CC2541: Simple BLE peripheral example false interrupt trigger

Venkatraman Balakrishnan

Part Number: CC2541

Hi,I have an rising edge interrupt on P0.5. I wake up the system on P0.5 and insdie the Port 0 ISr handler I clear the (port 0.5) P0IEN bit to disable the interrupt and I re-enable the interrupt when I go to sleep again. But there seems to be a false trigger when I reanable the interrupt i.e. setting P0IEN for P0.5. I see the ISR being called again due to a trigger as soon as I re-enable the interrupt. Am I missing something here? Is there a trigger supposed to happen after enabling the interrupt register?? I also see P0IF flag being set in IRCON indicating that interrupt is pending, which is not supposed to happen?

Please let me know.

Thanks,

Venkat

over 4 years ago

0 Severin Suveren over 4 years ago

TI__Mastermind 23730 points

Hi,

Could you post a code snippet of what you are actually doing? More context would help.

0 Eirik V over 4 years ago

TI__Guru 56590 points

Hello,

You need to clear the interrupt flag P0IFG, before you re-enable the interrupt.

Please refer to the User's Guide (SWRU191F):

When an interrupt condition occurs on one of the I/O pins, the interrupt status flag in the corresponding
P0–P2 interrupt flag register, P0IFG, P1IFG, or P2IFG, is set to 1. The interrupt status flag is set
regardless of whether the pin has its interrupt enable set. When an interrupt is serviced, the interrupt
status flag is cleared by writing a 0 to that flag. This flag must be cleared prior to clearing the CPU port
interrupt flag (PxIF). This is illustrated in Figure 2-4: There is an edge detect between the input line and
PxIFG, but no edge detect or one-shot between PxIFG and PxINT. The practical impact of this is what is
written in Section 2.5.1

0 Venkatraman Balakrishnan over 4 years ago in reply to Eirik V

Intellectual 360 points

Here is my code once an interrupt is triggered I enter the ISR clear the interrupt status flag and CPU port flag and disable interrupt for P.5 using P0IEN &= ~0x20; in my event handler.

//ISR handler

HAL_ENTER_ISR();
P0IFG &= ~0x20;
IRCON &= ~0x20;

//Call an event that disables the interrupt

HAL_EXIT_ISR();

And I reenable the interrupt from a seperate task event before the system goes to sleep.

P0IEN |= 0x20; // interupt enable

So after enabling the interrupt I was receiving an interrupt immediately even though there is nothing active in that pin.

===================================

Thanks Eirik,

Clearing the interrupt flag P0IFG, just before re-enabling the interrupt(in my task event) worked. But as mentioned earlier I am already clearing P0IFG in my ISR handler. May I Know why is that not enough ?? and why do I have to clear the P0IFG just before renabling P0IEN.

Is it possible that I recieved a bounce on the interrupt line and I received another interrupt between the time when I cleared my P0IFG in my ISR handler

and the time when I re-enabled P0IEN??

Please let me know.

Thanks again,

Venkat

0 Venkatraman Balakrishnan over 4 years ago in reply to Severin Suveren