Intermittent WiFi Connection at Startup

[tfjield]

@mintytrebor
Good advice! In my case my 2.4 GHz network has a separate SSID just for that reason, iot devices often aren't smart enough to navigate a dual network.

I have had these issues with the Duet since day one. I added another AP to try to improve the situation, but it didn't help. And I recently scanned everything to make sure all was clear.

Seems a bit coincidental that both of us with problems are running Unifi... It's not THAT common. But could be a coincidence.

I really think there's either some kind of race condition. I thought it might be a voltage stabilization issue at startup, but since I get the same problems when I deactivate and reactivate the WiFi module, I don't think that makes sense.

[tfjield]

@exerqtor
But the fact you didn't have problems with the Duet 2 suggests that it's not the network and something about the specific Duet board...

[Phaedrux]

When and where did you purchase the Duet 2 Wifi?

[tfjield]

@phaedrux
It came with my Modix printer. I received it about 2 weeks ago. It was shipped with the other parts direct from China.

[Phaedrux]

Do you have another spare access point to test with? It would be good to isolate the issue before we go through the trouble of warranty replacement incase that won't actually solve the issue.

[tfjield]

@phaedrux
I do. It had the same problem with the AP in the house, so I thought maybe it needed a higher signal strength, so I put a new AP close to it. (The strength was good already, but I didn't want to be blasting everything else indoors if it needed more.) But I can crank up the indoor power temporarily and try connecting to that one again (different SSID's, so that's easy) to see if it makes a difference.

I can't do this until Monday, though. I'm sitting in a plane just about to take off! ️

[oliof]

@tfjield is that still another Unifi AP, or some other make/model?

[tfjield]

@oliof It's Unifi. The current is model UAP, and the other one I can test is U6-LR.

[tfjield]

@oliof @Phaedrux
I may have found something. On a hunch, I decided to replace the SD card with a faster one, thinking that there might be some kind of race condition occurring during startup.

The card that came with it is a SanDisk Edge 8 GB class 4. Here's a stock image of the card:

I replaced it with a SanDisk Ultra.

With the original card it would boot and connect to WiFi no more than half the time. After replacing the card, it's connected 5 out of 5 reboots. I'll continue testing, but it seems much better!

EDIT: This is on the same AP; I've only changed the card.

[Exerqtor]

@tfjield Interesting, keep us updated on this please 😅

[tfjield]

@exerqtor
With the new card I've rebooted about 18 times so far, and it's only failed twice. Looks like a significant improvement, but not 100%.

To be completely sure it's not something else, I'll swap the old card back in later and see what happens.

[tfjield]

Well, it turns out that this was not the fix. As time went on, the number of times it would fail vs. the number of times that it would succeed has increased a lot. We're back to 50/50 or greater failure rate.

To this day, once the WiFi is connected I have never lost connection.

I suppose this could be a hardware problem, but it sure seems more like some kind of race condition. Is there anything I can do to help determine the root cause for the failure?

[Phaedrux]

Can you snag a close up pic of the soldering on the wifi module?

[tfjield]

@phaedrux
These aren't great... Is there something specific you're looking for? If so, I can try to highlight it better. And these were with a cell phone camera... If these aren't good enough, I can pull out the USB microscope.

[Phaedrux]

Thanks for the photos. I will pass them on for evaluation.

[Phaedrux]

I don't suppose you could get some better photos? Might have to take the board out.

[tfjield]

@phaedrux Sure, I can get better photos. Anything in particular I should try to capture? Are you looking for a cold solder joint? Perhaps it would be better if I viewed it from a 45° angle...

[tfjield]

@phaedrux Here are some better pictures. I tried to image near the pads on the bottom.

That's about the best I can do.

[Phaedrux]

Thanks I'll pass those along.

[dc42]

@tfjield thanks for the photos.

I think the soldering is OK. The WiFi modules have gold plated recesses on the sides - see photo below. The solder appears to have wicked up int those recesses, so it should be making good contact.