// Check the given UsbStream for a valid WireProtocol packet (header). Returns true
// along with the WP_Packet (header) if available. Returns false if nothing valid received as yet.
public static bool ReadPacket(UsbStream stream, out WP_Packet packet)
{
packet = new WP_Packet();
byte[] buffer = new byte[WP_Packet.packetSize]; // Size of marshalled WP_Packet
int nRead;
// Read in enough data for a complete WP_Packet (header)
nRead = stream.Read(buffer, 0, WP_Packet.packetSize);
// If there were not enough bytes to fill the complete WP_Packet, it's no good
if (nRead != WP_Packet.packetSize)
{
return false;
}
// Unmarshal the signature string from the buffer to the WP_Packet
packet.m_signature = "";
for (int i = 0; (i < WP_Packet.m_crcHeader_offset) && (buffer[i] != 0); i++)
{
packet.m_signature += (char)buffer[i];
}
// Unmarshal the rest of the buffer into the WP_Packet structure.
packet.m_crcHeader = ReadUINT32(buffer, WP_Packet.m_crcHeader_offset);
packet.m_crcData = ReadUINT32(buffer, WP_Packet.m_crcData_offset);
packet.m_seq = ReadUINT16(buffer, WP_Packet.m_seq_offset);
packet.m_seqReply = ReadUINT16(buffer, WP_Packet.m_seqReply_offset);
packet.m_flags = ReadUINT32(buffer, WP_Packet.m_flags_offset);
packet.m_size = ReadUINT32(buffer, WP_Packet.m_size_offset);
packet.m_cmd = (Commands)ReadUINT32(buffer, WP_Packet.m_cmd_offset);
// The header CRC must first be zeroed to calculate the correct header CRC
WriteUINT32(buffer, WP_Packet.m_crcHeader_offset, 0);
// If the calculated CRC does not match that of the packet, it is no good
if (packet.m_crcHeader != SUPPORT_ComputeCRC(buffer, 0, WP_Packet.packetSize, 0))
{
return false;
}
return true;
}
// Accepts only a good packet. If the packet is a Ping, the Ping response (ACK) is sent.
// Otherwise, the command is NAK'ed.
static bool RespondToPacket(UsbStream pinger, WireProtocol.WP_Packet inPacket, UInt16 seq)
{
WireProtocol.WP_Packet outPacket = new WireProtocol.WP_Packet();
// Allocate space for any data following the packet
int size = (int)(inPacket.m_size & 0xFFFF);
byte[] buffer = new byte[size];
// Read in the data that came with the packet
if (inPacket.m_size != 0)
pinger.Read(buffer, 0, size);
// Fill in the blanks of the response packet
outPacket.m_signature = "MSdbgV1"; // Standard target signature
outPacket.m_cmd = inPacket.m_cmd; // Show which command this is a response to
outPacket.m_seq = seq++; // Keep track of the target message sequence number
outPacket.m_seqReply = inPacket.m_seq; // Show which host packet sequence number this is a response to
// If the host packet was a Ping
if (inPacket.m_cmd == WireProtocol.Commands.Ping)
{
byte[] data = new byte[8]; // The Ping has an 8 byte data response
outPacket.m_flags = 0x8003; // Return a low-priority ACK
for (int i = 0; i < 8; i++)
data[i] = 0; // Initialize all bytes of the data response to zero
data[0] = 1; // This tells the host that we are TinyBooter
data[4] = 2; // This is an innoccuous flag value
WireProtocol.SendPacket(pinger, outPacket, data); // Send response to the Ping
}
else
{
outPacket.m_flags = 0x4003; // Return a low-priority NACK
WireProtocol.SendPacket(pinger, outPacket, new byte[0]); // Signal to the host that we don't know what to do with the command
}
return true;
}