Senior

Question

Analogue input 40mv out.

7 replies
1177 views

Hi

I am using a stm32L433 100 pin with an external 2.5v reference chip connected to vref+. I have tried placing a voltage (tried different values) onto one of the a/d channel, but the result is 40mv low. I then programmed the D/A , which uses the same VREF+ and tied it to the input channel of the A/D. The value on the D/A is what I expect, but the A/D channel is still reading 40mv too low. Anyone any idea what this may be?

Many Thanks

Scott

This topic has been closed for replies.

waclawek.jan

Super User

Missing or incorrectly performed ADC calibration (e.g. during VREF source startup or violated ADC voltage regulator startup time)? Too high signal impedance plus too short sampling time?

JW

Scott DevAuthor

Senior

As I am using an external VREF (I have connected a 2.5v reference chip), I never done a calibration as I thought it was only for internal VREF?

Thanks

Scott

waclawek.jan

Super User

Okay, and if you stop thinking that?

JW

Scott DevAuthor

Senior

"Okay, and if you stop thinking that?" , what does that mean?

I added the calibration and it worked, I just thought this was for calibrating the internal VREF when not using an external reference.

Thanks

Scott

waclawek.jan

Super User

> "Okay, and if you stop thinking that?" , what does that mean?

That was in reply to your previous:

>> I never done a calibration as I thought it was only for internal VREF

trying to suggest to do calibration which you did and it apparently helped. Please mark thread as resolved.

JW

Scott DevAuthor

Senior

It works well, I simply thought when using internal reference voltage this needed but not when using an external reference voltage

Scott

Scott DevAuthor

Senior

How do you mark the thread resolved?

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