CRS1 ETC-unknow, CRS1 Datasheet - Page 11

• Manufacturer Part Number: CRS1
• Description: An Analog Touch Panel Controller Chip Through Serial Crs1-656 ,ps/2 Crs1-685
• Manufacturer: ETC-unknow

11. Other Functions
(1) Calibration
I. Auto-Calibration
Vref 2
Vref 1
Key Area
Wiring Section
Wiring Section
Illustration : Equivalent Circuit of Touch Panel
Generally, touch panels have an equivalent circuit as the illustration above shows.
When a DC voltage is applied to both terminal ends of the touch panel, the total voltage
drop across the circuit is equal to the sum of the voltage drops of a key area and both wiring
sections. Each voltage drop will vary when any resistance varies. It means that a position
shift on the monitor will occur even on the same point to be pressed if any resistance changes.
On the contrary, the combination of the controller and a 8-wire touch panel has an
auto-calibration function which eliminates the resistance of both wiring sections by reading
reference voltage, such as Vref 1, Vref 2. Those reference data are detected when powering on,
sending reset command(only in serial communication), or returning from Stop Mode, and
stored in the controller memory during powering on. After those processes, the controller
generates data which are adjusted from 0 to 1023 over the key area. Therefore, you can get
very stable data in various environmental conditions for a long period of time in use.
Difference between 4-wire touch panel and 8-wire touch panel
[ 4 wires Touch Panel
]
x L
x R
y U
y L
The controller outputs the digital position data converted from the analog voltage of the
pressed position. For example, when the analog voltage of the pressed point is 2(V) for
applying 5(V) to the terminals, “409” is the outputted data. 2(V) / 5(V) x 1023 = 409
11
SPEC 8.2.00