The response time is defined as the time between the finger touch event on the touch screen and the interrupt signal generated by the touch screen controller. The measurement method is to electronically touch the environment of a simulated finger touch screen, or move a simulated finger on the panel. The response time is particularly important because it directly affects the speed of the user's moving fingers on the screen, panning or flicking operations, and writing on the screen with a finger or pen. A touch screen with a slow response time will have a short pause and no movement can be detected. The response time of the touch screen is part of the system response time, which includes:
1) X, y axis scan. The time it takes for the touch screen controller to scan and measure changes in capacitance on the sensor.
2) Finger detection. Compare the change of the panel capacitance with the pre-defined default value of the finger. If the change range exceeds the default value of the finger, the finger touch will be detected.
3) Finger position. Calculate based on the result data obtained by multiple sensors to determine the actual position of the finger.
4) Finger tracking. When there are multiple fingers on the sensor, each finger must be correctly identified and assigned a unique identification symbol.
5) Interrupt delay. Refers to the delay between indication and service on the host. In most systems, this delay does not exceed 10 (Vs).
6) Communication. Generally, the system uses I2C at 400kHz, or SPI at 1MHz to communicate with the host.
There are many technologies on the market that can be used to shorten the response time. The key lies in the intelligence of the touch screen chip. The more creative method only needs to scan part of the screen to detect the position of the finger. When the finger is detected, it can quickly scan and calculate The actual positioning of the finger saves power and time. Another technique is parallel processing, which uses different hardware components for scanning, finger processing, and communication, so that these tasks are performed simultaneously. Using highly optimized algorithms for finger detection, finger positioning and finger identification (ID) can shorten processing and response time.
