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

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

 

We have previously introduced the PWM and external interrupt simulation timers of the wiringPi library. In fact, Python's GPIO library also has PWM and external interrupt functions. You can try using this method to simulate the timer.

As before, short the BCM pins 17 and 18, set the PWM frequency to 100Hz, set the pin external interrupt, and output the number of times and the time difference between the two interrupts in the interrupt function.

Code

import RPi.GPIO as GPIO
import time
import datetime
def my_callback1(channel):
global pre_time
global spin_count
now = time.time()
cha=now-pre_time
pre_time=now
spin_count += 1
print(spin_count,cha)
pre_time=0;
spin_count = 0
In = 17
Out= 18
GPIO.setmode(GPIO.BCM)
GPIO.setup(In, GPIO.IN, pull_up_down=GPIO.PUD_UP)
GPIO.setup(Out, GPIO.OUT)
p = GPIO.PWM(Out, 100)
p.start(1)
GPIO.add_event_detect(In, GPIO.RISING, callback=my_callback1)
while True:
time.sleep(1)

result

Almost every time the time difference is greater than 10ms, and the error is within about 4%. This result seems to be similar to the result of the C++ code, but it is very bad that it times out every time, which shows that under fast external interrupts, serious time lags will occur.

This shows that Python's real-time performance is indeed worse than C language.

question

Through my exploration, the real-time performance of the Raspberry Pi system is indeed not very good. Although it has a powerful CPU, its real-time performance is not as good as that of a low-end microcontroller. No wonder many Raspberry Pi cars use a stm32 chip as the chassis of the car. The Raspberry Pi communicates with the stm32 through the serial port, but this method is not what I want. I hope to use a single Raspberry Pi to complete the production of the car.

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