Stm32f429 disc1

[harry123]

Hi

Im using Stm32f429 disc1 board internal adc im using the signal generator and giving constant input but the waveform after plotting gives variation for each trail.

[TDK]

Seems like a reasonable signal to me.

ADC values will not be exact, expect some amount of noise. See here for general tips to improve ADC accuracy:

https://www.st.com/resource/en/application_note/an2834-how-to-optimize-the-adc-accuracy-in-the-stm32-mcus-stmicroelectronics.pdf

https://www.st.com/resource/en/application_note/an4073-how-to-improve-adc-accuracy-when-using-stm32f2xx-and-stm32f4xx-microcontrollers-stmicroelectronics.pdf

[harry123]

The input signal is shifting as soon as I connect to my stm32f429 board 

[TDK]

Add more details here if you want a more specific response. What are the blue and red lines? What are you expecting them to look like and why? What does shifting mean? You say constant input, but your output looks like a wave? How is signal being generated?

[harry123]

1)A sine wave  from the function generator when checked through oscilloscope before and after connecting to input of stm giving me little shift (before converting)

2)The red and blue line are output waveform after converting the adc sample.

3)I'm not able to find out where I'm going wrong

I want a fixed output whenever I measure

[TDK · Accepted solution]

The ADC will load the signal to some degree. It acts like a ~50 kOhm load. If your signal generator is in high impedance mode, this will affect the signal. Probably that is the issue.

Solutions:

• Use a better signal generator that can drive lower impedance modes.
• Buffer the signal generator output with a voltage follower or other op-amp solution with high input impedance.