Si7013EVB-UDP Si7013EVB-UDP-F960

Rev. 0.2

7

demo software avoids floating point numbers by using deci-units.

A deci-unit is one tenth of a unit. The Sensor_ReadHumidity() routine returns the humidity in deci-percent RH and

the Sensor_ReadTemperature() routine returns the temperature in deci-degrees Celsius. For example, 43.7

percent RH is 437 deci-percent RH. Likewise, 25.4 degrees Celsius is 254 deci-degrees Celsius.

The demo software uses equations that are derived from the equations in the Si7013 data sheet. The derived

equations are modified to use deci-units.

3.1.2.3. Power Management

The Power Management component is implemented in a single file called PowerManagement.c and contains the

routines, LPM_Enable_Wakeup() and LPM_Disable_Wakeup(), for entering and exiting low-power modes. These

routines configure which events will wake up the MCU from low-power mode (LPM).

The LPM() routine puts the MCU into the specified low-power mode. The MCU remains in the low-power mode

until one of the configured wake up events occurs. When the MCU wakes up, then the LPM() routine examines the

MCU registers to determine which event caused the wake up and sets the appropriate WakeUp global variable.

The LPM() routine then returns to the caller. The caller may examine the WakeUp global variables to find out which

event caused the wake up.

3.1.2.4. Real Time Clock

The Real Time Clock (RTC) component uses the SmaRTClock peripheral to wake up the MCU from low-power

modes.

The Real Time Clock component is implemented in a single file called SmaRTClock.c.

The Real Time Clock component contains the RTC_Read() and RTC_Write() routines for reading and writing RTC

registers. RTC registers are not MCU Special Function Registers (SFRs), but must be accessed indirectly using

the SFRs. The RTC_Read() and RTC_Write() routines perform the indirect reads and writes of the RTC registers.

The RTC timer can be read and written with the RTC_CapureTimer() routine and the RTC_SetTimer() routine. The

RTC timer is a 32-bit counter, which increments at a 32.768 kHz rate. The RTC timer continues to increment when

the MCU is in low-power mode.

The RTC_WriteAlarm() and RTC_ReadAlarm() routines allows RTC alarms to the written and read. When the RTC

timer value equals an alarm value, then an RTC alarm event occurs.

3.1.2.5. Tick Counter

The Tick Counter component provides delay and timeout capabilities.

The Tick Counter component is implemented in a single file called Tick.c.

Timer 2 is configured to interrupt once a millisecond. The timer 2 interrupt handler increments an unsigned 16-bit

variable named TickCounter. The tick counter wraps around about every 65 seconds.

The current value of the tick counter is obtained by calling TickCount(). Timeouts are implemented by calling

TickCount() to get a starting time and then repeatedly calling ElapsedTime() to get the number of milliseconds that

have elapsed since the starting time. The Delay() routine does not return until the specified number of milliseconds

have elapsed.

3.1.2.6. Port Match

The Port Match component changes the temperature scale between Celsius and Fahrenheit when the user

presses the SW1 button. In addition, the SW2 button switches the temperature readings between the internal

sensor and the external thermistor.

The Port Match component is implemented in a single file called PortMatch.c.

The SW1 button on the MCU board is connected to bit 0 of Port 0 (P0.0). This bit is high when the button is not

pressed, but when the button is pressed the bit goes low. The SW2 button is connected to bit1 of Port0 (P0.1).

The MCU is configured to generate a port match interrupt when P0.0 or P0.1 goes low. If the MCU is sleeping

when a button is pressed, then the port match event wakes up the MCU and the port match interrupt handler is

called.

When the interrupt handler detects that a button has been pressed, then the interrupt handler reconfigures the port

match to detect when the button is released. This prevents a large number of useless port match interrupts while

the button is held down.