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two external structures have other functions too. We will see these properties when will discuss the
source file. Next, we have to define how many capacitive touch sensors are there in our design. Finally,
we have to set which hardware combination to use. In our case, Timer0_A, watchdog timer and digital
I/O’s PinOsc functionality are used to implement capacitive touch. The rest of the file is not needed to
be changed anywhere.
// Middle Element on the LaunchPad Capacitive Touch BoosterPack
extern const struct Element middle_element;
// One Button Sensor
extern const struct Sensor one_button;
//****** RAM ALLOCATION ********************************************************
// TOTAL_NUMBER_OF_ELEMENTS represents the total number of elements used, even if
// they are going to be segmented into seperate groups. This defines the
// RAM allocation for the baseline tracking. If only the TI_CAPT_Raw function
// is used, then this definition should be removed to conserve RAM space.
#define TOTAL_NUMBER_OF_ELEMENTS 1
// If the RAM_FOR_FLASH definition is removed, then the appropriate HEAP size
// must be allocated. 2 bytes * MAXIMUM_NUMBER_OF_ELEMENTS_PER_SENSOR + 2 bytes
// of overhead.
#define RAM_FOR_FLASH
//****** Structure Array Definition ********************************************
// This defines the array size in the sensor strucure. In the event that
// RAM_FOR_FLASH is defined, then this also defines the amount of RAM space
// allocated (global variable) for computations.
#define MAXIMUM_NUMBER_OF_ELEMENTS_PER_SENSOR 1
//****** Choosing a Measurement Method ****************************************
// These variables are references to the definitions found in structure.c and
// must be generated per the application.
// possible values for the method field
// OSCILLATOR DEFINITIONS
//#define RO_COMPAp_TA0_WDTp 64
#define RO_PINOSC_TA0_WDTp 65
Now it is time to explain the structure source file.
const struct Element middle_element =
{
.inputPxselRegister = (uint8_t *)&P2SEL,
.inputPxsel2Register = (uint8_t *)&P2SEL2,
.inputBits = BIT4,
// When using an abstracted function to measure the element
// the 100*(maxResponse - threshold) < 0xFFFF
// ie maxResponse - threshold < 655
.maxResponse = (450 + 655),
.threshold = 450
};
PxSEL and PxSEL2 bits internally set PinOsc feature. Since this example demonstrated one capacitive
touch button only one element is connected to BIT4 of port P2. Optionally, we can set the threshold
limit on which we can positively identify a touch.
// One Button Sensor
const struct Sensor one_button =
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