Hi ,   I am finding trouble using orange pi gpios, here my approach I am trying to scan 4x4 kepad using gpio how am I writing 0 to a particular gpio pin?   step 1 :  sunxi_gpio_set_cfgpin(pin, SUNXI_GPIO_OUTPUT);   step 2: sunxi_gpio_pullup(pin ,SUNXI_PULL_DOWN);   I am not sure whether I am correct here. I am not sure if I have to use UP or DOWN or NONE here in pull up call,but I tried UP and DOWN so for.   step 3: