SGDRS Software System Design Justin A. King WWU EET Senior project 2013

H ARDWARE R ESOURCES MCU – MSP430G2553 available resources Memory 512B RAM / 16KB ROM 2x 16 bit Timer modules, TA0 and TA1 14 GPIO pins Up to 16MHz bus speed Used resources Memory 6 bytes pf RAM / 1KB ROM Both 16 bit Timer modules, TA0 and TA1 3 GPIO pins 1MHz bus speed (lower power)

B ASIC OVERVIEW The program functions as follows Initialize the GPIO Initialize the Timers Go into LPM3 When TA0ISR verifies that output should happen, it wakes the CPU up FOREVER() IOTask() Enter LPM3 (until P1ISR wakes the CPU up again)

K ERNEL Interrupt driven Kernel No specific timing requirements No time slice execution No task pre-emption RTC Period 1 second Tasks and ISRs StartTask(), IOTask() TA0 int, TA1 int, P1 int

S TART T ASK () Used to start the clocks and set up interrupt pins Utilizes IO initialize functions from IO module Sets up Input and Output pins Sets up a tie down resistor for the PIR sensor so it is not left floating Utilizes Timer initialize functions from timer module Sets up the kHz crystal for RTC timer, TA0 Sets up parameters for TA1 PWM generation Execution time: ~1ms Period: once (at start-up)

IOT ASK () Handles mostly output functionality Checks to see if the spray flag is set by the TA0ISR If the flag is set, the output pin that drives the FET that is attached to the servo is set Changes output phase to adjust PWM pulse width for the TA1ISR Execution time: Up to 2s Waits for the servo to turn for half a second and then turns it back Period: Sporadic (occurs when P1ISR wakes the program up from LPM3)

TA0ISR Functions as the RTC timer for the program Uses the kHz crystal Clock dividers provide a 1s periodic interrupt On interrupt, it increments a variable SecCount After 3600 seconds, HourCount is incremented If HourCount > 24, a SprayFlag is set Execution time: <3us Period: Periodic, every 1s

TA1ISR Used to generate the PWM signal for the servo control Uses continuous mode timer and adjusts the interrupt period to produce the PWM signals Produces servo_down and servo_up signals PWMs with different duty cycles Depends on the phase that is set by IOTask() Execution Time: <2us Period: Sporadic (once a day)

P1ISR Handles the PIR sensor input functionality Triggers when a pin on port 1 transitions from logic low to logic high Checks the spray flag from TA0ISR If the spray flag is set, it wakes the CPU up from LPM3 Execution time: ~2us Period: Sporadic (occurs when PIR is tripped)

M ODULES ModuleTasksPublic Functions main.cStartTask() IO.cIOTask()IOInit() Timer.cRTCTimerInit() CheckSprayFlag() ClearSprayFlag()