This article provides instructions on how to test the GPIO on Elo's Backpack for Android devices
Using GPIO Cable Kit: P/N: E211544 or similar cable. Launch the ELO Peripheral Test app and insert the GPIO cable into the GPIO connection on the Backpack 4.0 device.
a. Short the white line with black line. == GPIO81 should become Low
b. Short the Green line with black line. == GPIO82 should become Low
c. Measure the voltage of Red line== It should be 5V
d. Change GPIO80 output to Low. It should become 0 V
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