Currently I'm working on building up a test board to validate my code before adding the external hardware. Basically, I am using switches and LED's to prove out my sketch and make sure events are happening (LED's are lighting) when expected. For the sake of simplicity, I won't get into the code, that is not where the issue is. (Dumbed it down to a simple sketch to output high on LED pins to make sure they are illuminating).
So here is what I am seeing: Pins 2-21 are all outputting as expected. Running LED's with a 220Ohm resistor, they illuminate nicely.
Then I get to testing my Outputs on the header of 22-53. This whole header seems to put out less. Depending on LED color, it either does not illuminate, or barely illumates. (I've checked the Same LED's on pins 2-21 - they work fine there). I checked the No load voltage, it's right at 5V. Under load, either 22-53 has a drop across the LED of 2.4V, while pins 2-21 show a drop of 3V across the same LED, with a 200 ohm in series. I can't seem to measure current, or I would report it. Should be easily calculated, though.
Anyone know what is going on? Do I have a faulty board?