Timeline for When does the ADC start reading again in interupt mode?

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Jun 6, 2020 at 22:17	comment	added	Edgar Bonet		@BeaconofWierd: I agree with Sim Son that the resistance is too high. According to the datasheet, the ADC should be fed the voltage to be measured from a source with no more than 10 kΩ of internal impedance.
Jun 6, 2020 at 22:06	comment	added	Sim Son		@BeaconofWierd that's probably your circuit catchinh some electromagbetic radiation and 300kOhm is simply too high to pull the analog pin to ground in that case. If you imagine you increase this resistance, at some point you would consider the pin floating (maybe at 1MOhm or at 100MOhm?).
Jun 6, 2020 at 20:35	comment	added	Beacon of Wierd		Thanks for the clarification :) Quick unrelated question (if you don’t know the answer I’ll delete this comment). In some debugging efforts I hooked up the A0 pin I was reading from to ground with a 300k resistor between them and got some rather significant ( up to 20 ) readings from it, fluctuating like a wave. I would expect it to be 0, what exactly is being measured when doing this? I thought the ADC did not recieve any voltage inside itself so where is the voltage comming from? :s guessing this is related to "floating pin readings", but I am still confused.
Jun 6, 2020 at 16:25	history	answered	Edgar Bonet	CC BY-SA 4.0