Generating precise delays with timers in Embedded C - Step-by-Step Execution

Concept Flow - Generating precise delays with timers

Configure Timer

↓

Start Timer

↓

Timer Counts

↓

Check if Timer Reached Delay

↓

Stop Timer

↓

Delay Complete

The timer is set up and started, then counts until it reaches the desired delay, after which it stops and signals completion.

Execution Sample

Embedded C

void delay_ms(int ms) {
  timer_init();
  timer_start();
  while(timer_count() < ms) {}
  timer_stop();
}

This function creates a delay of 'ms' milliseconds by starting a timer and waiting until the timer count reaches 'ms'.

Execution Table

Step	Action	Timer Count (ms)	Condition	Result
1	Initialize timer	0	N/A	Timer ready at 0 ms
2	Start timer	0	N/A	Timer counting begins
3	Check timer count	0	0 < ms	Continue waiting
4	Check timer count	1	1 < ms	Continue waiting
5	Check timer count	2	2 < ms	Continue waiting
...	...	...	...	...
n-1	Check timer count	ms-1	ms-1 < ms	Continue waiting
n	Check timer count	ms	ms < ms is False	Exit loop
n+1	Stop timer	ms	N/A	Timer stopped, delay complete

💡 Timer count reached the desired delay value, loop exits and timer stops

Variable Tracker

Variable	Start	After 1	After 2	After n-1	After n	Final
timer_count	0	1	2	ms-1	ms	ms
delay_ms (input)	ms	ms	ms	ms	ms	ms

Key Moments - 2 Insights

Why does the loop check 'timer_count() < ms' instead of 'timer_count() <= ms'?

Because the loop must exit when timer_count equals ms, so the condition is false at that point, stopping the delay exactly at ms (see execution_table row n).

What happens if the timer is not stopped after the delay?

The timer would keep running, possibly causing incorrect timing later. The stop action (execution_table row n+1) ensures the timer resets for next use.

Visual Quiz - 3 Questions

Look at the execution_table at step 3, what is the timer count and condition result?

A Timer count is 1, condition true (continue waiting)

B Timer count is 0, condition true (continue waiting)

C Timer count is 0, condition false (exit loop)

D Timer count is 1, condition false (exit loop)

💡 Hint

Refer to execution_table row 3 for timer count and condition

At which step does the timer stop according to the execution_table?

A Step n+1

B Step n

C Step 1

D Step 2

💡 Hint

Look at the action column in execution_table row n+1

If the condition was changed to 'timer_count() <= ms', when would the loop exit?

A When timer_count is ms

B Immediately at 0

C When timer_count is ms+1

D Never exits

💡 Hint

Consider that '<=' allows the loop to continue while timer_count equals ms (see condition logic in execution_table)

Concept Snapshot

Generating precise delays with timers:
- Initialize and configure timer
- Start timer counting
- Loop while timer count < desired delay
- Stop timer when delay reached
- Ensures accurate timing
- Always stop timer to reset for next use

Full Transcript

This visual execution shows how to create precise delays using timers in embedded C. First, the timer is initialized and started. Then the program checks the timer count repeatedly until it reaches the desired delay in milliseconds. Once the timer count equals the delay, the loop exits and the timer is stopped. This method avoids inaccurate delays caused by simple loops and ensures precise timing. Key points include checking the condition correctly and stopping the timer after the delay completes.