I am using the ATMEGA1284P in our project
To be able to detect incoming SMS event from a modem while in SLEEP_MODE_PWR_DOWN. I change the behaviour of the RX pin from UART config to PCINT.
This works fine in many cases, but unfortunatly not always.
What I have discovered by measuring this with a scop is that the PCINT is not detecting edges as quick As i want it to.
If the UART stream is to short the PCINT interrupt is not able to detect the signal changes. It seems like it need up to 11 mS.
So with the short prefered URC msg I am not able to detct it.
With a longer URC which contain the hole SMS msg I am able to detect it. Unfortunatly configuring with this URC will not enable the modem to store it in the modems internal memory for later on readout to parse what the SMS info actual is.
So my main question is, is it correct that a PCINT interrupt has some kind of latency during POWER DOWN SLEEP?