I have a setup as seen in this image:
The question is what will the voltage at the line on the left size (marked with [Volt ??] ) be when the open-drain logic is active? The goal is to have a logic zero but I am not sure how the diode D1 is going to affect this. Will it depend of its forward voltage or some other characteristics? How can I estimate the voltage at [Volt??] to make sure it will be low enough to register as logic zero?
- For clarifications: this is an I2C bus connecting a Raspberry Pi to an Atmel ATTiny13 micro-controller. The 3.3v and R1 are the RPi side, and the open-drain side is one of the ATTiny I/O pins. The diode D1 is added to protect the RPi from miss configuration on the ATTiny side that might pull the line high to 5v which might damage the RPi.