I would think that pull-ups / pulldown resistors are disabled (SAMV71, ASF4) when an Analog function is selected for an ADC pin. However, I can’t find anything in the data sheet that says that. And I want them off.
I have an analog input pin with a voltage divider (100k, 100k) on the input so with a 3.3Volt input I would expect to see 1.65 volts coming to the ADC. I read 2.14 Volts. A Voltmeter confirms that there is 2.14V on the divider. There resistors appear to be correct.
The HW engineer believes that there is an internal pullup on the ADC internally causing the voltage change. I would think that pull-ups are disabled when Analog mode is selected. But I can’t find confirmation in the V71 datasheet.
Atmel Start does not have any way to select a pullup on an analog pin. I can’t find any call the PIO_PUER (Pulldown Enable Register) for that pin in the generated startup code. Using my IAR debugger, the PIO_PUSR (Pullup Status Register) is a ‘1’ for that bit, which would indicate pullup is disabled, unless this bit is invalid when in Analog mode.
Can anyone confirm that pull-ups/pulldowns are disabled in Analog mode?