MK715R 查看數據表（PDF） - Integrated Circuit Systems

零件编号

产品描述 (功能)

生产厂家

MK715R

Touch Screen Controller

Integrated Circuit Systems 

MK715

Measuring Touch Pressure

Measuring touch pressure can only be performed on 4-wire touchscreens. In normal operation, the screen drivers

force XH high and XL to ground and measure the voltage on the other plate. A schematic of this is as follows:

Voltage measured on YH is the same as at K

and L giving the X co-ordinate.

When RDPRESA is asserted, the screen drive changes as follows (XSEL=1):

Voltage measured on YH is now the voltage at

L. Voltage measured at XL is now the voltage

at K. The difference is proportional to the

touch pressure.

When RD1PT is asserted, the converter automatically performs two conversions. The status of the XSEL bit identifies

the conversions. The following table gives the four measurements available.

RDPRESB RDPRESA

0

1

0

1

1

0

1

0

XSEL

0

1

0

1

DRIVE

YH, XL

XH, YL

YH, XL

XH, YL

PIN MEASURED

XH

YH

YL

XL

Both points returned

in one conversion pair.

Both points returned

in one conversion pair.

From these four measurements, the resistance of the touch can be calculated as a proportion of x-plate and y-plate

resistance. See the next section for suggestions about calculating the touch resistance. From this, the touch pressure

can be inferred. See the table on page 7 for the correct register sequencing of the converter.

16

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