Is there a way to find out edge polarity in an interrupt without a re-read? STM32H750

[VN.2]

Hi, I have both rising and falling edge enabled for an EXTI interrupt on GPIO. I would like to know what edge the interrupt has been entered on, re-reading the GPIO line is error prone and not viable due to latency. I can have a counter that I check with "c & 1", but I'm worried about the initial state of the line which is unknown, this could break the "c & 1" logic.

Is there a correct way to find out the interrupt polarity, without additional reads of the interrupt line?

[Tesla DeLorean]

If you've got signals this flaky externally, buffer them.

Or use a TIM pin where the CH1 / CH2 trigger on upposing edges of the TIMx_CH1 input pin (CH2 can use via Indirect Mode, ie criss-cross of CH1<->CH2, and CH3<->CH4)

[VN.2]

Thanks for the answer. The signal integrity is pretty good and not noisy, the edges are coming in pretty quick tho, rising edge followed by falling happens in a 16ns timespan. I need to decide if I need to change the MODE of both PortA and B. If another falling edge comes in I can keep MODE the same, if not I need to change it. I want to prevent reading GPIO pins because that adds about 40ns delay. The signal stays low for about 200ns in that time I also have to read ram and output to PortA and B. Unfortunately I can't use DMA to output on PortB as pin[0..3;9..12] of the B port are not accessible and I need to workaround that by having the CM7 shift the data. If there is some way to shift by 4 through DMA which I missed it would be awesome!

[Tesla DeLorean]

Definitely seems like something to be done via a CPLD and/or logic directly

Consider using BSRR rather than ODR if you need to scatter-shot a subset of GPIO within the bank

Things like FIFO memories can provide elasticity where there is some mismatch of rates, or burst behaviours.

[AScha.3]

or...connect input to 2 exti pins, set one to rising and other to falling edge.

then dont need to read state after trigger. 🙂

[VN.2]

Makes sense if you have pins to spare 🙂 Unfortunately not a possibility for me.

[Tesla DeLorean]

A TIM should be able to cross​ connect one pin to two channels via indirect mode.

[VN.2]

What is a TIM and how much added latency are we talking about?

[AScha.3]

TIM -> timer