TSC-34/RU User’s Guide
1-3. Peripheral Composition Overview
A resistive touch screen is operated by resistance sensitive system between two layers such as film or glass. Two pieces of transparent materials with conductive coating are placed in the same direction as two electrodes face each other. The touch screen is activated when these transparent conductive layers are pressed to contact each other with a finger or a pen. The one of these conductive layers functions as an X-coordinates electric circuits and the other as a Y-coordinates circuits. To measure the X-coordinates TSC-34/RU supplies voltage, Vcc to the one of X-coordinates electrodes with GND to the other. When the touch screen is pressed under this environment the voltage of the X-coordinates resis- tance is detected by the Y-coordinates electrode (A_in) at the input point (x1), where the X-Y coordinate resistance layers make contact. The detected voltage in supply side is higher than the GND side, which means ‘A_in’=Vcc at the point ‘E’ and ‘A_in’=0(*1) at the point ‘A’. TSC-34/RU calculates coordinates data starting from A/D conversion of the ‘A_in’ voltage. The Y-coordinates is measured in the same way. By repeating this process alternately, coordinate value at the input point is determined.
(*1) Excluding the loss in the controller circuits and touch screen. Actual detected voltage should be lower than ‘Vcc - GND’ because of loss happened in the circuitry.
X-resistive-layer (reverse side)
X electrode | xl |
(reverse side) | |
Vcc = 5.0V
xl | A_in | Output Data |
A | 0V | 0000h (Min.) |
B | 1.25V | 00FFh |
C | 2.5V | 01FFh |
Y-resistive-layer 
Y electrode
D | 3.75V | 02FFh |
E | 5V | 03FFh (Max.) |
| | | | | A_in | |
| | | | | (TSC-34/RU) | |
| (Touch Screen) | | Touch | xl | Vcc | |
| | | 232C/USB)-(RS |
| X-resistive-layer | | | | (TSC-30/IC) |
| | | | |
| | | | | |
| Y-resistive-layer | | | | A_in | To host |
| | | | |
| | | | | |
E | D | C | B | A | | |
Document No. DER-S0017A | 3 | Rev.1.1 ©2008 DMC Co., Ltd. |