BU21029GUL Datasheet, PDF (12/29 Pages) Rohm – 4-wire Resistive Touch Screen Controller

BU21029GUL
Datasheet
●Control Flow Chart
BU21029GUL has two operation modes, the command mode, wherein the device operates under the control of the host
processor, and auto mode, wherein the device operates by automatic control.
In order to use two-point detection, it is necessary to calibrate the circuit for this function by setting the correct state of
registers for panel perimeters (register Addr.0x3, 0x4). Calibration is performed by transmitting the command CF=0101
from the host processor. Take note that each register should be initialized after power on. Moreover, for two-point detection,
the interrupt signal from the IC should be enabled after performing parameter calibration.
Table 6. The BU21029GUL Power-on Sequence
step
state
operation
1
Power-on
Power supply is turned on and reset is issued
Disable (mask) interruption of the BU21029GUL is set.
2
initialization 1 After the waiting time from the issuance of reset, each register of BU21029GUL is initialized by the
（For 2 points host processor via the I2C bus.
detecition only）
3
initialization 2 The host processor checks if the screen is touched though the INT pin or the status register of
（For 2 points BU21029GUL. This step is repeated until touch is detected.
4
detecition only） The host processor transmits the calibration command (CF=0101) via the I2C bus.
5
BU21029GUL executes calibration of the two-point detection parameters and sets CALIB_DONE
status register to 1.
6
The host stays in stand by state until a fixed period of time or until the CALIB_DONE bit is turned on.
7
initialization　3 For auto mode control, the host processor transmit the SCAN-XYZ command via the i2C bus. For
(For Auto mode only) command control mode, this step is skipped.
8
Normal
If the host processor receives an interrupt signal from BU21029GUL, it executes the other process.
(finish)
If not, it stays idle until an interrupt signal is detected.
HOST CALIB
(CF=0x5)
Read
Status
INT
BU21029
Detecting
touch
tConv1
tConv1
tCalib
tConv1
tConv1
tCalib
Sample and Conversion Sample and Conversion Calibrate Sample and Conversion Sample and Conversion Calibrate Detecting
for X coordinate
for Y coordinate
parameters
for X coordinate
for Y coordinate
parameters
touch
Figure 5. Calibration Flow
tPON
= 710us
tDLY1
= 1.5us
tADC
= 18us
tDLY2
= 1.0us
tTIME_ST_ADC = register (addr.0x2)
tSMPL
= register (addr.0x1)
tConv1
tCalib
= tPON + tDLY1 + (tTIME_ST_ADC + (tADC * tSMPL) * 2 + tDLY2)
= 1 internal clock
(*1) Even if the part with dashed lines is not performed, read status does not influence the operation.
(*2) Except the first one, tPON(s) is always zero.
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TSZ22111・15・001
12/26
TSZ02201-0Y1Y0F300120-1-2
11.Nov.2013 Rev.002