# C++ Timer System for NTUR
###### tags: `firmware_hardware` `electrical_system` `NTURT`

## Introduction
The **C++ Timing System for NTUR** is designed to be a pure C++ based firmware infratructure to imlement a versatile solution on the racecar's firmware. The purpose of this design is to replace FreeRTOS in order to avoid the flaws of RTOS, such as:
- Multiple tasks may write the same variable during runtime, leads to confliction
- Difficult to debug and find problems of your code, since RTOS is not based on a line-by-line operation logic
- Complex hardware & firmware settings may confuse new-learners, such as **mutexs**, **kernel settings**, **memory**, ...

Instead of running as multiple threads in RTOS, tasks (ex. CAN communication, dashboard, APPS, ...) in the **C++ Timing System for NTUR** runs in a ==**function-based priority queue**==
In simple words, each task is represented by one function, and **C++ function object** can maniluplate the functions as objects, and further manage their precedence in a **priority queue** storing the function objects and run them in a order

## Prerequisite
There are few intermediate C++ concepts required to understand how the **C++ Timer System for NTUR** works, the topics of background knowledge you should have in advance are listed below:
### STL Libraries
### Function Object
### Timing
We use the `<chrono>` header in C++, it provides a powerful and versatile way to measure and manipulate time intervals, essential concepts of `chrono` are introduced below
#### Basic elements
- Clocks
Represent the source of time measurements. The `<chrono>` library offers three primary clock types:
- `std::chrono::system_clock`
Retrieves the system's wall-clock time

- `std::chrono::steady_clock`
Provides a monotonic (always increasing) time source, unaffected by system time changes. It's suitable for measuring elapsed time during code execution.

- `std::chrono::high_resolution_clock`
Offers the highest possible resolution for time measurements on the current system. It's ideal for very precise timing needs.

- Time points
Represent specific moments in time obtained from a particular clock. You can use `std::chrono::time_point` to capture the current time from a chosen clock

- Durations
Represent the elapsed time between two time points. You can calculate the duration between two time_point objects using `std::chrono::duration_cast`