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Exercise 2: Productivity Timer (ProTimer)

Overview

The application that tracks your productive working time.

Requirements

1. + button increments time (minute-level increment).

2. - button decrements time (minute-level decrement).

3. Start/Pause button starts or pauses the countdown, or shows STAT if pressed together.

4. When the countdown is paused, time can be modified.

5. Press the + and - button simultaneously to abort the running timer.

6. Application must beep 20 times when it returns to IDLE mode.

7. When the application is in IDLE mode, pressing the Start/Pause button should show the STAT for 1 sec and auto return to IDLE mode.

Components

• Arduino Uno board

• 1, 5mm LED

• Jumper wires

States

• IDLE

• TIME_SET

• PAUSE

• COUNTDOWN

• STAT

Events

Extended State Variables

• The variables that appear on the state machine to be used for storing various data and making decisions.

  • curr_time : uint32_t

  • elapsed_time : uint32_t

  • pro_time : uint32_t

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  /* The main application structure */
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  typedef struct protimer_tag
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  {
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      uint32_t curr_time;     // Stores the time user has set
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      uint32_t elapsed_time;  // Number of seconds that has elapsed
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      uint32_t pro_time;      // Productive time spent by the user
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      ...
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  } protimer_t;
  

• A structure that contains these types of variables is also called as "main application structure".

Data Structures

• Define various signals of the application using enum

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  /* main.h */
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  /* Signals of the application */
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  typedef enum {
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      INC_TIME,
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      DEC_TIME,
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      TIME_TICK,
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      START_PAUSE,
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      ABRT,
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      /* Internal activity signals */
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      ENTRY,
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      EXIT
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  } protimer_signal_t;
  

• Define various states of the application using enum

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  /* main.h */
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  /* States of the application */
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  typedef enum {
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      IDLE,
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      TIME_SET,
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      COUNTDOWN,
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      PAUSE,
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      STAT
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  } protimer_state_t;
  

• Define the main application structure

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  /* main.h */
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  /* Main application structure */
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  typedef struct {
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      uint32_t curr_time;
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      uint32_t elapsed_time;
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      uint32_t pro_time;
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      protimer_state_t active_state;
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  } protimer_t
  

• Define structures to represent events

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  /* main.h */
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  /* User generated events */
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  typedef struct {
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      uint8_t sig;
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  } protimer_user_event_t;
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  /* Tick events */
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  typedef struct {
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      uint8_t sig;
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      uint8_t ss;     /* Sub-seconds */
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  } protimer_tick_event_t;
  

  Or, you could improve this code by introducing the OOP concept. (Using structure embedding)

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  /* main.h */
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  /* Generic (supter) event structure */
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  typedef struct {
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      uint8_t sig;
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  } event_t;
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  /* User generated events */
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  typedef struct {
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      event_t super;
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  } protimer_user_event_t;
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  /* Tick event */
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  typedef struct {
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      event_t super;
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      uint8_t ss;     /* Sub-seconds */
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  } protimer_tick_event_t;
  

   

State Machine

Flat State Machine

Implementation