Interfacing with adafruit breakout for maxim 31850 one wire thermocouple amp

[amateur_25]

Hi,
After waiting eagerly for my amp to arrive and paying for next day courier delivery, I'm disappointed I still need a level shifter.
I wasn't aware of this until I read the wire test tutorial on adafruit website after it had arrived DOH.

My understanding is I need a bidirectional Level shifter therefore a simple resistive divider wont do. ON sparkfun website it shows BSS138 MOSFET being used to as a bidirectional level shifter however it's not easy for me to get parts in Manchester.  Can I use a BS170 instead? Any help would be greatly appreciated!!
https://learn.sparkfun.com/tutorials/bi-directional-logic-level-converter-hookup-guide

Alternatively can not just power the atmega328 chip using 3.3v then I don't need to level shift right?

[Zero999]

It won't work very well. The BS170 has a higher threshold voltage than the BSS138.

See the app note where they got the circuit from for more information.

http://dlnmh9ip6v2uc.cloudfront.net/tutorialimages/BD-LogicLevelConverter/an97055.pdf