how much trigger voltages for STM32F103 rising falling edge triggered interrupts are?

0
votes

I'm a little confused about the trigger voltage for rising-falling triggered interrupts. As my previous understanding, the trigger voltage should be Vih and Vil. But some one told me Vih and Vil is not for edge triggered interrupts. The thing is, when I observe the waveform with a Oscilloscope along with an interrupt counter from Keil, I did see the interrupt happened when the voltage did not reach the Vih(rising edge). I use 3.3V voltage. The signal is only 1V around and the interrupts was triggered. I checked the manual of STM32 and did not find the answer.

Could some one help?

Thanks,

1
stm32interrupt
I don't understand how you reach your conclusion. How can you know exactly when the interrupt was triggered ? - Guillaume Petitjean
Hi, st-link is connected to our test board with J-TAG. So I can see the counter change when interrupt happened, along with waveform in oscilloscope. - yebii
OK but how do you know exactly what voltage level triggered the interrupt ? - Guillaume Petitjean
Hi, I do not need to know which voltage level triggered interrupt. What I can see is the peak voltage is around 1 volt. So I feel really confused. - yebii

1 Answers

1
votes

The levels are the same whether you are using an interrupt or polling.

VIH min is the minimum voltage that is guaranteed to be interpreted as a high, and VIL max is the maximum input that is guaranteed to be interpreted as a low.

Any voltage between these two levels could be interpreted either way.

As well as that, there isn't a single changeover voltage because the inputs have schmitt triggers with at least 200mV of hysteresis.

To guarantee to not trigger the rising edge you need to stay below VIL max, which at 3.3V is 1.155V.