com.bitalino.comm.BITalinoFrameDecoder Maven / Gradle / Ivy
/**
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy of
* the License at
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*/
/**
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy of
* the License at
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*/
package com.bitalino.comm;
import java.io.IOException;
/**
* {@link BITalinoFrame} decoder.
*/
final class BITalinoFrameDecoder {
/**
* Decode {@link com.bitalino.comm.BITalinoFrame}.
*
* @param buffer an array of byte.
* @return decoded {@link com.bitalino.comm.BITalinoFrame}
* @param analogChannels an array of int.
* @param totalBytes a int.
* @throws java.io.IOException if any.
* @throws com.bitalino.comm.BITalinoException if any.
*/
public static BITalinoFrame decode(final byte[] buffer,
final int[] analogChannels, final int totalBytes) throws IOException,
BITalinoException {
try {
BITalinoFrame frame = new BITalinoFrame();
final int j = (totalBytes - 1);
int x0 = 0, x1 = 0, x2 = 0, x3 = 0, out = 0, inp = 0;
final int CRC = (buffer[j - 0] & 0x0F) & 0xFF;
// check CRC
for (int bytes = 0; bytes < totalBytes; bytes++) {
for (int bit = 7; bit > -1; bit--) {
inp = (buffer[bytes]) >> bit & 0x01;
if (bytes == (totalBytes - 1) && bit < 4)
inp = 0;
out = x3;
x3 = x2;
x2 = x1;
x1 = out ^ x0;
x0 = inp ^ out;
}
}
// if the message was correctly received, start decoding
if (CRC == ((x3 << 3) | (x2 << 2) | (x1 << 1) | x0)) {
frame = new BITalinoFrame();
frame.setSequence(((buffer[j - 0] & 0xF0) >> 4) & 0xf);
frame.setDigital(0, (buffer[j - 1] >> 7) & 0x01);
frame.setDigital(1, (buffer[j - 1] >> 6) & 0x01);
frame.setDigital(2, (buffer[j - 1] >> 5) & 0x01);
frame.setDigital(3, (buffer[j - 1] >> 4) & 0x01);
// parse buffer frame
if (analogChannels.length >= 1)
frame.setAnalog(
analogChannels[0],
(((buffer[j - 1] & 0xF) << 6) | ((buffer[j - 2] & 0XFC) >> 2)) & 0x3ff);
if (analogChannels.length >= 2)
frame.setAnalog(
analogChannels[1],
(((buffer[j - 2] & 0x3) << 8) | (buffer[j - 3]) & 0xff) & 0x3ff);
if (analogChannels.length >= 3)
frame.setAnalog(
analogChannels[2],
(((buffer[j - 4] & 0xff) << 2) | (((buffer[j - 5] & 0xc0) >> 6))) & 0x3ff);
if (analogChannels.length >= 4)
frame.setAnalog(
analogChannels[3],
(((buffer[j - 5] & 0x3F) << 4) | ((buffer[j - 6] & 0xf0) >> 4)) & 0x3ff);
if (analogChannels.length >= 5)
frame.setAnalog(
analogChannels[4],
(((buffer[j - 6] & 0x0F) << 2) | ((buffer[j - 7] & 0xc0) >> 6)) & 0x3f);
if (analogChannels.length >= 6)
frame.setAnalog(analogChannels[5], (buffer[j - 7] & 0x3F));
} else {
frame = new BITalinoFrame();
frame.setSequence(-1);
}
return frame;
} catch (Exception e) {
throw new BITalinoException(BITalinoErrorTypes.DECODE_INVALID_DATA);
}
}
}