BU21029GUL Datasheet, PDF (6/29 Pages) Rohm – 4-wire Resistive Touch Screen Controller

BU21029GUL
Datasheet
●Host Interface Specification
The BU21029GUL controller operates as an I2C slave device. At the start of the communication, it receives an address
byte transmitted by the host processor and then then sends back an acknowledgement byte. The host processor can
transmit a command to execute conversion or to access registers only after receiving the acknowledgement for the
address byte. Communication ends when BU21029GUL receives a stop command.
●Address byte
On the address byte, the slave address for 2-wire interface is written on the upper 7 bits and the READ/WRITE bit is
written on the last bit. The upper six bits of the slave address are fixed to “100000” while the last bit is determined by the
“AD0” input.
Table 1. Serial Interface Slave Address Byte
MSB
LSB
D7
D6
D5
D4
D3
D2
D1
D0
1
0
0
0
0
0
A0
R/W
Bit D1: A0
Slave address bit0 (AD0)
Bit D0: R/W
1=read (reading data)
0=write (writing data)
●Command byte
The operation of BU21029GUL is dictated by the command byte. The host processor sets CID (D7) to 1 for conversion
function or to 0 for register access.
Table 2. Serial Interface Command Byte 1(CID=1)
MSB
D7
D6
D5
D4
D3
D2
1
CF
CMSK
Bit D7: Command Byte ID
1= Command Byte 1(starts the conversion function determined by CF (Bit D6-D3)
D1
PDM
LSB
D0
STP
Bits D6-D4: CF
Conversion function is selected as detailed below.
Table 3. BU21029GUL Conversion Function List
CF Description
0x0 Touch screen scan function: X, Y, Z1 and Z2 coordinates are converted.
0x1 NOP
0x2 Auxiliary input is converted.
0x3 Clipping value is changed.
0x4 Free scan function: Status of Driver and input of A/D is assigned by the Host.
0x5 Calibration: Parameters for dual touch detection are calibrated.
0x6 NOP
0x7 NOP
0x8 X+, X- driver status
0x9 Y+, Y- driver status
0xA Y+, X- driver status
0xB NOP
0xC Touch screen scan function: X coordinate is converted.
0xD Touch screen scan function: Y coordinate isconverted.
0xE Touch screen scan function: Z1 and Z2 coordinates are converted.
0xF Reserved
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11.Nov.2013 Rev.002