Datasheet

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6.4 Program Description
Kit Operation
After the TSC2003EVM-PDK software installation (described in Section 6.2 ), evaluation and development
with the TSC2003 can begin.
6.4.1 Touch Screen Functions Panel
The touch screen box in this panel will be updated when a touch is detected on the touch screen. As the
touch screen is drawn upon, the motion on the touch screen will be translated into pixels on this box. The
software takes X, Y, and Z readings which are shown to the right of the touch screen box. As the touch
pressure is increased, the pixel size increases; a lighter touch results in smaller pixel sizes.
The Z-value displayed is not what is described in the TSC2003 data sheet, because in the data sheet
equation, it is assumed that the sheet resistance of the touch screen being used is known. The value used
in this program is calculated by Equation 2 of the TSC2003 data sheet, but without multiplying it by the
R
X-plate
resistance. This value ranges from 0 to 3, and larger, with smaller numbers representing a more
forceful press on the screen. Using the Maximum Z Value to Display knob, you can set a threshold so
that the program does not display lightly pressed points. This threshold setting helps to eliminate display
of spurious points that may result from touch screen mechanical bouncing.
The display can be cleared by pressing the Clear Graph button on the screen.
6.4.2 Data Acquisition Functions Panel
The TSC2003 has provision for measuring two battery voltages (VBAT1 and VBAT2), two auxiliary input
voltages (AUX1 and AUX2), and temperature. This panel displays the measured values for these
parameters. Measurements are updated only when the touch screen is not being pressed.
Temperature is displayed using both methods described in the TSC2003 data sheet. Using the TEMP0
and TEMP1 measurements, a temperature reading with 2 ° C resolution and accuracy is achieved. Using
only the TEMP0 measurement, a reading with 0.3 ° C resolution is possible, but this option requires
knowing the TEMP0 value at +25 ° C; this would normally be a calibration that the user would perform. This
program assumes that TEMP0 = 600mV at +25 ° C.
6.4.3 Configuration Panel
The TSC2003 can be configured to operate in 8-bit or 12-bit resolution modes. Control over the mode
used is selected in this panel.
In the middle of this panel is an indicator light that shows the I
2
C Bus Status. If the TSC2003 is
acknowledging the address sent, the light is green; if the TSC2003 cannot acknowledge, the light is red.
The address that the TSC2003 is set to is shown in binary format in the box labeled, Device Address
A1-A0. The address set here should correspond to the bit settings determined by JMP3 and JMP4 on the
TSC2003EVM.
The two power-down bits of the TSC2003 can be set from this panel as well. A brief description of the
mode selected is shown on the screen when setting these bits; see Table II ( Power-Down Bit Functions)
of the TSC2003 data sheet for details on what these bits do.
6.4.4 Datalogging
The software can record the data it takes from the TSC2003 to a tab-delimited file, suitable for importing
into spreadsheets. To do this, first go into the File menu, and select Log Data to File..., which opens a
file-select window and allows you to specify a file to which to write the data. At the same time, this enables
the Datalogging menu.
When ready to begin recording data to a file, select Datalogging → Start Logging. Data is written to the file
until Datalogging → Stop Logging is selected. When the screen is not touched, the VBAT1, VBAT2,
AUX1, AUX2 and TEMP values are written to the file, and the X, Y, Z1, and Z2 parameters are written to
the file with values of 9999, to indicate that they are not updated. When the screen is touched, the X, Y,
Z1, and Z2 parameters are written while the VBAT1, VBAT2, AUX1, AUX2 and TEMP values are written
to the file as 9999. Because the program constantly updates at a rate of about 400 readings per second,
datalog files can quickly grow large; therefore, log only that data which is necessary.
TSC2003EVM and TSC2003EVM-PDK User's GuideSBAU109 – March 2005 9