BU21049GUL Datasheet, PDF (15/26 Pages) Rohm – 4-wire Resistive Touch Screen Controller

BU21049GUL
Datasheet
Auto mode
The BU21049GUL takes all of the detected touch pressure and the touch data by automatic control. An interrupt signal is
transmitted to the timing which the 1st data taken after detecting touch pressure completed.
In order for the BU21049GUL to continue taking touch data without control of the host processor, the host processor does
not need to control a touch screen.
Auto mode operation is started to the timing which received SCAN-XYZ (CF=0000) from the host processor. The INT pin is
not concerned with a touch state, but is set to “H” until the 1st touch data is acquired after a start of operation.
Table. Auto 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 turn on Z drivers(*1).
3
The BU21049GUL converts the Z data from the touch scren and saves a result to temporary.
4
After the BU21049GUL turn off Z drivers, it turns on X drivers and makes the X-axis of the touch screen
turn on electricity.
5
The BU21049GUL converts the X data from the touch scren and saves a result to temporary.
6
After the BU21049GUL turn off X drivers, it turns on Y drivers and makes the Y-axis of the touch screen
turn on electricity.
7
The BU21049GUL converts the Y data from the touch scren and saves a result to temporary.
8
The BU21049GUL checks touch pressure.
When touch pressure is detected, all conversion result copied to internal registers in the BU21049GUL,
transmit interrupt signal to the host processor and it turn back to step 2.
When touch pressure is undetected, all conversion result are cancelled, transmission of an interrupt signal
is stopped, and it turn back to step 1.
9
The host processor does the mask of the interruption after receiving an interrupt signal.
10
The host processor received all touch data and 2 points data(total 14 byte) via I2C bus and convert to
touch coordinates.(*2)
When not detecting 2 points, only touch data(8 byte) is received.
11
The host processor checks the touch pressure from the INT pin or status register in the BU21049GUL.
Trun back to step 10 when there is touch pressure.
(*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.
Touch screen scan flow 3(XYZ scan)
HOST
SCAN XYZ
(CF=0x0)
INT
BU21049
Detecting
touch
Z1 coordinate
tPON = 710us
tDLY1 = 1.5us
tADC = 18us
tDLY2 = 1.0us
tTIME_ST_ADC = register (addr.0x2)
tINTVL = register (addr.0x2)
tSMPL = register (addr.0x1)
tConv3
Sample and Conversion
Z2 coordinate X coordinate
Y coordinate
tConv3 = tPON + tDLY1 + (tTIME_ST_ADC + (tADC * tSMPL) + tDLY2) * 3
(*1) Time is calculated with the oscillating frequency of the internal OSC is 8MHz.
(*2) In the case of PDM=1, tPON(s) is set to zero except for the first time.
(*3) An order of taking each touch data, etc. cannot be changed.
Read
result of SCAN XYZ
tINTVL
Wait (INTVL_TIME)
Sample and Conversion
Z1 coordinate Z2.
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TSZ22111・15・001
15/23
TSZ02201-0Y1Y0F300010-1-2
31.JAN.2012 Rev.001