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Touchscreen Responsiveness in Matrix vs ts_test

Brad Griffis
Guru*** 125430 points

AM335x EVM
SDK 7.00

If I boot the stock SDK 7.00 image and move my finger all around the screen of the Matrix GUI the mouse seems to track very accurately and quickly.

However, if I exit the Matrix GUI and launch ts_test to do some simple drawing, I see major lag and discontinuities.

It seems like both Matrix GUI and ts_test are both sitting on top of tslib.  Can anyone explain why ts_test is so much worse?

  • 0
    TI__Mastermind 25235 points

    Hi Brad,

    There is an issue with the touch screen in SDK v7. The factory team is aware of it and working on it, but as far as I know they don't have a schedule yet for an estimated fix.

    Best regards,
    Miroslav

  • 0 in reply to Miroslav Kiradzhiyski XID
    TI__Guru*** 125430 points

    You're right...  I went and retested with SDK 6.00 and ts_test seems to work fine (speed wise) in that environment.  There's a separate issue I'm debugging, though I will likely start a separate thread once I've better characterized the problem.

  • 0 in reply to Brad Griffis
    TI__Guru*** 125430 points

    I have been working on this issue and I have some explanations of our observations:

    1. The ts_test performance is much worse than the Matrix GUI itself because ts_test is printing out all the coordinates to the UART.  Because the UART is "slow" this causes delays in the ts_test application's ability to read the pixels and update the screen.  While ts_test is waiting for the printf to complete it is missing movement.  Simply invoking it as "/usr/bin/ts_test > /dev/null" will pipe the output to /dev/null and avoid these delays.
    2. The ts_test performance is better in SDK 6.00 than SDK 7.00 because there was some rudimentary filtering being done inside the ISR in SDK 6.00.  This reduced the amount of prints which reduced the number of missed samples.  Both SDK 6.00 and SDK 7.00 perform (much) better when piping the output to /dev/null.