USB-read loosing packets

[tspecht]

Hey there,

don't know if this is a general issue or just mine. I'm trying to read at baud-rate 9600 from an Arduino UNO, but unfortunately it seems, that there are multiple possible outcomes to the result: 1/3 of the cases, nothing is transmitted, 1/3 everything works out quite well, the last 1/3 of the times, only parts of the data get transmitted. Any suggestions?

[DaveMelcher]

I've seen this as well. Also 9600. I've got the Arduino doing a Serial.print() once a second, sending a complete word each time. When I have the Android read once a second, I lose most of the characters, usually only getting one or two from each packet. When I have the Android read more often, I lose fewer characters. At 10 reads a second, it only drops one or two characters out of the 45 character sentence. That still seems like a lot of drops to me.

When I use the serial monitor in the Arduino IDE, the communication seems to go just fine. No drops, no delays.

[DaveMelcher]

Hey, FTDriver is using bulkTransfer() in the read(). According to the docs:
http://developer.android.com/guide/topics/connectivity/usb/host.html
bulkTransfer() is for synchronous communication. I'm calling read() from time to time. That sounds like asynchronous to me.

@scriptedSheep , how often are you calling read()? And does your success rate increase if you call read() more often?

[ksksue]

Have you used USB Serial Monitor Lite?
https://play.google.com/store/apps/details?id=jp.ksksue.app.terminal
Does the problem occur?
USB Serial Monitor Lite uses FTDriver.

[DaveMelcher]

USB Serial Monitor Lite seems to work just fine.
How often are you calling FTDriver.read()?

I got my app to work by adding a background thread that does nothing but try a bulkTransfer(), and if there's any data, it stores it for the next read(), then repeat as fast as possible. I think the more often you call bulkTransfer(), the fewer bytes you drop. I haven't figured out what the limit is for dropping none.

[ksksue]

USB Serial Monitor Lite's read function is running on one thread.
If you use it on a multithread, you might try to use synchronized function.

synchronized(mFTDriver) {
mFTDriver.read(moemoe);
}

[DaveMelcher]

How often are you calling FTDriver.read()?

I've run some experiments, and if I do the bulkTransfer at about 20Hz or faster, I seem to get all of my test data. But if I try to make runOnUiThread() call that fast, it bogs down.

[ksksue]

You can see here how often I calling it.
https://github.com/ksksue/Android-USB-Serial-Monitor-Lite/blob/master/AndroidUSBSerialMonitorLite/src/jp/ksksue/app/terminal/AndroidUSBSerialMonitorLite.java#L444
I write Thread.sleep(20) so it's about 10-40Hz.

[pablichjenkov]

@ksksue @scriptedSheep @zacnelson @DaveMelcher .Hi guys I was trying the library without the Thread.sleep(50) and it seems to miss some data packet after a random number of callings to the read method. Has anyone experienced this issue. I am guessing is a problem with android internal API