Time Complexity: LCD display (16x2) with I2C backpack
O(n)
0
0
LCD display (16x2) with I2C backpack in Raspberry Pi - Time & Space Complexity
Understanding Time Complexity
When working with an LCD display using an I2C backpack on a Raspberry Pi, it's important to understand how the time taken to update the display changes as the amount of data grows.
We want to know how the program's running time changes when we write more characters to the screen.
Scenario Under Consideration
Analyze the time complexity of the following code snippet.
from smbus2 import SMBus
import time
bus = SMBus(1)
address = 0x27
def write_string(string):
for char in string:
bus.write_byte(address, ord(char))
time.sleep(0.01)This code sends each character of a string one by one to the LCD via I2C, pausing briefly after each character.
Identify Repeating Operations
Identify the loops, recursion, array traversals that repeat.
- Primary operation: Loop over each character in the string to send it via I2C.
- How many times: Once for every character in the input string.
How Execution Grows With Input
As the string gets longer, the number of I2C write operations grows directly with the number of characters.
| Input Size (n) | Approx. Operations |
|---|---|
| 10 | 10 writes + 10 pauses |
| 100 | 100 writes + 100 pauses |
| 1000 | 1000 writes + 1000 pauses |
Pattern observation: The time grows steadily and directly with the number of characters sent.
Final Time Complexity
Time Complexity: O(n)
This means the time to send data to the LCD increases in a straight line as the number of characters grows.
Common Mistake
[X] Wrong: "Sending one character or one hundred characters takes the same time because the I2C bus is fast."
[OK] Correct: Each character requires a separate write operation and a small delay, so more characters mean more time spent.
Interview Connect
Understanding how hardware communication time grows with data size helps you write efficient code and explain your design choices clearly.
Self-Check
"What if we removed the delay after each character? How would the time complexity change?"