# For Qwiic 12-Bit ADC, what do these terms mean?

**URL:** <https://community.sparkfun.com/t/for-qwiic-12-bit-adc-what-do-these-terms-mean/68086>\
**Category:** Sensors\
**Created:** [February 17, 2026, 9:32pm UTC](https://community.sparkfun.com/t/for-qwiic-12-bit-adc-what-do-these-terms-mean/68086 "2026-02-17T21:32:59Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![benjamingslade](https://yyz1.discourse-cdn.com/sparkfun/user_avatar/community.sparkfun.com/benjamingslade/32/8461_2.png) [@benjamingslade](https://community.sparkfun.com/u/benjamingslade)\
**Post date:** [February 17, 2026, 9:32pm UTC](https://community.sparkfun.com/t/for-qwiic-12-bit-adc-what-do-these-terms-mean/68086/1 "2026-02-17T21:32:59Z")

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Looking at:

> **[Qwiic 12-Bit ADC Hookup Guide - SparkFun Learn](https://learn.sparkfun.com/tutorials/qwiic-12-bit-adc-hookup-guide/hardware-overview)**

What do the following things mean:

- “3.3V breakout pin” - There is no breakout pin like this on the picture of the board
- VDD - No pin or connector on the board says “VDD”
- VCC - Is this an input or output? Is this the same as “VDD”

Can I have this board work off of 5v, but still talk on the I2C bus? (I’m guessing “yes” because the master only has pullup resistors on the bus?? All other nodes are pulldown transisters only?)

Thanks in advance  
Ben

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**Author:** ![jremington](https://yyz1.discourse-cdn.com/sparkfun/user_avatar/community.sparkfun.com/jremington/32/6595_2.png) [@jremington](https://community.sparkfun.com/u/jremington)\
**Post date:** [February 17, 2026, 10:17pm UTC](https://community.sparkfun.com/t/for-qwiic-12-bit-adc-what-do-these-terms-mean/68086/2 "2026-02-17T22:17:35Z")

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> [@benjamingslade](#):
>
> Can I have this board work off of 5v,

Not when using the Qwiic connector with the MCU. 3.3V is supplied by the connector, and you can measure voltages only between 0 and 3.3V.

The terms Vcc and Vdd are equivalent. They can be power in or out, depending on the particular module or MCU.

Which MCU board do you intend to use?

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<div class="post-metadata">

**Author:** ![benjamingslade](https://yyz1.discourse-cdn.com/sparkfun/user_avatar/community.sparkfun.com/benjamingslade/32/8461_2.png) [@benjamingslade](https://community.sparkfun.com/u/benjamingslade)\
**Post date:** [February 18, 2026, 12:32am UTC](https://community.sparkfun.com/t/for-qwiic-12-bit-adc-what-do-these-terms-mean/68086/3 "2026-02-18T00:32:09Z")

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Not sure what MCU stands for, but I was thinking about using this ADC with the [SparkFun IoT RedBoard - ESP32](https://www.sparkfun.com/sparkfun-iot-redboard-esp32-micropython-development-board.html) On the other hand, might just use the lower accuracy on-the-RedBoard ADC with a voltage divider made from 2 resistors between the 5v pin and ground.

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<div class="post-metadata">

**Author:** ![jremington](https://yyz1.discourse-cdn.com/sparkfun/user_avatar/community.sparkfun.com/jremington/32/6595_2.png) [@jremington](https://community.sparkfun.com/u/jremington)\
**Post date:** [February 18, 2026, 1:03am UTC](https://community.sparkfun.com/t/for-qwiic-12-bit-adc-what-do-these-terms-mean/68086/4 "2026-02-18T01:03:14Z")

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MCU = microcontroller unit. The Sparkfun IoT Redboard ESP32 is an example of an MCU board.

The ESP32 is a 3.3V processor, so just use the Qwiic connector and cable to connect with the ADC board.

Voltage input to the ADC must be within the range of 0V to 3.3V or the ADC will instantly be destroyed.

Note: the ADC built into the ESP32 processor chip is nonlinear, inaccurate and not very useful for making quantitative voltage measurements.