TSC2007-Q1
SBAS545 –SEPTEMBER 2011
www.ti.com
Touch Detect
The PENIRQ can be used as an interrupt to the host. RIRQ is an internal pull-up resistor with a programmable
value of either 50kΩ (default) or 90kΩ. Write command '1011' (setup command) followed by data '0001' sets the
pull-up to 90kΩ. NOTE: The first three bits must be '0's and the select bit is the last bit. To change the pull-up
back to 50kΩ, issue write command '1011' followed by data '0000'.
An example for the Y-position measurement is detailed in Figure 27. The PENIRQ output is pulled high by an
internal pull-up. While in power-down mode with PD0 = 0, the Y– driver is on and connected to GND, and the
PENIRQ output is connected to the X+ input. When the panel is touched, the X+ input is pulled to ground
through the touch screen, and the PENIRQ output goes low because of the current path through the panel to
GND, initiating an interrupt to the processor. During the measurement cycle for X-, Y-, and Z-position, the X+
input is disconnected from the PENIRQ pull-down transistor to eliminate any pull-up resistor leakage current from
flowing through the touch screen, thus causing no errors.
In addition to the measurement cycles for X-, Y-, and Z-position, commands that activate the X-drivers, Y-drivers,
and Y+ and X-drivers without performing a measurement also disconnect the X+ input from the PENIRQ
pull-down transistor, and disable the pen-interrupt output function, regardless of the value of the PD0 bit. Under
these conditions, the PENIRQ output is forced low. Furthermore, if the last command byte written to the
TSC2007-Q1 contains PD0 = 1, the pen-interrupt output function is disabled and cannot detect when the panel is
touched. In order to re-enable the pen-interrupt output function under these circumstances, a command byte
must be written to the TSC2007-Q1 with PD0 = 0.
When the bus master sends the address byte with the R/W bit = 0, and the TSC2007-Q1 sends an acknowledge,
the pen-interrupt function is disabled. If the command that follows the address byte contains PD0 = 0, then the
pen-interrupt function is enabled at the end of a conversion. This action is approximately 100μs (12-bit mode) or
50μs (8-bit mode) after the TSC2007-Q1 receives a STOP/START condition, following the receipt of a command
byte (see Figure 31 and Figure 30 for further details about when the conversion cycle begins).
In both cases previously listed, it is recommended that whenever the host writes to the TSC2007-Q1, the master
processor masks the interrupt associated to PENIRQ. This masking prevents false triggering of interrupts when
the PENIRQ line is disabled in the cases previously listed.
Connect to
Analog Supply
VDD/REF
PENIRQ
VDD
RIRQ
Y+
X+
Pen Touch
Control
Logic
High when
the X+ or Y+
driver is on.
Sense
GND
Y-
High when the X+ or Y+
driver is on, or when any
sensor connection/short-
circuit tests are activated.
ON
Vias go to system analog ground plane.
GND
GND
Figure 27. Example of a Pen-Touch Induced Interrupt via the PENIRQ Pin
20
Submit Documentation Feedback
Copyright © 2011, Texas Instruments Incorporated
Product Folder Link(s): TSC2007-Q1
TI [ TEXAS INSTRUMENTS ]
