorrect ghost value - the graph is always right. Hope that helps.

Hi Russ, good description of the problem that I was also having. It sounds exactly like what I was experiencing.

For some reason it is no longer happening in my project yet I have not changed anything. I hope your description of the issue helps find the root cause.

Russ, do you use cloud or local server? I just remembered I was only experiencing the issue using cloud server. Now I am running local the issue seems to be gone.

I’m using the cloud server.

I’ll switch back to the cloud and see if my issue comes back. Will be tomorrow before I get time.

I have the same problem: when I open the app I see some very old values (few months) until my project pushes values to the Blynk server (every 5 seconds).

It would be nice if the display showed the last value or stays blank until new data is received.

Just FYI - I uninstalled and reinstalled blynk app on my smartphone - just to see if it would make a difference. It didn’t. The problem is still 100% reproducible on demand.

@Maarten_CH do you have also iOS?

I have not yet had the time to convert back to cloud server to see if the issue comes back for me. I will try and do it in the next 24 hrs

@Dmitriy, yes, latest version of iOS/Blynk.

Edit: I just realized that when I swipe to a different project I do see the values from the last reading when the window is still small, going to blank when the project window is selected/maximized until the new values come in. I think this is the correct/desired sequence.

I’m not sure if it’s related but it’s the oldest project that shows the strange behavior.