BU21028FV-M Datasheet, PDF (20/36 Pages) Rohm – 4-wire Resistive Touch Screen Controller

BU21028FV-M
Coordinates Data Calculation
The touch position for dual touch is converted to coordinates by the host processor by processing the data which the
BU21028FV-M outputs. The data outputted changes with the commands received from the host processor as shown in
Table1. The host processor should take data from the BU21028FV-M by burst read via I2C. When reception stops and
resumes before all data is taken, data is again outputted from Byte0.
When using only single point detection, it may be the end of reception once each coordinate is taken.
Table 9. The Output Data List of Each Command
0
X
Y
Z1
1 coordinate
coordinate
coordinate
2
X 2 points
Y 2 points
Z2
3
paramter
paramter
coordinate
4
5
Dummy
Ghost
parameter
Dummy
6
-
-
-
7
-
-
-
8
-
-
-
9
-
-
-
10
-
-
-
11
-
-
-
12
-
-
-
13
-
-
-
14
-
-
-
15
-
-
-
X coordinate
Y coordinate
Z1 coordinate
Z2 coordinate
X 2 points
paramter
Y 2 points
paramter
Ghost
parameter
Dummy
Table 10. The Output Data Format List
DATA
ByteH
ByteL
Bit07 Bit06 Bit05 Bit04 Bit03 Bit02 Bit01 Bit00 Bit07 Bit06 Bit05 Bit04 Bit03 Bit02 Bit01 Bit00
X coordinate X[11] X[10] X[9] X[8] X[7] X[6] X[5] X[4] X[3] X[2] X[1] X[0] 0
0
0
0
Y coordinate Y[11] Y[10] Y[9] Y[8] Y[7] Y[6] Y[5] Y[4] Y[3] Y[2] Y[1] Y[0] 0
0
0
0
Z1 coordinate Z1[11] Z1[10] Z1[9] Z1[8] Z1[7] Z1[6] Z1[5] Z1[4] Z1[3] Z1[2] Z1[1] Z1[0] 0
0
0
0
Z2 coordinate Z2[11] Z2[10] Z2[9] Z2[8] Z2[7] Z2[6] Z2[5] Z2[4] Z2[3] Z2[2] Z2[1] Z2[0] 0
0
0
0
X 2 points
parameter
PX[9] PX[8] PX[7] PX[6] PX[5] PX[4] PX[3] PX[2] PX[1] PX[0]
0
0
0
0
0 SPX
Y 2 points
parameter
PY[9] PY[8] PY[7] PY[6] PY[5] PY[4] PY[3] PY[2] PY[1] PY[0]
0
0
0
0
0 SPY
Ghost
GH[11] GH[10] GH[9] GH[8] GH[7] GH[6] GH[5] GH[4] GH[3] GH[2] GH[1] GH[0] 0
0
0 SGH
parameter
(*1)The ByteH is the even number Byte. The ByteL is the odd number Byte. It means that X coordinates are ByteH=Byte0 and ByteL=Byte1 when it is taken
with a command method.
X coordinate: Touched coordinate of X. It becomes gravity center coordinate of 2 points at dual touch.
X = ByteH * 16 + ByteL / 16
Y coordinate: Touched coordinate of Y. It becomes gravity center coordinate of 2 points at dual touch.
Y = ByteH * 16 + ByteL / 16
Z1 coordinate: Touched coordinate of Z1. It’s used in calculating touch pressure.
Z1 = ByteH * 16 + ByteL / 16
Z2 coordinate: Touched coordinate of Z2. It’s used in calculating touch pressure.
Z2 = ByteH * 16 + ByteL / 16
X 2-point touch parameter: It is used for 2-point touch detection. It serves as pointer of the lock up table used for x-axis
2-point distance calculation. PX may be set to 0 when SPX is 1because the x-axis 2-point distance becomes 0.
PX = ByteH * 4 + ByteL / 64 (In the case of SPX=0)
PX = 0
(In the case of SPX=1.)
Y 2-point touch parameter: It is used for 2-point touch detection. It serves as pointer of the lock up table used for y-axis
2-point distance calculation. PY may be set to 0 when SPY is 1 because the y-axis 2-point distance becomes 0.
PY = ByteH * 4 + ByteL / 64 (In the case of SPY=0)
PY = 0
(In the case of SPY=1)
Ghost parameter: It is a value for judging a touch position (the direction of inclination) at dual touch.
GH = ByteH * 16 + ByteL / 16 (In the case of SGH=0)
GH = (ByteH * 16 + ByteL / 16) - 4096(In the case of SGH=1)
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