# How can I get a 1.1 V reference using analogReference()?

**URL:** <https://forum.arduino.cc/t/how-can-i-get-a-1-1-v-reference-using-analogreference/1180782>\
**Category:** UNO R4 Minima\
**Created:** [October 21, 2023, 7:38pm UTC](https://forum.arduino.cc/t/how-can-i-get-a-1-1-v-reference-using-analogreference/1180782 "2023-10-21T19:38:23Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![sarojmoh324](https://avatars.discourse-cdn.com/v4/letter/s/d26b3c/32.png) [@sarojmoh324](https://forum.arduino.cc/u/sarojmoh324)\
**Post date:** [October 21, 2023, 7:38pm UTC](https://forum.arduino.cc/t/how-can-i-get-a-1-1-v-reference-using-analogreference/1180782/1 "2023-10-21T19:38:23Z")

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Hi!

I just got a R4 minima and want to use 1.1v for `analogReference`.

I've read this thread several times but don't understand the solution you came up with:

> [@readVcc function using new UNO R4 RA4M1 ADC](https://forum.arduino.cc/t/readvcc-function-using-new-uno-r4-ra4m1-adc/1150116):
>
> Hi everyone, Fairly new to Arduino (month or two), very new to the forum as an active user (first post). I have been using the code below (picked it up somewhere (unfortunately, cannot recall original source, have seen it come back in several places) along the many forum posts and/or YouTube tutorials, for reading analog sensors on Arduino UNO R3 (8-bit ATmega328P) and added my own comments to better understand what is going on. This code is a function, used to read the actual supply voltage Vc…

I copied the override to the `readVcc` function provided in [**this post**](https://forum.arduino.cc/t/readvcc-function-using-new-uno-r4-ra4m1-adc/1150116/19). However, I get `intVREF1` is not defined.

How did you get this working? Is the only other solution to use external Aref and then provide a 1.1v source? Thanks!

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**Author:** ![fdw\_arduino](https://avatars.discourse-cdn.com/v4/letter/f/ed655f/32.png) [@fdw\_arduino](https://forum.arduino.cc/u/fdw_arduino)\
**Post date:** [November 5, 2023, 8:25pm UTC](https://forum.arduino.cc/t/how-can-i-get-a-1-1-v-reference-using-analogreference/1180782/2 "2023-11-05T20:25:24Z")

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Hi, sorry for the late response. Forum update mail went straight to spam.  
I have never used an external Aref myself so cannot help on that. I was trying to update the readVcc function used with R3 using the internal 1.1V ref to R4.  
I do not know how/where you have defined/tried to define your intVREF1 variable, but in my case, intVREF is a global float that holds my fixed/accurate value for the 1.1 internal ref voltage (+stored in device EEPROM) when I am using an R3 and another correction factor around 1 if using an R4. So for the function to work, you will have to define this variable yourself outside the scope of this function.