Livt.Usb

src/packets/PacketPid.lvt

namespace Livt.Usb.Packets

/**
 * USB low/full-speed packet identifiers including their complemented upper nibble.
 * Only the directly attached control/interrupt/bulk profile is admitted here.
 */
component PacketPid
{
	public const OUT: byte = 0xE1
	public const IN: byte = 0x69
	public const SETUP: byte = 0x2D
	public const SOF: byte = 0xA5
	public const DATA0: byte = 0xC3
	public const DATA1: byte = 0x4B
	public const ACK: byte = 0xD2
	public const NAK: byte = 0x5A
	public const STALL: byte = 0x1E

	/**
	 * Checks the PID's redundant nibble separately from supported packet kinds.
	 */
	public static fn IsValid[](pid: byte) bool
	{
		return (((pid as uint) ^ ((pid as uint) >> 4)) & 0x0F) == 0x0F
	}

	/**
	 * Tokens and SOF carry eleven information bits plus CRC5.
	 */
	public static fn IsToken[](pid: byte) bool
	{
		return pid == OUT || pid == IN || pid == SETUP || pid == SOF
	}

	/**
	 * DATA0 and DATA1 carry payload followed by CRC16.
	 */
	public static fn IsData[](pid: byte) bool
	{
		return pid == DATA0 || pid == DATA1
	}

	/**
	 * Handshakes end immediately after PID.
	 */
	public static fn IsHandshake[](pid: byte) bool
	{
		return pid == ACK || pid == NAK || pid == STALL
	}
}