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External power without usb debugger on Panda or Panda 2


I can’t seem to find out how to do this, or perhaps I did see this and I wasn’t smart enough to recognize what I saw.

I have a 9v transformer to plug into the board and when I do that without the usb plugged in, nothing happens other then the LED lighting up.

I’m sure there is something more that I have to do, where can i find that info?


What is it supposed to do? :wink:

Did you load a program?


When I debug through VS2010, it runs my program, flashes the LED and sends data over the network to my server.

None of the happens when I unplug the usb and plug in the 9v power.


I assume the 9V transformer is a DC power source.

What is the current rating of the 9V power source? Can you measure the voltage when it is connected?

What are you using to attached to the network?


Yes, 9v DC. I can’t measure the source now (it’s located somewhere else), but even if I could the only thing I know how to tell you is what is on the label.

I’m using the FEZ Connect (the one with the RJ45 adapter on it). This all works when I am debugging.

Maybe I am not doing something correctly when I am putting the code onto the board? Is it the same process as debugging? (VS2010 -> Deploy)?


There is an outstanding question on the current capacity of the 9V source. It might be able to provide enough current to the Panda and FEZ Connect. Check out the label.

Once you deploy via VS2010 the code should stay in the flash memory on the board and run when powered up.

When you run without the USB cable timings can be a little different and that could be resulting in an unhandled exception.


Ok, the transformer that I am using is this

the code I am running is this

using System;
using System.Threading;

using Microsoft.SPOT;
using Microsoft.SPOT.Hardware;

using GHIElectronics.NETMF.FEZ;

namespace FEZ_Panda_II_Application1
    public class Program
        public static void Main()
            OutputPort led = new OutputPort((Cpu.Pin)FEZ_Pin.Digital.LED, false);

            while (true)




Right now when I test the board, there is nothing attached to the Fez Panda 2 (it is just the fez panda 2).

If I debug, everything works. If I supply power through USB (using a usb wall charger) everything works. When I use the adapter, the led turns on (and that is it). And finally if i plug the USB power back in, it works.

I have tried 3 different adapters ranging from 250ma to 500ma (all 9v) and everything behaves the same.

(Currently I have no way of testing the current coming out of the adapters (My electronics skills are lacking, and so is my electronics tool box).


And nothing is connected? no shields nothing?


nothing. It’s just the Fez Panda 2. (I removed the other shields to make sure they were not causing the problem).


then I suspect your 9v 250ma and 9v 500ma power supplies are not capable of powering your device with sufficient current. It could be the VREG on the board not performing up to spec, but my guess would be the power supply is not up to the task as a first .

I can’t find anything that tells me that this is a reputable brand that has good quality control, so you may have duds. The other thing is that 250ma is very low, I’d suggest you need 500ma as a minimum, 1000ma would be better. You should look at a higher level of quality power supply - check out adafruit or sparkfun for an option. Especially if you have more shields to be part of your project, it seems to me that you definetely want a larger supply.

Also remember that the further away from 6.5v you go the more work the onboard voltage regulator must do, so you’re better off with a 6.5v 1a supply than a 9v 1a supply - you can get a feel for the temperature of the VREG as an indicator how much regulation it has to do, but be careful as it can be very hot.



judging your previous code, you don’t need to use external power source in this case. cause…
it’s working on your LED (see your FEZ panda board, and see the LED beside the USB connector). it’s working on me now, and i’m not using external power source yet


We need some clarity on one thing - you say the LED comes on when you only connect the 9v supply, which I assume means that it doesn’t flash.


Ok, today I happened to be digging through my tool pile in the garage (looking for a flat head screw driver which I never found) and I found a 750ma 6v AC/DC transformer. I plugged that baby into my board and everything started working correctly!