Interrupts

Using Arduino Project Guidance
#1

What voltages are required to produce an interrupt.0-5 and inbetween? Will an interrupt occur with a 10 millivolt signal? Is the a/d used in the routine or a comparator. If the comparator, the one on the atmega is not available except with a ref of 1.1 volts. Does the interrupt work with the 1.1volt level?

#2

Which interrupt?

#3

Hardware interrupt.

#4

Same as the DC characteristics for inputs …
VIH=0.6VCC
VIL=0.3VCC

#5

So you can go no lower than 300 millivolts? is that 6 v vih? I can live with that. Tnx.

#6

Theres no way to control that is there? Sure wish the comparator was available. Guess I could use pin selected resistor pads to make it somewhat variable.

#7

ATmega48A/PA/88A/PA/168A/PA/328/P Datasheet

For your specific ATmega chip, look up "Typical Characteristics", then "Pin Threshold and Hysteresis". The graphs will show what voltage is read as "1" or "0".

#8

dlloyd:
Same as the DC characteristics for inputs …
VIH=0.6VCC
VIL=0.3VCC

stx38834:
So you can go no lower than 300 millivolts? is that 6 v vih? I can live with that. Tnx.

I think you read it wrong. It’s 0.3 * Vcc == 0.3 * 5V == 1.5V for a 5V Arduino UNO for LOW
and 0.6 * Vcc == 0.6 * 5V == 3V for a 5V Arduino UNO for HIGH.

#9

If the comparator, the one on the atmega is not available except with a ref of 1.1 volts.

Not true.
The analog comparator can produce an interrupt based on a millivolt or less difference between the two inputs AIN0 and AIN1. See the ATmega data sheet for the details, or this post: Gammon Forum : Electronics : Microprocessors : Using the Arduino Analog Comparator

#10

stx38834:
If the comparator, the one on the atmega is not available except with a ref of 1.1 volts.

Nonsense.

#11

stx38834:
Hardware interrupt.

Of course it's a hardware interrupt. Which hardware interrupt?

stx38834:
Sure wish the comparator was available.

Which it is.

#12