Hi,
this is my first post here, steadily learning ARM but I have a lot of problems doing so :)

I am trying to get external interrupt up and running on my Olimex LPC P2148 board (link). I am using ENT1 so I have a wire connected to P0.3 (SDA0 on the board) which I want to trigger an interrupt with if I short it to +3.3V (rising edge, eventually I want to trigger using a photodiode input but for now this will simulate that).

I am using Crossworks and CTL to configure the interrupts easily, below is the code I use to initialize everything:

PINSEL0 = 0x000000C0;
ctl_set_isr(15, 1, CTL_ISR_TRIGGER_POSITIVE_EDGE, YSync_IRQ, 0);
ctl_unmask_isr(15);

The thing is: this code works and triggers an interrupt BUT it only works when I short P0.3 to ground (!), so it's currently operating in LOW LEVEL mode, not rising edge as I want! I can verify this because P0.3 is at 3.26V whereas this should be 0V to get a correct rising edge reading I think?

What exactly am I doing wrong or what do I have to do to get my piece of code running? I've been looking at this for a long time now, can't seem to get my head around it, all the help I can get is much appreciated!

Nils Start a New Thread

check the errata

Nils Tijtgat wrote:
>
> Hi,
> this is my first post here, steadily learning ARM but I have a lot of
> problems doing so :)
>
> I am trying to get external interrupt up and running on my Olimex LPC
> P2148 board (link ). I am
> using ENT1 so I have a wire connected to P0.3 (SDA0 on the board)
> which I want to trigger an interrupt with if I short it to +3.3V
> (rising edge, eventually I want to trigger using a photodiode input
> but for now this will simulate that).
>
> I am using Crossworks and CTL to configure the interrupts easily,
> below is the code I use to initialize everything:
>
> PINSEL0 = 0x000000C0;
> ctl_set_isr(15, 1, CTL_ISR_TRIGGER_POSITIVE_EDGE, YSync_IRQ, 0);
> ctl_unmask_isr(15);
>
> The thing is: this code works and triggers an interrupt BUT it only
> works when I short P0.3 to ground (!), so it's currently operating in
> LOW LEVEL mode, not rising edge as I want! I can verify this because
> P0.3 is at 3.26V whereas this should be 0V to get a correct rising
> edge reading I think?
>
> What exactly am I doing wrong or what do I have to do to get my piece
> of code running? I've been looking at this for a long time now, can't
> seem to get my head around it, all the help I can get is much appreciated!
>
> Nils Start a New Thread

--- In l..., Nils Tijtgat wrote:
>
> Hi,
> this is my first post here, steadily learning ARM but I have a lot of problems doing so :)
>
> I am trying to get external interrupt up and running on my Olimex LPC P2148 board (link). I am using ENT1 so I have a wire connected to P0.3 (SDA0 on the board) which I want to trigger an interrupt with if I short it to +3.3V (rising edge, eventually I want to trigger using a photodiode input but for now this will simulate that).
>
> I am using Crossworks and CTL to configure the interrupts easily, below is the code I use to initialize everything:
>
> PINSEL0 = 0x000000C0;
> ctl_set_isr(15, 1, CTL_ISR_TRIGGER_POSITIVE_EDGE, YSync_IRQ, 0);
> ctl_unmask_isr(15);
>
> The thing is: this code works and triggers an interrupt BUT it only works when I short P0.3 to ground (!), so it's currently operating in LOW LEVEL mode, not rising edge as I want! I can verify this because P0.3 is at 3.26V whereas this should be 0V to get a correct rising edge reading I think?
>
> What exactly am I doing wrong or what do I have to do to get my piece of code running? I've been looking at this for a long time now, can't seem to get my head around it, all the help I can get is much appreciated!
>
> Nils
>

Try adding a pull-down resistor (say 1k) between the pin and ground. I imagine the pin is just floating high.

The code is probably working in the mode you want because the method you use to pull the pin to ground probably allows it to bounce high. You will want to be careful you don't get a BUNCH of interrupts when you just scratch a wire.

Richard

Start a New Thread