Wifi scan cycles the board off


Calling the following method cycles the board off and then on.

There are other modules connected to the board. Removing this call "resolves" the power cycle issue. The board will continue to cycle off / on until power source is removed.

Please advise.

Power. You don’t have enough current capacity on whatever you’re using, the call to the Scan() causes the board to draw more and then browns out/resets.

Add a better power source. Powered hub or external power.


@ Brett - Same result when using an energizer USB power pack.

It’s still a power issue though !

@ Brett - I have been further looking into your recommendation. Do you have any experience with a USB power pack that can power both Wifi RS21 module and T35 display connected to a Fez Spider board?

Using USB power of any kind is potentially a flaw in your approach, but the display plus WiFi is probably pushing the limits of the onboard regulators anyhow. Can you try the same process without the display? That’s a good way to show that it’s not the scan alone that’s causing this. To be sure, I’d flash the onboard LED several times quickly at startup, and then slow the flash rate down… then you’ll see that the board resets because the flashing will go back to the fast scenario briefly.

Also, not sure I know which board you’re using, can you add that to this thread so there’ a relevant track of it?

Onto USB. USB is limited, by design, to the amount of power a device can draw. If a USB powerpack decided it was only going to work in scenarios with low-power devices, it may not power your device properly. If you have a high-power phone charger that has a USB socket, I’d try that as most of those can deliver at least 1000mA which may keep you out of the danger zone

@ Brett -

I am not necessary married to USB, but the power source must be portable (from what I can tell, that limits options a bit). Wifi does work if the screen is removed from the equation. For reference, I am using a Fez Spider main board.

@ Brett - Here are details of the USB power pack I am currently using:

5 Volt / 4.3Wh (1150mAh)
See: http://www.amazon.com/dp/B002FU6KF2

mAh is a measure of capacity - so it can provide 1150mA for 1 hour, or 115mA for 10 hours.

What you’re hitting is a current draw (mA) that causes the supplied voltage to drop to a point that the board resets. You’ve confirmed that the reset doesn’t occur when the screen is on, so that just confirms this is the thing you’re seeing.

Is this Duracell charger new ?

@ Brett - I will further debug and let you know.

@ TechDev - Maybe you could work this into your design so you are not over-taxing the regulators on our USB power supply modules (which are limited to 800mA):


@ TechDev -
did you try a new cable between power-module and mainboard?
It was the reason for repeated rebooting in my case.