PCA9555: Behavior after entering the OS.

Ariel Chang

Prodigy 20 points

Part Number: PCA9555

Dear TI member,

We know the INT pin is cleared by BIOS read IO expander.

We want to confirm that if the interrupt occurs after entering the OS, how can the IO expander INT pin be cleared?

Thanks.

Ariel

over 2 years ago

0 Clemens Ladisch over 2 years ago

Guru 317280 points

The interrupt is cleared when the port register has been read (see section 8.4.1 of the datasheet). Any edge on one of the port's inputs that happens afterwards will re-enable the interrupt.

If that happens, it is usually not a problem; the interrupt handler will simply be called again.

0 Ariel Chang over 2 years ago in reply to Clemens Ladisch

Prodigy 20 points

Hi Clemens,

Thanks for reply.

We want to confirm the behavior of io expander when entering the OS.

Under the OS, the bios has delivered control to the OS.
If we need to clear the INT pin at this time, how can we achieve it?

Thanks.

Ariel

0 Clemens Ladisch over 2 years ago in reply to Ariel Chang

Guru 317280 points

To clear the interrupt, read port input register.

I do not know what BIOS or OS you are using, or what their responsibilities are.

0 Tyler Townsend over 2 years ago in reply to Ariel Chang

TI__Mastermind 47998 points

Ariel,

I agree with Clemens' answer.

Conduct an I2C read on the input port register to clear the interrupt flag.

I am unsure about your point on the OS/bios. Can you provide a little more context to your situation?

Regards,

Tyler

Interface

Interface forum

PCA9555: Behavior after entering the OS.