ARM Technical Support Knowledge Articles

PORT LEDS DO NOT DISPLAY AS EXPECTED

Applies to: MCB2103 Evaluation Board

Answer


Information in this article applies to:


QUESTION

I'm using the MCB2103 and I'm having problems with P0.17 and P0.18 as GPIO; the ports appear stuck low (LEDs on MCB2103 always off). I can't write 1's to the ports and the BLINKY examples don't wiggle these pins either. I traced through the hardware and found nothing wrong. What could be causing this?

ANSWER

The current user manual for the LPC2103 states that these pins (P0.17 and P0.18) are always "open drain". If you want to use them as outputs driving HIGH, add two pull-up resistors (e.g. 10KOhm) to these pins, connecting them to 3.3V.

MORE INFORMATION

SEE ALSO

Article last edited on: 2006-11-30 13:53:47

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