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there is no external voltage applied on those pins P14,P15,P16,P17 , Its just floating connected from IO expander to header connector.
We are trying to achieve a loopback on those four pins on connector using cable or wire , loopback between the P15 to P17 , P14 to P16 . these pins are just GPIOs.
Driving the pin P15 as high or low as output configuration and reading from P17 as input configuration , same reverse also checking from pin P17 as output , P15 as input.
Driving the pin P14 as high or low as output configuration and reading from P16 as input configuration , same reverse also checking from pin P16 as output , P14 as input.
