3.3V powered ESP8266 and 5V ADC

Projects Networking, Protocols, and Devices
1

Hello guys,

I am trying to hook an ADS1115 powered with 5V and measuring 5V on A0 to an ESP8266 powered with 3.3V.

Thought about using a res divider on SDA and SCL for that purpose (with 1k and 2k resistors) but what voltage I get then is around 0.77V.

I think there is something I don't get about I2C because if I use the same res divider straight on the 5V (power supply) I do get ~3.3V.

Should I be using a logic level converter? Should I be hooking SDA and SCL straight to the ESP even if I a measuring 5V on their pins?

Thank you

2

Why are you trying to run the ADS1115 at 5V?

res divider on SDA and SCL... something I don't get about I2C.

welp, that is some good hedging, my fortune cookie says "you are destined for greatness".

3

Depends on the sensor. Post a link.
Makes generally speaking more sense to power the ADS1115 from the same supply as the ESP, and drop the voltage that you want to measure with a voltage divider to the level that the ADS can work with (e.g. 2.048volt, PGA 2).
Leo..

4

@ron_sutherland because I want to measure 5V on A0 and difference between VDD and analog inputs can't be higher than 0.5V I think (would have to check data sheet).

@Wawa ok that sounds like something I could do, will give it a try.

Thank you