David Fletcher

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8 years, 11 months ago.

LPC1768 pin p15

I am having trouble with pin p15. I was using 2 push button interrupts one on p14 the other p15, when i push on either button, i get an indication that both interrupts have fired. I changed the pins to p15 and p16, the result was the same, so i changed the pins again to p14 and p16, which gave me the result i was expecting. I can only assume there is a bug in the mbed lib. Is this a bug? Or have i just lost the plot?

Update: I tried the same program on the LPC4088 and it was ok using pin p15, so i tried the LPC1768 again with p15 and now it is also ok. I have not changed anything, so i don't know what is going on. At the moment i am putting it down to having a bad day!

1 Answer

Wim Huiskamp
8 years, 11 months ago.

Could be software, but Interrupts should work on the numbered pins except for p19 and p20. Make sure you have pull-up Rs on the pins when the button connects to GND. Floating (interrupt) pins can sometimes be influenced by the pins next to it (possibly static or 50Hz noise from your finger on the button..).

@Wim I am using a hard pull down using 1K Rs, looking for a rising edge, i also checked with a scope, nothing to see! Why i think it may be a bug, is that my app was reporting p15 being triggered first, even though i had triggered p14. Maybe I am having a bad day?

posted by David Fletcher 22 May 2015