Debouncing GPIO1-3 interrupt lines

Joe Schirmer

I have configured a GPIO (GPIO3[3]) as a interrupt source for both rising an falling edge. This works just fine so long as I don't enable debounce on the line at which point the GPIO no longer produces interrupts! The only difference between the working and non-working code are two lines of code where I set GPIO3.GPIO_DEBOUNCINGTIME=0x000000FF (for approximately a 7.9 ms debounce time) and then I set GPIO3.GPIO_DEBOUNCENABLE=0x00000008 (to enable debounce on GPIO3[3])

Am I supposed to also turn on / enable the CLK_32KHZ that is used for debouncing on GPIOs 1-3? The TRM mentions pd_per_gpio_3_gdbclk in section 25.2.2 (Table 25.3) but it is found nowhere else in the TRM so I am not sure how to configure it.

over 12 years ago

0 Biser Gatchev-XID over 12 years ago

TI__Guru**** 393215 points

Hi Joe,

If you route the GPIO input through the debouncing cells, then you definitely need to turn the clock for these cells on. This is mentioned right at the beginning of section 25.2.2

Best Regards

Biser

0 Joe Schirmer over 12 years ago in reply to Biser Gatchev-XID

Prodigy 81 points

Yes, that may be true but the TRM does not describe how to turn on the CLK_32KHZ used by GPIO1-3 debounce logic.

0 Biser Gatchev-XID over 12 years ago in reply to Joe Schirmer

TI__Guru**** 393215 points

The relevant TRM parts are Figure 8-17 and section 25.3.4.4. I think that except for GPIO0, the debounce clock is always present.

0 Joe Schirmer over 12 years ago in reply to Biser Gatchev-XID

Prodigy 81 points

If the debounce clocks are always enabled for GPIO3, then why do I stop getting interrupts on GPIO3[3] when I enable debounce? What else may I be missing?

0 Biser Gatchev-XID over 12 years ago in reply to Joe Schirmer

TI__Guru**** 393215 points

Have you setup everything as described in section 25.3.4.4 of the TRM?

0 Joe Schirmer over 12 years ago in reply to Biser Gatchev-XID

Prodigy 81 points

Yes, i have:

Configured GPIO3[3] as input and enabled rising edge and falling edge interrupt for GPIO3[3].
Set GPIO3_DEBOUNCETIME=255 for GPIO3.
Set GPIO3_DEBOUNCENABLE=0x00000008 to enable debouncing for GPIO3[3]

Interrupts work when I do the first bullet but not when I do the other two.

0 Biser Gatchev-XID over 12 years ago in reply to Joe Schirmer

TI__Guru**** 393215 points

Hi Joe,

Please check TRM section "8.1.12.1.1 CM_PER_L4LS_CLKSTCTRL Register (offset = 0h) [reset = C0102h]", register bits CLKACTIVITY_GPIO_X_ GDBCLK. It seems that the GPIO debounce clocks are disabled by default and need to be turned on. Sorry I missed this before.

Best Regards

Biser

0 Joe Schirmer over 12 years ago in reply to Biser Gatchev-XID

Prodigy 81 points

CLKACTIVITY_GPIO_x_GDBCLK are all read only.

0 Joe Schirmer over 12 years ago in reply to Joe Schirmer

Prodigy 81 points

I tried setting OPTFCLKEN_GPIO_3_GDBCLK (bit 18) in CM_PER_GPIO3_CLKCTRL (offset 0xB4) and that seemed to do the trick. Interrupts are once again working and debounce is enabled.

It might be nice if the next rev of the TRM was a little more explicit on this. The field description should specify that this bit will enable the debounce clock (currently it is described as an "optional functional clock") and section 25.3.4.4 should mention this field as well.

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Debouncing GPIO1-3 interrupt lines