Lecture IV Advanced Embedded Systems Software

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Lecture IV Advanced Embedded Systems Software

• RTOS Essentials II
• Re-entrant Code
• Semaphores and Resource Management
• RTOSLite a basic 8051 Implementation
• The RTOS/Application Interface
• Task Control Block and Stack Storage
• Switching Tasks Handling Interrupts
• Example Application Code

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Design Objectives/Specs for RTOSLite

• Create an RTOS with lt 256 Bytes of Control Store
• Minimal Overhead Just Use ScratchPad RAM
• Each task contained in single bank of registers
• Only 4 tasks (4 banks of registers)
• An always task to allow interrupts blocked
  by other tasks
• No task priorities first come, first served
• 1 MHz 8051 can do worst-case task switch in lt
  500 mS
• RTOS interface extensible same interface used
  for FullRTOS
• Basic Interrupt Handling for Int0 and Int1 pins
  and internal timers (2)
• No use of DPTR to simplify implementation only
  scratchpad RAM available as global memory to each
  task (If DPTR is used then it requires a
  semaphore to manage access)

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Macro Listing I for RTOSLite
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Macro Listing II for RTOSLite
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Macro Listing III for RTOSLite
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Macro Listing IV for RTOSLite
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NextTask the RTOSLite Scheduler
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RTOSLite Timer Interrupt Handler
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RTOSLite Very Basic Task Switching
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RTOSLite A Simple Application Example
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