Datasheet

Circuit Description
3-6
Table 3-9.Touch Screen Input
Reference
Designator
Description
Pin
Number
Signal
Name
Function
1 X- Touch screen X- electrode
2 Y+ Touch screen Y+ electrode
J12, J13 Touch screen input
3 X+ Touch screen X+ electrode
4 Y- Touch screen Y- electrode
3.2.9 Analog Input Connector
The auxiliary and battery inputs to the touch screen controller are brought onto
the motherboard through a terminal block, J14. The pinout is shown in
Table 3-10.
Table 3-10.Analog Input Connector
Reference
Designator
Description
Pin
Number
Signal
Name
Function
1 VBAT1 Battery input 1, 0 V to 6 V
Battery and auxiliary inputs to
2 VBAT2 Battery input 2, 0 V to 6 V
J14
Battery and auxiliary inputs to
the touch screen control
3 AUX1 Auxiliary input 1, 0 V to VREF
4 AUX2 Auxiliary input 2, 0 V to VREF
3.3 Circuit Description
The TSC2301 evaluation kit circuitry consists of a USB interface and
microprocessor, power supply circuitry, touch screen and analog input
interfaces, a keypad interface, an LCD bias D/A converter circuit, and audio
interface circuitry (both analog and digital). These circuits are described in the
following sections.
3.3.1 USB Interface and Microprocessor
The TSC2301EVM has a USB interface for connecting to a PC. This
connection is made through a TAS1020B streaming audio processor, U4.
The SPI interface to the TSC2301 can be controlled from two sources: the
external SPI header, J11, or through the onboard microprocessor (U4) via
USB. U4’s outputs are enabled only when the supplied firmware is loaded. The
firmware resides in serial EEPROM chip U3. U4 only loads firmware from U3
when U3’s A1 address line is pulled low. To disable firmware loading, A1 must
be high, by having JMP6 removed.
When the firmware is loaded and active, D2 (a yellow LED) lights.
If no firmware is loaded, U4’s outputs are in 3-state, allowing the external SPI
bus to drive the TSC2301. When the firmware is loaded, the PC software
enables the microprocessor to control the SPI bus.