public int[] getPacket(byte[] someFileArray) {
boolean gotAPacket = false; // whether the first byte was 0x7E
int packetLength = -1; // length of the dataArray
int[] thisdataArray = null; // the dataArray to return
int checksum = -1; // the checksum as received
int localChecksum = -1; // the chacksum as we calculate it
if (DEBUG) System.out.println("fileIndex: " + fileIndex);
if (DEBUG) System.out.println("file length: " + fileArray.length);
// make sure you have a 0x7E and at least three bytes
if (getNextByte() == 0x7E && fileArray.length > 2) {
gotAPacket = true;
}
// if the header byte is good, try the rest:
if (gotAPacket) {
// read two bytes
if (bytesAvailable() >= 2) {
int lengthMSB = getNextByte(); // high byte for length of packet
int lengthLSB = getNextByte(); // low byte for length of packet
// convert to length value
packetLength = (lengthLSB + (lengthMSB << 8));
if (DEBUG) System.out.println("length: " + packetLength);
}
// read bytes until you've reached the length
if (bytesAvailable() >= packetLength && packetLength > 0) {
// make an array to hold the data frame:
thisdataArray = new int[packetLength];
// read all the bytes except the last one into the dataArray array:
for (int thisByte = 0; thisByte < packetLength; thisByte++) {
thisdataArray[thisByte] = getNextByte();
if (DEBUG) System.out.print(parent.hex(thisdataArray[thisByte], 2) + " ");
}
if (bytesAvailable() >= 1) {
// get the checksum:
checksum = getNextByte();
}
// calculate the checksum of the received dataArray:
localChecksum = checkSum(thisdataArray);
// if they're not the same, we have bad data:
if (localChecksum != checksum) {
if (DEBUG) System.out.println("bad checksum. Local: " + parent.hex(localChecksum % 256));
if (DEBUG) System.out.println(" remote: " + parent.hex(checksum));
// if the checksums don't add up, clear the dataArray array:
thisdataArray = null;
}
}
}
// makes a nice printing for debugging:
if (DEBUG) System.out.println();
// return the data frame. If it's null, you got a bad packet.
return thisdataArray;
}
public void sendPacket(int[] thisFrame) {
// calculate the length of the total array
// header byte + length (2 bytes) + command + checksum:
int packetLength = thisFrame.length + 4;
// set up the array you'll actually send:
int[] packet = new int[packetLength];
packet[0] = 0x7E;
// get the high byte and the low byte of the length of the frame:
packet[1] = thisFrame.length / 256;
packet[2] = thisFrame.length % 256;
// add the frame to the packet:
for (int b = 0; b < thisFrame.length; b++) {
packet[b + 3] = thisFrame[b];
}
// checksum the command:
packet[packetLength - 1] = checkSum(thisFrame);
if (DEBUG) System.out.print("< ");
// send it out the serial port:
for (int c = 0; c < packet.length; c++) {
port.write(packet[c]);
if (DEBUG) System.out.print(parent.hex(packet[c], 2) + " ");
}
if (DEBUG) System.out.println();
}
public int[] getPacket() {
boolean gotAPacket = false; // whether the first byte was 0x7E
int packetLength = -1; // length of the dataArray
int[] thisdataArray = null; // the dataArray to return
int checksum = -1; // the checksum as received
int localChecksum = -1; // the chacksum as we calculate it
// read bytes until you get a 0x7E
port.clear(); // flush the buffer so that no old data comes in
while (port.available() < 1) {; // do nothing while we wait for the buffer to fill
}
// this is a good header. Get ready to read a packet
if (port.read() == 0x7E) {
gotAPacket = true;
}
// if the header byte is good, try the rest:
if (gotAPacket) {
// read two bytes
while (port.available() < 2) {; // wait until you get two bytes of length
}
int lengthMSB = port.read(); // high byte for length of packet
int lengthLSB = port.read(); // low byte for length of packet
// convert to length value
packetLength = (lengthLSB + (lengthMSB << 8));
// sanity check: if the packet is too long, bail.
if (packetLength > 200) {
System.out.println("Length (" + packetLength + ") too long, discarding packet.");
return null;
}
if (DEBUG) System.out.print("> [" + packetLength + "]: ");
// read bytes until you've reached the length
while (port.available() < packetLength) {; // do nothing while we wait for the buffer to fill
}
// make an array to hold the data frame:
thisdataArray = new int[packetLength];
// read all the bytes except the last one into the dataArray array:
for (int thisByte = 0; thisByte < packetLength; thisByte++) {
thisdataArray[thisByte] = port.read();
if (DEBUG) System.out.print(parent.hex(thisdataArray[thisByte], 2) + " ");
}
while (port.available() < 1) {; // do nothing while we wait for the buffer to fill
}
// get the checksum:
checksum = port.read();
// calculate the checksum of the received dataArray:
localChecksum = checkSum(thisdataArray);
// if they're not the same, we have bad data:
if (localChecksum != checksum) {
if (DEBUG) System.out.println();
System.out.print(
"Bad checksum, discarding packet. Local: " + parent.hex(localChecksum % 256));
System.out.println(", Remote: " + parent.hex(checksum) + ", Length: " + packetLength);
// if the checksums don't add up, clear the dataArray array:
thisdataArray = null;
}
}
// makes a nice printing for debugging:
if (DEBUG) System.out.println("!");
// return the data frame. If it's null, you got a bad packet.
return thisdataArray;
}
