X2 Port C Pins Available w/o LCD?

I’m evaluating the X2 before purchase and I’m curious to know whether I can use the PortC pins as regular digitial i/o if I don’t have an LCD connected?
From the block diagram it seems like these are just i/o pins going to the LCD connector. But I’m not sure if there are any intermediate electronics on those lines.
I expect to attach a nordic RF module which needs 6 i/o lines, and I have other (TBD!) constraints so I’m looking to see how many i/o lines I can get on the x2.

Nordic RF: sparkfun.com/commerce/produc … cts_id=705


No funny business, all the I/O pins of PortC, plus three pins from PortB, are wired straight to the header pins of the LCD connector. Conveniently it also has 5V power (pin 2) and a ground pin (pin 1) so it would be great for plugging in some other device.

Less obvious from the schematic, pins 15 and 16 on the LCD connector are for the LED backlight anode and cathode. There’s a 9.1 ohm resistor on the power side and a mosfet on the ground side to allow you to disable the backlight, so don’t mistake these for the straight power and ground pins.



If you take a look at the X2 schematic, you can see that five of the PORTC pins go to LEDs and the other three go to user push buttons. You can still use them as general I/O pins so long as your input source is capable of driving those the lines with LEDs on them hard enough. Otherwise, the LEDs will act as pull-downs that will keep your input source from being able to generate a high signal.

- Ben

Whoops! Ben’s totally right about the LEDs. I looked at the schematic, and even got out my X2 and looked at the traces, and I still missed that. I think I learn as much trying to answer questions as I do asking them!