Hello,
I'm connecting a SparkFun OBD-II UART to a SparkFun RedBoard ATP. I'm noticing that the RedBoard has "3.3V MAX" written all over it, the max for all pin connections (after I start testing connections yikes hah!).
The part I'm having trouble deciphering is the voltage exiting the OBD-II UART TX-0 and RX-1 pins. Is it 5v or 3.3v? I'm seeing both listed in the schematics. It's making my vision blur at current alertness and experience level. :o
Thanks in advance for helping me take a look!
Have you looked through the hookup guide OBD II UART Hookup Guide - SparkFun Learn?
Hey there, sure thing. The RedBoard and Arduino mentioned there accept 5v I think.* (different than the Artemis ATP). It also mentions that the UART board regulates for both 3.3v and 5v:
The STN1110 is the main controller chip on the board. This communicates with the CAN, ISO and J1850 transceivers. Voltage on the board is regulated to both 5V and 3.3V for all of the components to function properly. The board is powered from the DB9 connector.
I wasn't quite sure how that applied to UART outbound RX pin.
Giving it a shot:
I believe the pins I connect to are here:

It's on the sheet titled, 3.3+v Power Supply along with other components on the page.
However, it seems to lead here:

I see 5V there... with a strong looking resistor in between. So, it could be 3.3v (actually, it's getting late, I'm worried about RX yes)? (looking up the resistor now...)
And THEN there's this tutorial. It says I need a logic level converter. However, I feel I should check it and know how to check it since I'm here in this thread. 


The resistor looks more like a pullup than a voltage divider. All the references I have seen are about hooking the device up to an Arduino. I did not find any references to hooking the device up to an ESP32. Me, I'd say the device is a 5V and go from there.
Cool. I'm happy with that answer.
Thanks for taking a look!