PCB revision is v1.4, LDO IC maybe U56 (not so good readable). PA20 logical levels can be test with the following: echo "20" > /sys/class/gpio/export echo "out" > /sys/class/gpio/gpio20/direction echo "1" > /sys/class/gpio/gpio20/value and echo "0" > /sys/class/gpio/gpio20/value
Hi All, On new revision of Orange Pi Zero (512M) board, chinsee engineers changed the PCB by removed the R66/R69 resistors (PA20 / Wifi power logical pull up). As I measured on board the PA20 line can be accessed on pin of XR819 power supply LDO (5V/1.8V). The U58 IC pin3 (marked on photo) should be elevate from PCB and should pull up to 3.3V logical "1" level. The PA20 line for I2S data out is accessed from pcb pin. Good luck!