# How to combine 5V-powered ATmega16A and MAX44009? [duplicate]

I'm programming my ATmega16A through LPT port using uisp -dprog=bsd. Although ATmega16A supports $$\V_{CC}=2.7\,\mathrm V\,..\,5.5\,\mathrm V\$$, to make logical levels compatible with LPT port, I have to supply 5V to the ATmega.

All works fine, but now I need to connect MAX44009 lux meter (working via I²C) to the controller. MAX44009 supports $$\V_{CC}=1.7\,\mathrm V\,..\,3.6\,\mathrm V\$$, which appears too low to safely input 5V to it.

For transmitting data I could use e.g. a voltage divider to supply a fraction of 5V to MAX44009, and pull-up the SDA and SCL lines to this power source. Since SDA & SCL are open drain, this would work fine as far as we're only driving MAX44009's input. But when we want to read data back, we have a problem: 3.6V doesn't seem to be good enough to be seen as high level input for 5V-powered ATmega.

So, how can I actually safely connect ATmega16A to MAX44009, without losing the ability to program ATmega via LPT port? Some web pages like this one simply suggest powering MAX44009 with 5V without explaining why. Others like this one say that working voltage is 3 ~ 5 V, which also looks strange.