stmpe610 STMicroelectronics, stmpe610 Datasheet - Page 29

• Manufacturer Part Number: stmpe610
• Description: Advanced Touch Screen Controller With 6-bit Port Expander
• Manufacturer: STMicroelectronics

STMPE610
10
10.1
Touch screen controller
The STMPE610 is integrated with a hard-wired touch screen controller for 4-wire resistive
type touch screen. The touch screen controller is able to operate completely autonomously,
and will interrupt the connected CPU only when a pre-defined event occurs.
Figure 9.
Driver and switch control unit
The driver and switch control unit allows coordination of the ADC and the MUX/switch. With
the coordination of this unit, a stream of data is produced at a selected frequency.
The touch screen drivers can be configured with 2 current ratings: 20 mA or 50 mA. In the
case where multiple touch-down on the screen is causing a short, the current from the driver
is limited to these values. Tolerance of these current setting is +/- 25%.
Movement tracking
The "Tracking Index" in the TSC_CTRL register specifies a value, which determines the
distance between the current touch position and the previous touch position. If the distance
is shorter than the tracking index, it is discarded.
The tracking is calculated by summation of the horizontal and vertical movement. Movement
is only reported if:
(Current X - Previously Reported X) + (Current Y - Previously Reported Y) > Tracking Index
If pressure reporting is enabled (X/Y/Z), an increase in pressure will override the movement
tracking and report the new data set, even if X/Y is within the previous tracking index. This is
to ensure that a slow touch will not be discarded.
If pressure data is not used, select X/Y mode in touch screen data acquisition. (Opmode
field in TSCControl register).
FIFO
Touch screen controller block diagram
interrupt control
window tracking
Movement
FIFO
&
&
switch control
10/12 bit
Driver
ADC
&
Touch screen controller
drivers
Switch
&
s
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