LED Display Panel

1
LED Display Panel

• System Software Design
• by Chan-Chia (James) Chang

2
General System Design

• MCU
• Motorola 9S12DP256B
• 24 MHz Bus Frequency
• 256K Byte Flash
• 12K Byte RAM
• 4K Byte EEPROM

3
Kernel Selection

• MicroC/OS-II
• Real-Time Preemptive Kernel

4
Priority of Tasks

• 4 Start Task
• 5 Clock Task
• 6 TrafficLight Task
• 7 LED Task
• 8 KeyPress Task

5
Start Task

• Initialize the system
• Priority 4
• Period run it only once
• Execution time 2ms

6
Clock Task

• Counts every second
• Priority 5
• Period 1sec, periodic
• Execution time 1us

7
TrafficLight Task

• Control traffic lights
• Priority 6
• Period 0.5sec, periodic
• Execution time 1us

8
LED Task

• Controls LEDs flash, and input data into LED
  drivers
• Priority 7
• Period 10ms, periodic
• Execution time 48us

9
KeyPress Task

• Determent if someone pushes the buttons
• Priority 8
• Period 10ms, periodic
• Execution time 2us

10
CPU Load

• Lmax 1us 1us 48us 2us
• 1s 0.5s 10ms 10ms
• Lmax 0.5
• Lavg 0.26

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Modules
Task Public Functions and Data
Main.c Start Task
Traffic.c TrafficLight Task Traffic()
PICDisp.c LED Task PICDisp()
LEDWrite.c LED Task LEDWrite()
KeyPress.c KeyPress Task KeyInit(), KeyPend()
Clock.c Clock Task Time()
12
Data Flow Diagram
Application
User
Display
Store Picture
Display
PICDisp.c
LED Display
LEDWrite.c
KeyPress.c
Display
Traffic.c
Traffic LEDs