Detect Lows and highs and rising falling edges on input pin P21

RE: Detect Lows and highs and rising falling edges on input pin P21

snoopy20 — Sun, 16 Jul 2023 19:50:33 GMT

There's something wrong. Post your pin config.

Here's some code showing how to detect a signal on a pin and fire the interrupt.

NRF_GPIO->PIN_CNF[CFG_PIN_MOTION_ZEROCROSS] = GPIO_PIN_CNF_DIR_Input << GPIO_PIN_CNF_DIR_Pos;
NRF_GPIOTE->CONFIG[CFG_GPIOTE_MOTION_ZEROCROSS] = GPIOTE_CONFIG_MODE_Event << GPIOTE_CONFIG_MODE_Pos | GPIOTE_CONFIG_POLARITY_HiToLo << GPIOTE_CONFIG_POLARITY_Pos | CFG_PIN_MOTION_ZEROCROSS << GPIOTE_CONFIG_PSEL_Pos;

NVIC_SetPriority(GPIOTE_IRQn, CFG_INTERRUPT_PRIORITY_GPIOTE);
NVIC_EnableIRQ(GPIOTE_IRQn);
NRF_GPIOTE->INTENSET = 1 << CFG_GPIOTE_MOTION_ZEROCROSS;

void GPIOTE_IRQHandler (void) {

...

NRF_GPIOTE->EVENTS_IN[CFG_GPIOTE_MOTION_ZEROCROSS] = 0;
__DSB();
}

RE: Detect Lows and highs and rising falling edges on input pin P21

Tarik — Fri, 14 Jul 2023 12:39:47 GMT

Hi,

I tried resistors from 300K down to 65K and the high input voltage has increased from 0.9V to 1.2V. which is not enough for high edge detection.

My original logical high voltage is 4.7V

Does that mean I should keep lowering the resistance until I get the desired high voltage, or is there something wrong ?

Thanks

RE: Detect Lows and highs and rising falling edges on input pin P21

snoopy20 — Thu, 06 Jul 2023 11:42:19 GMT

correct

RE: Detect Lows and highs and rising falling edges on input pin P21

Tarik — Thu, 06 Jul 2023 10:53:16 GMT

I am powering the NRF52 at 3.3V, which means the minimum High logic I can detect is 2.31V, which should still work, right ?

No problem with noise, as long as it does not trigger false edge detections.

Thanks for the help

RE: Detect Lows and highs and rising falling edges on input pin P21

snoopy20 — Thu, 06 Jul 2023 10:48:52 GMT

Noise suppression and skew. If it's a digital signal it will have little skew and a 100k -1M will work.

You must run the NRF52 at 3.6v or the high may not be detected.

Pin config -> you need to read all the datasheet and learn about the peripherals, specifically GPIOTE and GPIO Latch.

RE: Detect Lows and highs and rising falling edges on input pin P21

Jared — Thu, 06 Jul 2023 10:44:11 GMT

As long as you can guarantee that the voltage is within the absolute maximum ratings as stated in the ps, then it should be ok,

regards

Jared

RE: Detect Lows and highs and rising falling edges on input pin P21

Tarik — Thu, 06 Jul 2023 10:34:49 GMT

Thanks for the reply.

I am looking ideally for the cheapest solution, what do you think about adding a series resistor to the pin ?

RE: Detect Lows and highs and rising falling edges on input pin P21

Tarik — Thu, 06 Jul 2023 10:33:44 GMT

Thanks for the answer,

Is there any drawback I should consider when using the series 100K resistor ?

Also what Pin configuration do you recommend using ?

RE: Detect Lows and highs and rising falling edges on input pin P21

Jared — Thu, 06 Jul 2023 09:26:41 GMT

Hi there,

You need a level converter or a resistor to drop the voltage down, as the maximum voltage on the GPIO can be VDD +0V3, where VDD can be anywhere between 1V7 to 3V6,

regards

Jared

RE: Detect Lows and highs and rising falling edges on input pin P21

snoopy20 — Wed, 05 Jul 2023 14:02:38 GMT

Basics -

832 is a 3.6v part, 4.4v will destroy it. You should limit it with a high resistor enough to not damage the protection diodes. 100k should work. If it's a digital input then generally the high signal has to be above Vdd * 0.7, so if you're running 3.6v for Vdd then 2.7v is above the minimum (2.52v), so will be detected.

If the signal has high slew then you may need to consider the comparator.