I’am using AB-02A and need software serial to work. Using GPIO2 for RX from the example doesn’t work for me because it doesn’t set to high at initialization. Changing mode to INPUT_PULLUP didn’t change status. Replace GPIO2 with GPIO8, everything works. My guess is that work because GPIO8 is also SCL1, so it must have internal pull-up resistor.
My question is would AB-01 work? I doesn’t have connection on the board for the GPIO8, so must use some other GPIO.
softSerial RX pin high
You can refer to this original picture to choose the pin you need.