SPINEL_PROP_GPIO_CONFIG value

GPIO Configuration Format: `A(CCU)` Type: Read-Only (Optionally Read-write using `CMD_PROP_VALUE_INSERT`) An array of structures which contain the following fields: * `C`: GPIO Number * `C`: GPIO Configuration Flags * `U`: Human-readable GPIO name GPIOs which do not have a corresponding entry are not supported. The configuration parameter contains the configuration flags for the GPIO: 0 1 2 3 4 5 6 7 +---+---+---+---+---+---+---+---+ |DIR|PUP|PDN|TRIGGER| RESERVED | +---+---+---+---+---+---+---+---+ |O/D| +---+ * `DIR`: Pin direction. Clear (0) for input, set (1) for output. * `PUP`: Pull-up enabled flag. * `PDN`/`O/D`: Flag meaning depends on pin direction: * Input: Pull-down enabled. * Output: Output is an open-drain. * `TRIGGER`: Enumeration describing how pin changes generate asynchronous notification commands (TBD) from the NCP to the host. * 0: Feature disabled for this pin * 1: Trigger on falling edge * 2: Trigger on rising edge * 3: Trigger on level change * `RESERVED`: Bits reserved for future use. Always cleared to zero and ignored when read. As an optional feature, the configuration of individual pins may be modified using the `CMD_PROP_VALUE_INSERT` command. Only the GPIO number and flags fields MUST be present, the GPIO name (if present) would be ignored. This command can only be used to modify the configuration of GPIOs which are already exposed---it cannot be used by the host to add additional GPIOs.