REN
if (gpiod_get_value(REN) == 0)
gpios_vector[&(REN) - &all_descriptors[0]] = 0; /* 27 -> 0 REN on GPIB pin 0 */
gpiod_direction_output(REN, 1);
gpiod_direction_output(REN, 1); /* user space must enable REN if needed */
gpiod_direction_output(REN, 0);
gpiod_direction_output(REN, 1);