# Reference voltage control for the ADC

**URL:** <https://community.particle.io/t/reference-voltage-control-for-the-adc/5971>\
**Category:** uncategorized\
**Created:** [July 25, 2014, 8:55am UTC](https://community.particle.io/t/reference-voltage-control-for-the-adc/5971 "2014-07-25T08:55:23Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![miska](https://avatars.discourse-cdn.com/v4/letter/m/e99b99/32.png) [@miska](https://community.particle.io/u/miska)\
**Post date:** [July 25, 2014, 8:55am UTC](https://community.particle.io/t/reference-voltage-control-for-the-adc/5971/1 "2014-07-25T08:55:24Z")

</div>

Is there any way to control the voltage reference for the ADC in the spark core? I have some signal wander in positive and negative domains.

---

<div class="post-metadata">

**Author:** ![bko](https://sea2.discourse-cdn.com/flex026/user_avatar/community.particle.io/bko/32/20704_2.png) [@bko](https://community.particle.io/u/bko)\
**Post date:** [July 25, 2014, 1:24pm UTC](https://community.particle.io/t/reference-voltage-control-for-the-adc/5971/2 "2014-07-25T13:24:25Z")

</div>

Hi @miska

The reference voltage for the ADC is tied to a filtered version of 3.3V and is not changeable. The STM32 ARM does not allow negative voltages anyway.

You have two choices:

- You can add an op-amp or two to do signal scaling and center the range on 1.65V
- You could try AC coupling the input with clamping diodes.

Can you say more about the signal you are measuring? Fast? Slow? What voltage range?