Can't compile and flash over WiFi

Core connected to WiFI easily, using iPhone app, successfully Claimed.
After connecting to USB power, it shows up under Cores in the compiler.
Goes through the color cycle, and ends up in Breathing Cyan (BC.)
The second I click Flashthe Core briefly flashed Blue (I’m pretty sure - it’s quick),
then spends a long time in (slow) Flashing Cyan, briefly switch to Fast Flashing Cyan,
then back to slow FC. Eventually passes through a couple seconds of flashing Green (or Yellow, maybe both), then back to BC.
All this time, the compiler is still working on Blink An LED (unmodified fork.)
Finally, compiler times out, and goes to Ready, never having flashed the Core.

I’ve tried this many times, with and without Core reboot, with the same results.
I’m ~6 feet from my WiFi router, ni the same room.


Hi @dbell,

Make sure you click “verify” before you click flash. The build site status message is a bit misleading right now (just logged another bug for this).


I had done a verify, but tried it again just now.
This time ,it doesn’t reset the Core into the color cycle, but as usual “The request seems to take longer than usual. Please be patient…”.
Eventually, I expect it to go to “took too long / timed out” and Ready.

So far, totally disappointed…

After clicking flash are you sure the slow flashes are cyan (blue) or magenta (pink), I have an issue which is described here

Adding the following two lines to setiup() resolved the issue for me.


Hi @dbell,

Sometimes user firmware can cause the core to lose its connection, if you’re having trouble doing an OTA update, try a factory reset first to reset your core to totally safe firmware which can help. Or if your core is having trouble staying online on your network, you can always flash locally as well! Instructions for that are here:

We’re also working on a command line tool that will simplify local flashing as well.


Not sure what you mean by “user firmware”. This is straight out of the box, linked and claimed by iPhone app, works with Tinker, as far as I can tell. The sketch is completely unmodified and as basic as it hets - Blink An LED. The compiler takes forever, then times out, never apparently flashing the Core.

A local (USB) tool would be great!


I guess that’s a good question; i am sorta colorblind! But they look exactly like the “breathing cyan”.

I’ll try adding the serial startup.

Asked my wife - you’re right, the slow flashing was magenta.
Adding the serial start code didn’t seem to help, though.

Ah, sorry about my lack of distinction on firmware @dbell ! :smile:

The “compiling” message on the build site is misleading, so we’ve changed the status message. It used to say “compiling”, but now it should say: “flashing, your core should start flashing, etc”.

The compile step usually takes less than a second, but the flashing process can fail or not start if the core isn’t online, so I’m hoping this message is more empowering! You can tell the firmware flashing vs. breathing by the change in intensity. The OTA flash will go full on / full off 3-4 times a second, connected ‘cyan breathing’ will slowly go from off to on over a second or two.


OK! I finally have something working, flashing the User LED on D7.
The “Compiling code…”/ flash process still took the best part of a minute, for 6-8 lines of code, and the same message is still sitting st the bottom. Eventually it will say it timed out and go to Ready.

Thanks for the help,


Hi @dbell,

If you haven’t recently, refresh the build page to get the updated messaging.

The flashing process right now does take somewhere between 20-60 seconds depending on the latency of your internet connection. We have a fix in the works that should increase the flashing speed significantly. Glad you got it working!


Yeah, after refreshing the compiler page, the new messages are working.
Still took nearly a minute to complete flashing, and a couple minutes later, it still says it’s flashing code.
That’s some serious latency! My data connection is fast enough (6.5Mbps down, 2.5 up); is a 32mS ping time slow? Does the OTA flash create and tear down connections rapidly?

(BTW, compiler still thinks it’s working!)


Tried again, using Chrome instead of Firefox. Speedtest under Chrome is much faster download rate (22+ Mbps), but overall, compiles exactly the same.

I think the big factor would be the latency between a client on your wifi network and the cloud server. A 100ms ping would cause something like 15-25 seconds of delay during flashing.