Question about the STM32F429 board

[tasabao]

Hi, I'm having some problems with the STM32F429 DAC testing. I have two boards of the same type. On board 1, the Digital Storage Oscilloscope shows that the sine wave voltage ranges from 2.08V to 2.94V. However, on board 2, with the same program and settings, the output voltage ranges from 0V to 3V (which is the correct output I need). Please help me figure out why there is a difference between the two boards.

The output on the left is correct, and I'm only using the PA4 pin for the sine wave test without any additional output circuit. 

Thanks everyone.

[MM..1]

Simply check PA4 in schematics . Disco boards have many connected periph...

[AScha.3]

Hi,

> I'm only using the PA4 pin

-- but PA4 is used on board :

and has pullup:

So maybe it depends on the behavior of the TFT , what PA4 doing as dac output.

-- You could try : PA5 , dac-out2 -- seems to be unused on disco 

 

[tasabao]

Thanks for the answer its correct now, want ask another question. So the PA4 can't do the same thing like PA5?

Thanks!

[AScha.3]

Good.

And PA4 can do the same thing like PA5 - but not on this board, because on PA4 the LCD is connected;

so PA4 is not "free" /unused here .

see circuit of your board:

https://www.st.com/resource/en/schematic_pack/mb1075-f429i-e01_schematic.pdf