Step Signals at The Conversion Output of The ADC

[AE104]

Hello,

I use internal ADC of the STM32F767 microprocessor. When I plot the converted data in the Excel, I see a step signals initially. But when I check the analog signal input of the ADC with oscilloscope, there is no signal as step signals initially. Does anyone have an idea about why there is a signal like this?

In the picture, I circled with a red of the problem.

Thank you,

[Uwe Bonnes]

There are many things to consider when converting analog signal. You do not tell of any measure you have taken, so anything is guessing. Learn about input impedance, sampling time and much more....

[AE104]

After the end of the step signal, the converted signal is true. I can share what information you need.

[AE104]

Also when I enable the DMA continuous request, there is no step signal initially. But in this case I couldn't catch the signal properly. When I disable the DMA continous request mode, I catch the signal but there is a step signal initially like in the first post.

[waclawek.jan]

What do you exactly mean by "initially"?

VDDA/VREF unstable?

JW

[Ozone]

> But when I check the analog signal input of the ADC with oscilloscope, there is no signal as step signals initially.

How did the corresonding input signal(s) look like ?

First, apply a known DC voltage to the ADC input and check the ADC results.

Then, apply a reference signal of a frequency relevant for you application, and check the ADC results.