Controlling lots of stuff

Some references

• Embedded Systems WIKIBOK
• Embedded C and the 8051
• Programming Embedded Systems I

The super loop

Traditional

void main(void) {
  Initialize1();
  Initialize2();
  ...
  Initializen();
  while(1) {
    Work1() ;
    Work2() ;
    ...
    Workn();
  }
}

Arduino

void setup() {
  Initialize1();
  Initialize2();
  ...
  Initializen();
}

void loop() {
  Work1() ;
  Work2() ;
  ...
  Workm();
}

Problems

• Might be a lot of things in the loop
• Time through the loop may be hard to figure
• Some activities are more important than others
• Some activities are much more frequent than others
• Activities may depend on the state
• Some activities have delays
• May use power
• May not be very modular

How about music or PWM

• In a subloop?
• Calling analogWrite() -- if available
• Checking the time in the super loop
• Call delay

Interrupts and Timers

Arduino examples

• AttachInterrupt()
• Timers

But be very careful. This is complicated stuff.

• Secrets of Arduino PWM
• Mastering timer interrupts on the Arduino
• Arduino, Interrupts and Timers
• ATmega datasheet (sections 15 to 18)

Alternatives

Think about using a linked list of things to be done. These are common in read operating systems.

Operating systems

Services of the operating system

• Create tasks/threads/tasklets
• Synchronize threads
• Manage memory
• Support "files" (on SD cards are in flash)
• See pthread API

The world of RTOS

• Arduino
  • X
  • X
  • X
• Big embedded systems
  • Embedded linux
    • Chumby hacker board
    • Android
  • Windows Embedded