BU21029MUV Datasheet, PDF (15/29 Pages) Rohm – 4-wire Resistive Touch Screen Controller

BU21029MUV
Datasheet
Auto Mode
In Auto Mode, BU21029MUV automatically takes all detected touch and pressure data. An interrupt signal for the 1st data
taken is transmitted after detection of touch pressure has been completed. Since BU21029MUV automatically takes data
whenever touch pressure is detected, the host processor does not need to control the touch screen.
When operating in this mode, there is a possibility for touch detection to stop due to touch screen chattering noise, power
supply noise, etc. Thus, the host processor should periodically refresh BU21029MUV by transmitting the command
CF=0000.
Auto Mode of operation starts when SCAN-XYZ (CF=0000) is received from the host processor. The INT pin is not
concerned with any touch state. It is set to “H” until the 1st touch data from the start of operation is acquired.
Table 8. Auto Method Sequence
step touch screen operation
1
not touched The BU21029MUV is in idle state(power down).
The host processor operates the other process or keeps the idle state.
2
touched The BU21029MUV detects touch and turns on Z drivers(*1).
3
The BU21029MUV converts the Z data from the touch screen and saves the result temporarily.
4
After the BU21029MUV turns off the Z drivers, it turns on the X drivers and makes the X-axis of the
touch screen turn on power.
5
The BU21029MUV converts the X data from the touch scren and saves the result temporarily.
6
After the BU21029MUV turns off the X drivers, it turns on the Y drivers and makes the Y-axis of the
touch screen turn on power.
7
The BU21029MUV converts the Y data from the touch scren and saves the result temporarily.
8
The BU21029MUV checks touch pressure.
When touch pressure is detected, all conversion results are copied to the internal registers of the
BU21029MUV and interrupt signal is transmitted to the host processor. Then the process returns to
step 2.
When no touch pressure is detected, all conversion result are cancelled and transmission of an
interrupt signal is stopped. Then the process returns to step 1.
9
The host processor does the mask of the interruption after receiving an interrupt signal.
10
The host processor receives all touch and 2-point data (total of 14 bytes) via I2C bus and converts to
them to touch coordinates.(*2)
When not detecting 2 points, only touch data (8 bytes) is received.
11
The host processor checks the touch pressure from the INT pin or status register of BU21029MUV. It
returns to step 10 when there is touch pressure and to step 1 when there is none.
(*1) Z driver: YP=VDD, XN=GND state
(*2) Refer to the dual coordinate’s conversion (p. 17) for the conversion of coordinates from read data.
(*3) The host processor can refresh at any timing, and recommended timing is in sequence with step 1.
HOST
INT
SCAN XYZ
(CF=0x0)
BU21029
Detecting
touch
Read
result of SCAN XYZ
tConv4
Z1 coordinate
Sample and Conversion
Z2 coordinate
X coordinate
Y coordinate
tINTVL
Wait (INTVL_TIME)
Sample and Conversion
Z1 coordinate Z2.
Figure 8. Touch screen scan flow 3 (XYZ scan)
tPON
= 710us
tDLY1
= 1.5us
tADC
= 18us
tDLY2
= 1.0us
tTIME_ST_ADC = register (addr.0x2)
tINTVL
= register (addr.0x2)
tSMPL
= register (addr.0x1)
tConv4
= tPON + tDLY1 + (tTIME_ST_ADC + (tADC * tSMPL) * 2 + tDLY2) * 3
(*1) Time is calculated with the oscillating frequency of the internal OSC is 8MHz.
(*2) In the case of PDM=1, every tPON(s) is zero except for the first one.
(*3) The order of taking each touch data, etc. cannot be changed.
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TSZ22111・15・001
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TSZ02201-0Y1Y0F300110-1-2
11.Nov.2013 Rev.004