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5.2 Design of Capacitive Touch User Interface

The capacitive touch sense interface was designed for use with the CY8C21534-24PVXI

PSoC MCU. The board was designed using PADS software according to touch button

layout specifications given by Cypress Semiconductor Corporation [8]. The layout of

the design can be seen in figure 16.

Figure 16: PADS Software Capsense Board Design. Screenshot [16].

The component layout is first designed with PADS Logic. All required components are

placed and connected accordingly. This design is then taken into PADS Layout, shown

in figure 16, which is where the traces and pads are added. It is in this step that the

touch pads and ground plates are designed according to the PSoC specifications. The

clearances are set for the milling, and the board is then milled on the machine. The

components are then soldered to the board, and it is ready for programming.

In the PSoC Design software five buttons were set up in the design to represent the

five days of the present week. The MCU itself was programmed using the cap sense

wizard within the PSoC Designer program. The pins were then routed to the external

pins of the MCU so that they could be routed to the cap sense pads on the board. The

software for the capacitive touch required very little configuration, as most of the

programming is done by the cap sense wizard and through the use of prewritten

libraries. The only code that is necessary is a check to see if the button has been

touched. This consists of one command for button scan [17, 35-36].

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