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Unknow source of Noise on SAADC input

Hello,

I need to read resistive sensors values with SAADC. These sensors going throught multiplexer and amplifier.
Infortunaly, the signal going into the SAADC is noisy. It seems to be radio event, but when i use a radio_notification flag, the noise is'nt synchronized with the radio ON/OFF events. I'm sure my sensors acts as an antenna, but i can't find the source of this noise. Any idea?

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  • It seems that the noise comes directly from sensors, as i was thinking, my resistive pannel act as antenna. If i disconnect P0.03 from the amplifier output, it's the same problem. Vcc is also clean. 

    I have already done this hardware with other dev boards (not BLE), and i never had this kind of noise before, it's why i was thinking about radio interference. 

    The picture of the zoomed noise looks like radiated frequency modulation to me, more than a capacitive coupling of high speed digital tracks. But, the frequency of noise is about 1 MHz, so i don't know where this comes from (my probe is not RF, but the bandwith is supposed to be 25MHz).

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