I'm a firmware developer more than a hardware designer. I've a doubt about an idea of mine.
I want to obtain serial communication between eight ATtiny85 (slaves) and an ATmega168 (master - It might be also an ATtiny85, but for this question is the same) using only one wire (plus GND).
I'm writting my protocol and it begins to run. I've used the INT0 pin (PB2) of the ATtiny85 and the INT0 (PD2) of the ATmega168; these pins act as digital output when transmitting and, after transmission or as normal behaviour, become/are digital input to receive.
All the MCUs have the same power source, then if two MCUs transmit simultaneously there will be line conflicts and short circuits (if one transmits 1 and an other transmits 0). I want to avoid short circuits!
- Is it the right way to use resistors connected with each single pin limiting the current?
- If I use 9 resistors on the line, one for each pin, do the signal will have stronger attenuation?
At now I will avoid to use active chips other than the MCUs to manage the communications!
The MCUs are each one on a separated circuit, not on the same card, as it may seem in the following picture.
I apologize for the bad pattern, but I have not designed it yet. I have only a small breadboard with just two MCUs now.