Analog Touch Panel
The Analog Touch Panel is mounted over the LCD Display PWBA. As shown in
touch panel is connected to the UI Base PWBA via the Key/LED PWBA by four analog input/
output lines. The LCD Display Microcontroller on the UI Base PWBA alternately samples the
touchscreen's X dimension and its Y dimension. These samples alternate rapidly enough that
when the user presses the touchscreen, at least one X dimension measurement and at least
one Y dimension measurement are taken.
Reissue
DocuColor 12/DCCS50
The LCD Display Microcontroller takes a Y dimension measurement by driving the Y dimen-
sion lines (Up and Down) as outputs and accepting the Right X dimension line as an input.
Figure
1, the
When used as an output, the Up output is grounded and a Down output is at about +5 VDC.
When the panel is touched, two internal conductive layers make contact. The voltage at the
Right input is proportional to the Y position where the touch occurred.
The X dimension input is taken in a similar fashion. The LCD Display Microcontroller drives the
X dimension lines and samples the Up line as an input. When driven, Right is at ground and
Left is at about +5 VDC.
Figure 1 Analog Touchscreen Interconnect Block Diagram
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Principles of Operation
Analog Touch Panel