AN957 Datasheet, PDF (23/25 Pages) List of Unclassifed Manufacturers – Measuring HEXFETCharacteristics

AN957: TouchXpress™ Configuration and Profiling Guide
Example Development Workflow
4.4 Step 4 — Fly-Wire Proof of Concept
In many cases, the next stage of development involves using a product mock-up, possibly with a host processor running other system
components that will all be integrated onto a single PCB in later development stages. At this stage, it is likely that the on-board sensing
electrodes on the TouchXpress evaluation board will be replaced by copper tape stuck to product mock-up overlays or a case.
The evaluation board can continue to be used in this stage of development to analyze the prototype system. Each sensor input pin is
accessible through a row of vias found on the evaluation board. Each via has a corresponding zero ohm resistor that shorts the device
input pin to the corresponding sensing electrode. Removing that zero ohm resistor disconnects the sensor input pin from the sensing
electrode. The user can then solder a wire into the sensor input’s via, fly that wire to a copper tape-implemented sensor, and solder the
other end of the wire to the copper tape.
Figure 4.5. Connecting External Sensing Electrodes on a TouchXpress Evaluation Board
If the mock-up uses a host MCU, that MCU may want access to the TouchXpress device’s output pins. For the CPT007B, the host
MCU would need access to the OUT pins corresponding to each input sensor. For the CPT112S, the host MCU would need access to
the device’s I2C pins and the device’s interrupt pin. All of these signals are available through the evaluation board's side-edge expan-
sion (EXP) header. A schematic included with the board’s user guide provides a pinout for this connector.
4.5 Step 5 — Checking Mock-Up Performance
The [Capacitive Sense Profiler] tool can be used at this point to check whether touch deltas with the copper tape have changed dra-
matically relative to the touch deltas seen on the TouchXpress evaluation board. If touches cause a touch delta that is greater than 10%
of the previously-configured touch delta, switch back to [Xpress Configurator] and adjust the deltas accordingly.
The interface requirements between the TouchXpress device and the host MCU may require additional configuration changes. For the
CPT007B, the OUT pin drive strength can be switched to open-drain output if the interfacing MCU requires 5 V logic with pull-ups. The
polarity of the OUT pins can also be switched between active high and active low, depending on host MCU requirements. For the
CPT112S, the I2C address may need to be changed from its default value of 0xE0, if the device will be connected to a bus with another
device that has a conflicting address.
4.6 Step 6 — Interfacing with Prototype Boards
When the development reaches a point where prototype boards are being created, perform in-system configuration and data analysis
through Simplicity Studio by routing the TouchXpress device Config Data and Config Clk pins to vias on the prototype board.
A separate ToolStick Debug Adapter board can also be wired into those vias to maintain a link with [Xpress Configurator] and [Capac-
itive Sense Profiler]. The programming guide AN949: TouchXpress™ Programming Guide can be used for reference on how to con-
nect a ToolStick Debug Adapter to a prototype board.
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