BU21049GUL Datasheet, PDF (13/26 Pages) Rohm – 4-wire Resistive Touch Screen Controller

BU21049GUL
Datasheet
Command mode
The BU21049GUL operates according to the control (command) by the host processor completely.
In order to take touch data, as long as touch pressure is ON, the host processor needs to continue controlling the
BU21049GUL. Moreover, since it is necessary to certainly transmit a command for taking touch data, processing of a host
interface becomes active compared with an auto system between ON of touch pressure.
Table. Command method sequence
step touch screen operation
1 not touched The BU21049GUL is in idle state(power down).
The host processor operates the other process or keep the idle state.
2
touched The BU21049GUL detect a touch and transmit interrupt to the host processor.
3
The host processor disable interrupt from the BU21049GUL.
4
The host processor transmit command of X data conversion via I2C bus.
5
The BU21049GUL turns on X drivers and makes the X-axis of the touch screen turn on electricity.
6
The BU21049GUL converts the X data from the touch screen ad transmits via I2C bus.
7
The host processor receives center data and 2 points data(total 4 byte).
When not detecting 2 points, only center data(2 byte) is received.
When the host processor need 2 or more data by filter processing etc., it repeats step 4~7.
8
The host processor transmit command of Y data conversion via I2C bus.
9
After the BU21049GUL turns off X drivers, it turns on Y drivers and makes the Y-axis of the touch screen turn
on electricity.
10
The BU21049GUL converts the Y data from the touch screen ad transmits via I2C bus.
11
The host processor receives center data and 2 points data and ghost data(total 6 byte).
When not detecting 2 points, only center data(2 byte) is received.
When the host processor need 2 or more data by filter processing etc., it repeats step 8~11.
12
The host processor transmit command of Z data conversion via I2C bus.
13
After the BU21049GUL turns off Y drivers, it turns on Z drivers(*1) and makes the Z-axis of the touch screen
turn on electricity.
14
The BU21049GUL converts the Z data from the touch screen ad transmits via I2C bus.
15
The host processor receives Z data(total 4 byte).
When the host processor need 2 or more data by filter processing etc., it repeats step 12~15.
16
The host processor calculates all the data and covert into touch coordinates.
17
The host processor checks the touch pressure from the INT pin or status register in the BU21049GUL. Step
4～16 repeated when there is touch pressure.
18 not touched turn back to step 1.
(*1) Z driver: YP=VDD, XN=GND state
(*2) Refer to the dual coordinates conversion (p. 17) for the conversion on coordinates from read data.
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TSZ22111・15・001
13/23
TSZ02201-0Y1Y0F300010-1-2
31.JAN.2012 Rev.001