CODEWITHSUNDEEP
linuxtouchlinux-device-driver
pRAShANT
pRAShANT

Reputation: 523

Calculate latency for touch screen UI running on ARM controller board running Linux

I have an embedded board which has ARM controller, runs Linux as OS, which also has touch based screen. The data to the screen is taken from the Frame Buffer (/dev/fb0). Is there any way we can calculate the response time between two UI screen switching occurs when any option is selected by touch?

Upvotes: 1

Views: 405

Answers (1)

TheCodeArtist
TheCodeArtist

Reputation: 22487

There are 3 latencies involved in the above scenario

1. Time taken for the touchscreen to register the finger and raise an input-event.

  • Usually a few milliseconds.
  • Enable FTRACE and log the following with timestamps
    -- ISR
    -- Entry of Bottom-half
    -- Invoking of input_report()

2. Time taken by the app responsible for the GUI to update it.

  • Depending upon the app/framework, usually the most significant contributor to latency.
  • Add normal console logs with timestamps in the GUI app's code
    -- upon receiving the input event
    -- just before the command to modify the GUI

3. The time taken by the display to update.

  • Usually within 15-30 milliseconds

The final latency is a sum-total of the above 3 latencies.

Upvotes: 2

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