Ok I see. I suggest you start with one LED like you are doing to make sure all is good first then connect more.
Let us skip the FET for a sec, connect a small LED directly to a pin and try to dim it using PWM.
Hi Gus,
I did what you suggested by putting the LED directly in the pin. It is working and dimming as I expect. However, my oscilloscope shows the top of the square wave at 2.4V.
Even turning on the digital pin with this code results in 2.4V
OutputPort LED = new OutputPort((Cpu.Pin)FEZ_Pin.Digital.Di0, true);
LED.Write(true);
I am not powering the FEZ using external power just the power coming out of my USB connection with my laptop.
I thought the Voltage was suppose to be 3.3 or 5 right?
did you add a current limiting resistor as expected?
Remove the LED and leave the scope, do you see 3.3V?
No resistor at all. Positive pin of LED directly in Di1 the other end directly to ground.
I googled “how ot connect led to a micro” and the first link was http://www.siriusmicro.com/projects/b2.pdf
Have fun 
Oh thanks a lot! It has some great info but nothing about operating a transistor from the pin. What are your thoughts about the voltage I am seeing. Is that normal?
If you do not have a current limiting resistor in series with the LED you are allowing the pin to source more current than it is designed to handle. The voltage will sag; if it didn’t you’d smoke the LED and/or the micro. Seeing 2.2V in this case is not unreasonable.
If you are PWM’ing the output your voltmeter will read something between 0 and 3.3V. It should read 3.3V times the duty cycle. 50% duty cycle will make the pin look like it’s outputting 1.65V (50% of 3.3V). The meter can’t show you what’s really going on (the output rapidly toggling between 0 and 3.3V), but an oscilloscope would. The meter is reporting the average voltage (1.65V in the 50% example).
Below is a schematic for driving the LED / LED array with a transistor. It will work with PWM or single-send outputs from the domino. A FET does not draw any significant current through the connection to the domino.
With nothing connected you should see 3.3V on a high output pin.
With 220 ohm and an LED connected you should see something very close to 3.3V
With the transistor connected you should see 3.3V at the domino pin, when high.
I am still looking for reasons why my pin is showing 2.6v 
OK, so here’s the next test I would like to see.
Simple test app that sets all pins HIGH and then LOW and you measure the voltage across all them to see if it works as expected.
(pseudocode)
while (1)
{
set all Di0 to Di13 high;
toggle LED on;
sleep(60,000);//sleep for 60 secs
set all Di0-Di13 low;
toggle led off;
sleep (30000);
}
Check what the spread of voltages is. Also you should measure the output voltage from the regulator to see that this hasn’t failed.
Thanks WhysItSmoking!
I appreciate the advice. I will be running 4 rows of 18 lights. So need the right power and MOSFET. It looks like the specs for the 2SK3065
will be great especially because my pins are at 2.6volt on my Domino for unknown reasons. I’ll be testing Brett’s idea tonight.
I have used this little mosfet breakout to drive stuff. Works great and the RFP30N06LE should be able to drive almost anything you will craft and at logic level 3v. 2.6v might not fully close it, not sure, but for $4, it is worth a place in your parts box.
[url]http://www.sparkfun.com/products/10256[/url]
Another option would be this simple logic level converter using the BSS138 mosfet. For $2 buck, also a good one to have around. I can’t remember at the moment, but you may have to reverse your logic using this one as both sides pulled-high by default.
[url]http://www.sparkfun.com/products/8745[/url]
And some background on the method used which is kinda cool.
[url]http://ics.nxp.com/support/documents/interface/pdf/an97055.pdf[/url]
cool I’ll check it out. I have not had time to fully do the test on all the pins and now I am heading to Kauai for the week. I will return!