BU21028FV-M Datasheet, PDF (15/36 Pages) Rohm – 4-wire Resistive Touch Screen Controller

BU21028FV-M
Command Mode
In Command Mode, BU21028FV-M operates totally under the control of the host processor. In order to take touch data, the
host processor needs to control BU21028FV-M 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.
Sensing sequence (Command mode) flow chart
Start
White box: Control flow
Charcoal gray box: Divergence by the use function
Light gray box: For periodic calibration
INT pin = H
(No interrupt)
Yes
Interrupt
No
Count = 0
(For periodic calibration)
Stop timer
(For periodic calibration)
Timer interrupt
No
Yes
Stop timer
(For periodic calibration)
Periodic calibration
for 2-points detection circuit
Enable interrupt MASK on HOST
X
Send X-axis drivers status command
(CF = 0x8)
X coordinate convert and read
0xE0 (CF = 0xC) Burst-read 4 byte
（Use only single touch case : 2 byte）
(Need plural data case: repeat dashed X box)
Y
Send Y-axis drivers status command
(CF = 0x9)
Y coordinate convert and read
0xE8 (CF = 0xD) Burst-read 6 byte
（Use only single touch case : 2 byte）
(Need plural data case: repeat dashed Y box)
Start timer
(For periodic calibration)
Disable interrupt MASK on HOST
Z
Send Z-way drivers status command
(CF = 0xA)
Z coordinate convert and read
0xF0 (CF = 0xE) Burst-read 4 byte
（Use only single touch case : 2 byte）
(Need plural data case: repeat dashed Z box)
Use only single touch detection
Yes
single
coordinate data calculation
Use 2-points detection
No
2-points
coordinate data calculation
INT pin = H
(No interrupt)
No
Yes
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27.May.2016 Rev.002