BU21029GUL Datasheet, PDF (13/29 Pages) Rohm – 4-wire Resistive Touch Screen Controller

BU21029GUL
Datasheet
●Command Mode
In Command Mode, BU21029GUL operates totally under the control of the host processor. In order to take touch data, the
host processor needs to control BU21029GUL when there is touch pressure. Since it is necessary for the host processor to
issue a command in order to get data, the processing of a host interface in between the presence of touch pressure
becomes more active compared with the auto system.
Table 7. Command Method Sequence
touch screen operation
not touched The BU21029GUL is in idle state(power down).
The host processor operates the other process or stays in the idle state.
touched The BU21029GUL detects a touch and transmits interrupt signal to the host processor.
The host processor detects a disabled interrupt signal from the BU21029GUL.
The host processor transmits the command for X data conversion via I2C bus.
The BU21029GUL turns on the X drivers and makes the X-axis of the touch screen turn on the power.
The BU21029GUL converts the X data from the touch screen and transmits via I2C bus.
The host processor receives the center data and the 2-point data (total of 4 bytes).
If there is no 2-point detection, only the center data (2 bytes) is received.
if the host processor needs 2 or more data by filter processing etc., it repeats steps 4~7.
The host processor transmit command of Y data conversion via I2C bus.
After the BU21029GUL turns off the X drivers, it turns on the Y drivers and makes the Y-axis of the touch
screen turn on the power.
The BU21029GUL converts the Y data from the touch screen ad transmits via I2C bus.
The host processor receives the center data, the 2-point data, and ghost data (total of 6 bytes).
If there is no 2-point detection, only the center data (2 bytes) is received.
if the host processor needs 2 or more data by filter processing etc., it repeats steps 8~11.
The host processor transmits the command for Z data conversion via I2C bus.
After the BU21029GUL turns off the Y drivers, it turns on the Z drivers(*1) and makes the Z-axis of the touch
screen turn on the electricity.
The BU21029GUL converts the Z data from the touch screen ad transmits via I2C bus.
The host processor receives the Z data (total of 4 bytes).
if the host processor needs 2 or more data by filter processing etc., it repeats steps 12~15.
The host processor calculates all the data and coverts them into touch coordinates.
The host processor checks the touch pressure from the INT pin or the status register of the BU21029GUL.
Steps 4～16 are repeated when there is touch pressure.
not touched Return to step 1.
(*1) Z driver: YP=VDD, XN=GND state
(*2) Refer to the dual coordinate conversion in p. 17 for the conversion of coordinates from read data.
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TSZ22111・15・001
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TSZ02201-0Y1Y0F300120-1-2
11.Nov.2013 Rev.002