nrf5340 adc with internal reference

RE: nrf5340 adc with internal reference

Kenneth — Mon, 11 Jul 2022 09:11:32 GMT

1. Try to add the capacitor I mentioned on the analog inputs you are using.

2. You should configure CH[] registers in the order you want to sample the analog input, for instance you can:

CH[0] = analog input 1
CH[1] = analog input 0
CH[2] = analog input 6

Please see that there is no direct relation between CH[n] and analog input m.

Best regards,
Kenneth

RE: nrf5340 adc with internal reference

MaximSh — Sun, 10 Jul 2022 09:31:26 GMT

1. After the increase of the Acquisition time it is not working. looks like 40us is not enough for 1.5MOhm Resistor.
2. when i set bits in adc_sequence channel, the samples to the output buffer written by setup sequence of channels or by channels order? for example setup for channel setup sequence channel_1,channel_0,channel_6 -> buffer={channel_1,channel_0,channel_6} or buffer={channel_0,channel_1,channel_6}

RE: nrf5340 adc with internal reference

Kenneth — Fri, 08 Jul 2022 10:02:23 GMT

1. This should work yes.

2. You may either considering adding a small capacitor (e.g. 10nF) in series with R2 (this capacitor will charge the internal sampling capacitor when performing an ADC measurement) , or alternatively you can increase acqusition time, you can find a table that show acquisition time as function of source resistance:
https://infocenter.nordicsemi.com/topic/ps_nrf5340/saadc.html#concept_qh3_spp_qr

Best regards,
Kenneth