ATTiny85 output to ATMega328p input

Hi!

I'm thinking about connecting an output pin on an ATTiny85 to a an external interrupt pin on the ATMega328p.

Two questions: 1. Thinking about directly connecting the ports and then using OUTPUT mode on the Tiny and INPUT_PULLUP on the 328. Any problems with this setup?

  1. Currently this is one way, Tiny signalling to the 328. If in the future I want to make this bi-directional (i2c for example), would I need an external pull-up resistor between the two?

Thanks!

  1. Connect the GNDs and you are: good to go, Bob's your uncle, hunky dory, voila! (I wonder if there's a Russian equivalent.)

  2. External pull-ups would be a good choice. The internal pull-ups are rather weak.

Have you considered using 1-Wire (bearing in mind the protocol is patented)?

[quote author=Coding Badly link=topic=183445.msg1358989#msg1358989 date=1376951477]1. Connect the GNDs and you are: good to go, Bob's your uncle, hunky dory, voila! (I wonder if there's a Russian equivalent.) 2. External pull-ups would be a good choice. The internal pull-ups are rather weak.[/quote]

Thanks!

Have you considered using 1-Wire (bearing in mind the protocol is patented)?

No.

For my current project, I only need the ATTiny85 to signal a timing event to the 328, no data is communicated. Just pin LOW trigger and done.

Down the road, I would like to simply play with this and possibly implement a simple two way communication protocol for fun. Yes, I said "for fun" :D

Why do you need any pullup? You are connecting an input to an output. The output is either high or low. If the output is never floating or tri-stated pullup is unnecessary. I2C would require pullups.

groundfungus: Why do you need any pullup?

To ensure the line is at a known state until the t85 is ready for business.