3. "Wanli" Raspberry Pi car - Python learning (timing task)

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3. "Wanli" Raspberry Pi car - Python learning (timing task) [Copy link]

 

If you use Python to build a car project, then timing tasks are essential. There are four main methods for timing in Python.

1. Using sleep in while loop
2. Timer in threading module
3. sched module
4. Timing Framework APScheduler

There are many introductions on the Internet about the implementation and characteristics of the above four methods. The conclusion is that APScheduler is the best, and my main focus is on the accuracy of the timer and the shortest achievable timing.

Edit the following code (APScheduler package needs to be installed in advance), set the periodic timing to 1ms, and output the current time and time difference.

import time
import datetime
from apscheduler.schedulers.blocking import BlockingScheduler
pre_time=0;
def func():
global pre_time
now = time.time()
cha=now-pre_time
pre_time=now
print(now," ",cha)
scheduler = BlockingScheduler()
scheduler.add_job(func, 'interval', seconds=0.001, id='main')
scheduler.start()

It is found that errors are often reported during operation, and the time error is very large. The periodic timing is changed to 10ms, and the results are as follows.

There are no errors when running, but there is still an error of about ±3%. This error is also fatal in a project that requires real-time control, so using the timer in Python to do real-time timing tasks is a failure.

I think this is mainly related to the low efficiency of Python code execution. Linux itself is not a real-time operating system, which is also a reason.

question

Python is so bad at timers, so would C be better?

Source code

GitHub:

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Gitee:

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Summary of "Wanli" Raspberry Pi car:

lb8820265's "Wanli" Raspberry Pi car open source sharing - DIY/Open Source Hardware Zone - Electronic Engineering World - Forum (eeworld.com.cn)

Table of contents:

"Wanli" Raspberry Pi car launched

1. “Wanli” Raspberry Pi car - Establishing a project warehouse

2. "Wanli" Raspberry Pi car - Python learning (using Thonny)

3. "Wanli" Raspberry Pi car - Python learning (timing task)

4. "Wanli" Raspberry Pi car - C++ learning (compile and run, use geany)

5. "Ten Thousand Miles" Raspberry Pi Car - WiringPi Learning (Delay and Thread Simulation Timer)

6. "Wanli" Raspberry Pi car - wiringPi learning (PWM and external interrupt simulation timer)

7. "Ten Thousand Miles" Raspberry Pi Car——RPi.GPIO Learning (PWM and External Interrupt Simulation Timer)

8. "Wanli" Raspberry Pi car - socket learning (local communication)

9. "Ten Thousand Miles" Raspberry Pi Car - Socket Learning (TCP Two-Machine Communication)

10. "Ten Thousand Miles" Raspberry Pi Car - Socket Learning (UDP Two-Machine Communication)

11. "Wanli" Raspberry Pi car - socket learning (sent from Android)

12 "Wanli" Raspberry Pi car - socket learning (Android sending and receiving)

13. "Wanli" Raspberry Pi Car - Accessories Preparation

14 "Wanli" Raspberry Pi car - motor drive learning

15 "Wanli" Raspberry Pi car - photoelectric encoder learning (forward and reverse judgment)

16. "Wanli" Raspberry Pi car - photoelectric encoder learning (obtaining speed)

17 "Ten Thousand Miles" Raspberry Pi Car——VSCode Learning (Compiling and Debugging)

18. "Ten Thousand Miles" Raspberry Pi Car——Makefile Learning

19 "Ten Thousand Miles" Raspberry Pi Car——VSCode Learning (Multiple C File Link Debugging)

20 "Million Miles" Raspberry Pi Car - Motor Control Learning (Control Speed)

21. "Wanli" Raspberry Pi car - motor control learning (4-wheel speed control)
22. "Wanli" Raspberry Pi car - mobile phone remote control motor rotation

23 "Wanli" Raspberry Pi car - connected to Raspberry Pi without screen

24 "Millions" Raspberry Pi Car - Bullseye Benchmark Test of Raspberry Pi 64-bit System

25 "Million Miles" Raspberry Pi Car - Nam Wheel Control

26 "Wanli" Raspberry Pi car - program startup

27 "Ten Thousand Miles" Raspberry Pi Car - Fix and Get the Raspberry Pi IP Address

28 "Wanli" Raspberry Pi car - car assembly

29 "Wanli" Raspberry Pi car - straight-driving deviation problem and new control mode

30. "Wanli" Raspberry Pi car - Phase 1 completed demonstration (introduction from scratch)

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Summary (12 articles updated): lb8820265's "Wanli" Raspberry Pi car open source sharing

https://en.eeworld.com/bbs/thread-1187606-1-1.html