53. Compile-Time Timer Reload

In many microcontrollers, periodic interrupts (1 ms, 10 ms, 100 ms, etc.) are generated using a hardware timer reload value.

This value must be computed using:

reload = timerClockHz × intervalSec

Since this value must be exact, firmware often computes it at compile time using constexpr.
Incorrect reload values cause jitter, drift, or system failure.

Your job is to compute the correct timer reload count at compile time for different timer intervals.

What you must do:

• Define a constexpr function named computeReload
  • It must compute:

    • (clockHz × intervalMs + 500) / 1000 

• This converts milliseconds to seconds
• +500 is used for integer rounding
• Define a constexpr array named RELOAD_TABLE
  • It must contain exactly 3 compile-time reload values, in this order:
    1. Reload value for 1 ms
    2. Reload value for 10 ms
    3. Reload value for 100 ms
• All values must be computed using computeReload
• Use:
  • timerClockHz = 1'000'000 (1 MHz)

Program input:

• The user enters an integer index:
  • 0 → 1 ms reload
  • 1 → 10 ms reload
  • 2 → 100 ms reload
• Input is guaranteed to be valid (0–2)

Program output:

• Print the reload value from RELOAD_TABLE[index]

Example 1

Input:

1

Output:

10000

Example 2

Input:

2

Output:

100000

Constraints:

• computeReload must be declared constexpr
• RELOAD_TABLE must be declared constexpr
• No runtime math except array indexing
• Use integer arithmetic only
• Output must match exactly