What should I pay attention to when using SADC?

[Hansome]

I use nrf_drv_saadc_init(NULL, NULL) to sample AD per second(Blocking type).

But every time the firmware runs, the ADC value always takes several times to stabilize.

Ready!
Battery 0 voltage = 40, ADC = 66
Battery 0 voltage = 82, ADC = 133
Battery 0 voltage = 124, ADC = 201
Battery 0 voltage = 165, ADC = 268
Battery 0 voltage = 207, ADC = 335
Battery 0 voltage = 248, ADC = 402
Battery 0 voltage = 291, ADC = 470
Battery 0 voltage = 332, ADC = 537
Battery 0 voltage = 332, ADC = 537
Battery 0 voltage = 333, ADC = 538
Battery 0 voltage = 333, ADC = 538
Battery 0 voltage = 333, ADC = 538
Battery 0 voltage = 333, ADC = 538
Battery 0 voltage = 333, ADC = 538

What should I pay attention to when using SADC? Thanks!

[AndreasF]

Hello, Hansome.

Have you checked that you have the correct pin mapping? Could you post it? Have you checked that you don't have any floating pins?

Best regards,

Andreas

[Hansome]

There is no problem with pin configuration. You see, the last ADC values are all right, but there's an incremental process ahead that's confusing.

[AndreasF]

Hi again.

How are you handling the external crystal? Do you start it and immediately start sampling?

Have you measured the pin with a scope or a similar thing?

Do you have something else using the pin before saadc_init()?

Best regards,

Andreas