STMPE811_09 datasheet(45/64 Pages) STMICROELECTRONICS

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STMPE811

Touch screen controller programming sequence

Doc ID 14489 Rev 2

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Touch screen controller programming sequence

The following are the steps to configure the touch screen controller (TSC):

Disable the clock gating for the touch screen controller and ADC in the

SYS_CFG2 register.

Configure the touch screen operating mode and the window tracking index.

A touch detection status may also be enabled through enabling the corresponding

interrupt flag. With this interrupt, the user is informed through an interrupt when

the touch is detected as well as lifted.

Configure the TSC_CFG register to specify the “panel voltage settling time”, touch

detection delays and the averaging method used.

A windowing feature may also be enabled through TSCWdwTRX, TSCWdwTRY,

TSCWdwBLX and TSCWdwBLY registers. By default, the windowing covers the

entire touch panel.

Configure the TSC_FIFO_TH register to specify the threshold value to cause an

interrupt. The corresponding interrupt bit in the interrupt module must also be

enabled. This interrupt bit should be masked off during data fetching from the

FIFO in order to prevent an unnecessary trigger of this interrupt. Upon completion

of the data fetching, this bit can be re-enabled

By default, the FIFO_RESET bit in the TSC_FIFO_CTRL_STA register holds the

FIFO in Reset mode. Upon enabling the touch screen controller (through the EN

bit in TSC_CTRL), this FIFO reset is automatically deasserted. The FIFO status

may be observed from the TSC_FIFO_CTRL_STA register or alternatively through

the interrupt.

Once the data is filled beyond the FIFO threshold value, an interrupt is triggered

(assuming the corresponding interrupt is being enabled). The user is required to

continuously read out the data set until the current FIFO size is below the

threshold, then, the user may clear the interrupt flag. As long as the current FIFO

size exceeds the threshold value, an interrupt from the touch screen controller is

sent to the interrupt module. Therefore, even if the interrupt flag is cleared, the

interrupt flag will automatically be asserted, as long as the FIFO size exceeds the

threshold value.

The current FIFO size can be obtained from the TSC_FIFO_Sz register. This

information may assists the user in how many data sets are to be read out from

the FIFO, if the user intends to read all in one shot. The user may also read a data

set by a data set.

The TSC_DATA_X register holds the X-coordinates. This register can be used in

all touch screen operating modes.

The TSC_DATA_Y register holds the Y-coordinates. TSC_DATA_Y register holds

the Y-coordinates.

The TSC_DATA_Z register holds the Z value. TSC_DATA_Z register holds the Z-

coordinates.

The TSCDATA_XYZ register holds the X, Y and Z values. These values are

packed into 4 bytes. This register can only be used when the touch screen

operating mode is 000 and 001. This register is to facilitate less byte read.

For the TSC_FRACT_Z register, the user may configure it based on the touch

screen panel resistance. This allows the user to specify the resolution of the Z

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