RE: SAADC buffer / UART data noise problem questions

Einar Thorsrud — Tue, 13 Oct 2020 13:31:49 GMT

Hi Yclee,

[quote user=""]So, I changed the code like below and I can see the 0 value in LOG info.[/quote]

Can you upload your code from Insert -> Code instead of screenshots? That would make it more readable. Please also note that you getting negative values indicate that the SAADC has not been calibrated. I recommend you consider using the internal reference instead of VDD/4, and that you perform calibration at startup.

[quote user=""]1) p_event->data.done.p_buffer[0] = 0; this line code cannot be changed the pointer value?[/quote]

Can you clarify? What this line does is take the first element in the p_buffer array and sets the value to 0, but I am not sure what was the question?

[quote user=""]2) Is is right method that 1channel and 1buffer using?[/quote]

I do not see any obvious issues, but it depends on what you want. Is there an issue here?

But you are right that there will be noise in any case. This is why you may want to consider oversampling, which is basically taking a number of samples and averaging them. As you use VDD as reference you may get noise depending on the current draw from the nRF (as it may cause voltage to drop). So seeing noise based on UART activity or other is not unexpected in this case.