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Humidity Sensing Fan Controller

Humidity Sensing Fan Controller. Jason Huft 05/11/10. General System Requirements. MCU: HC9S08QE32, 44 pin package Bus Frequency: approximately 50 MHz Internal clock source. Timeslice Kernel Timeslice Period: 100 ms Memory Available: 32k EEPROM 2k RAM Memory Requirement:

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Humidity Sensing Fan Controller

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  1. Humidity Sensing Fan Controller Jason Huft 05/11/10

  2. General System Requirements • MCU: HC9S08QE32, 44 pin package • Bus Frequency: approximately 50 MHz Internal clock source. • Timeslice Kernel • Timeslice Period: 100 ms • Memory Available: • 32k EEPROM • 2k RAM • Memory Requirement: • 8-10k EEProm • 2k RAM

  3. Timeslice Kernel Tasks • Startup Task • Push-Button Task • Display Task • Humidity Detect Task • Fan Control Task • Timing Task • WaitForSlice

  4. Start Task • Sets initial state of the system and initializes the registers. • Execution Time: • 100ms worst case. • Period: • Once at Startup

  5. Push-Button Task • Waits and recognizes a key press on a push-button switch.De-bounces the switch. • Period: 20ms (sporatic) • Execution Time: 10μs • Changes state from key press • Off • On (can recognize multiple presses of this key) • Automatic

  6. Humidity Detect Task • Observes changing voltage from the sensor • Converts the voltage into digital information • Passes voltage level as a hex output to the MCU. • Period 100ms • Execution Time 5μs

  7. Display Task • Writes information to LCD display • Takes timing information from timer task • Also reports current state if in On or Automatic State. • Period: 100ms • Execution Time: about 5ms.

  8. Fan Control Task • Interrupts information from the Humidity Detect Task to choose if the fan should be on/off in automatic state. • Calls fan activated/deactivate based on state. • Period: 20ms (sporadic) • Execution Time: 20us max (10 us average)

  9. Timing Task • Keeps track of remaining time in the on state. • Mostly internal clock. Receives information from Push-Button Task • Changes system state if certain conditions are met. • Period: 100ms • Execution Time: 20us or so

  10. Wait for Slice • Fills the remaining time in each slice period. • Included to assist in proper task timing and debugging. • Period: 100ms • Execution Time: Varies based on how many other tasks need to execute in one slice period.

  11. Modules

  12. CPU Load • Max CPU Load • 20us/100ms + 20us/20ms + 5ms/20ms + 10us/20ms + 5us/100ms = .05175 * 100 = 25.175% Max CPU load - 20us/100ms + 5ms/100ms + 10us/20ms + 5us/100ms = 5.12% average CPU Load

  13. Main Dataflow Diagram

  14. Dataflow Diagram: Continued

  15. AtD Converter Dataflow Diagram Humidity Detect Task A\D Converter A-to–D I/O pin Ts = 100ms ADCCFG AtDInit() AD0 ADP0 ADCSC1 HumidityRead() HumidityLevel

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