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usb-serial-for-android: Implement timeout-handling

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Since the Android USB stack and subsequently the usb-serial-for-android
driver have problems with read-timeouts, the read-timeout is now
implemented in AndroidSerial.java. Also, DC_STATUS_TIMEOUT is returned
if there are less bytes returned than expected.

Different chipsets seem to behave differently with
usb-serial-for-android. On CP210x the read blocks until there is some
data here, but on FTDI the chip seems to return whatever is currently in
the buffer (so 0 bytes if the buffer is empty). This different behaviour
should be mitigated by the changes by this commit.

Signed-off-by: Christof Arnosti <charno@charno.ch>
This commit is contained in:
Christof Arnosti 2020-03-08 15:25:55 +01:00 committed by Dirk Hohndel
parent fe932059fe
commit b15b9c6cd0
2 changed files with 13 additions and 5 deletions
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12
android-mobile/src/org/subsurfacedivelog/mobile/AndroidSerial.java
View file

@ -19,6 +19,7 @@ import java.util.Queue;
import java.util.List;
import java.util.LinkedList;
import java.lang.Math;
import java.util.Date;
public class AndroidSerial {
@ -221,17 +222,20 @@ public class AndroidSerial {
Log.d(TAG, "read length: " + data.length);
int toReadFromHwLength = data.length - readBuffer.size();
int arraylength = (toReadFromHwLength % 64) != 0 ? toReadFromHwLength + (64 - (toReadFromHwLength % 64)): toReadFromHwLength; // use blocks of 64 for reading
// When we don't have enough in the buffer, try to read from HW
if (toReadFromHwLength > 0) {
long startTime = (new Date()).getTime();
// while we don't have enough in the buffer, try to read from HW until there is enough or timeout is reached.
while (toReadFromHwLength > 0 && (startTime + timeout > (new Date()).getTime() || timeout == 0)) {
// Read and append to buffer
byte[] readFromHwData = new byte[arraylength];
int actuallyReadFromHwLength = usbSerialPort.read(readFromHwData, 0); // With this it works... But the timeout is ignored! Fix this!
int actuallyReadFromHwLength = usbSerialPort.read(readFromHwData, 0); // This behaves differently on different chipsets. CP210x blocks, FTDI seems to return instantly.
for (int i = 0; i < actuallyReadFromHwLength; i++ ) {
readBuffer.add(readFromHwData[i]);
}
toReadFromHwLength = data.length - readBuffer.size();
arraylength = (toReadFromHwLength % 64) != 0 ? toReadFromHwLength + (64 - (toReadFromHwLength % 64)): toReadFromHwLength; // use blocks of 64 for reading
}
//Log.d(TAG, "read buffer: " + printQueue(readBuffer));

6
core/serial_usb_android.cpp
View file

@ -141,7 +141,11 @@ static dc_status_t serial_usb_android_read(void *io, void *data, size_t size, si
env->GetByteArrayRegion(array, 0, retval, (jbyte *) data);
env->DeleteLocalRef(array);
TRACE (device->context, "%s: actual read size: %i", __FUNCTION__, retval);
return DC_STATUS_SUCCESS;
if (retval < size)
return DC_STATUS_TIMEOUT;
else
return DC_STATUS_SUCCESS;
}