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FTDI driver: Filter status bytes

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Filter status bytes at the beginning of every USB package received from
FTDI serial adapters
This commit is contained in:
Felix Hädicke 2013-05-17 18:36:57 +02:00 committed by mike wakerly
parent b709823906
commit eca40d6b11
1 changed files with 31 additions and 9 deletions
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38
UsbSerialLibrary/src/com/hoho/android/usbserial/driver/FtdiSerialDriver.java
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@ -166,6 +166,32 @@ public class FtdiSerialDriver extends CommonUsbSerialDriver {
*/ */
private static final boolean ENABLE_ASYNC_READS = false; private static final boolean ENABLE_ASYNC_READS = false;
/**
* Filter FTDI status bytes from buffer
* @param src The source buffer (which contains status bytes)
* @param dest The destination buffer to write the status bytes into (can be src)
* @param totalBytesRead Number of bytes read to src
* @param maxPacketSize The USB endpoint max packet size
* @return The number of payload bytes
*/
private final int filterStatusBytes(byte[] src, byte[] dest, int totalBytesRead, int maxPacketSize) {
final int packetsCount = totalBytesRead / maxPacketSize + 1;
for (int packetIdx = 0; packetIdx < packetsCount; ++packetIdx) {
final int count = (packetIdx == (packetsCount - 1))
? (totalBytesRead % maxPacketSize) - MODEM_STATUS_HEADER_LENGTH
: maxPacketSize - MODEM_STATUS_HEADER_LENGTH;
if (count > 0) {
System.arraycopy(src,
packetIdx * maxPacketSize + MODEM_STATUS_HEADER_LENGTH,
dest,
packetIdx * (maxPacketSize - MODEM_STATUS_HEADER_LENGTH),
count);
}
}
return totalBytesRead - (packetsCount * 2);
}
/** /**
* Constructor. * Constructor.
* *
@ -253,17 +279,13 @@ public class FtdiSerialDriver extends CommonUsbSerialDriver {
final int readAmt = Math.min(dest.length, mReadBuffer.length); final int readAmt = Math.min(dest.length, mReadBuffer.length);
totalBytesRead = mConnection.bulkTransfer(endpoint, mReadBuffer, totalBytesRead = mConnection.bulkTransfer(endpoint, mReadBuffer,
readAmt, timeoutMillis); readAmt, timeoutMillis);
}
if (totalBytesRead < MODEM_STATUS_HEADER_LENGTH) { if (totalBytesRead < MODEM_STATUS_HEADER_LENGTH) {
throw new IOException("Expected at least " + MODEM_STATUS_HEADER_LENGTH + " bytes"); throw new IOException("Expected at least " + MODEM_STATUS_HEADER_LENGTH + " bytes");
} }
final int payloadBytesRead = totalBytesRead - MODEM_STATUS_HEADER_LENGTH; return filterStatusBytes(mReadBuffer, dest, totalBytesRead, endpoint.getMaxPacketSize());
if (payloadBytesRead > 0) {
System.arraycopy(mReadBuffer, MODEM_STATUS_HEADER_LENGTH, dest, 0, payloadBytesRead);
} }
return payloadBytesRead;
} }
} }