Keyboard Control

In this project, we will learn how to use the keyboard to remotely control the PiCrawler. You can control the PiCrawler to move forward, backward, left, and right.

Run the Code

cd /home/pi/picrawler/examples
sudo python3 keyboard_control.py

Code

from picrawler import Picrawler
from time import sleep
import sys
import tty
import termios



crawler = Picrawler([10,11,12,4,5,6,1,2,3,7,8,9])
#crawler.set_offset([0,0,0,0,0,0,0,0,0,0,0,0])
speed = 90

def readchar():
    fd = sys.stdin.fileno()
    old_settings = termios.tcgetattr(fd)
    try:
        tty.setraw(sys.stdin.fileno())
        ch = sys.stdin.read(1)
    finally:
        termios.tcsetattr(fd, termios.TCSADRAIN, old_settings)
    return ch


manual = '''
Press keys on keyboard to control PiSloth!
    W: Forward
    A: Turn left
    S: Backward
    D: Turn right
'''

def main():

    print(manual)

    while True:
        key = readchar()
        print(key)
        if 'w' == key:
            crawler.do_action('forward',1,speed)
        elif 's' == key:
            crawler.do_action('backward',1,speed)
        elif 'a' == key:
            crawler.do_action('turn left',1,speed)
        elif 'd' == key:
            crawler.do_action('turn right',1,speed)
        elif chr(27) == key:# 27 for ESC
            break

        sleep(0.05)
    print("\n q Quit")


if __name__ == "__main__":
    main()

How it works?

This function refers to the standard input stream and returns the first character of the data stream read.

• tty.setraw(sys.stdin.fileno) is to change the standard input stream to raw mode, that is, all characters will not be escaped during transmission, including special characters. Before changing the mode, back up the original mode, and restore it after the change.

• old_settings = termios.tcgetattr(fd) and termios.tcsetattr(fd, termios.TCSADRAIN, old_settings) plays the role of backup and restore.

def readchar():
            fd = sys.stdin.fileno()
            old_settings = termios.tcgetattr(fd)
            try:
                    tty.setraw(sys.stdin.fileno())
                    ch = sys.stdin.read(1)
            finally:
                    termios.tcsetattr(fd, termios.TCSADRAIN, old_settings)
            return ch

Finally, according to the read keyboard characters, let PiCrawler do the actions we set.

key = readchar()
print(key)
if 'w' == key:
    crawler.do_action('forward',1,speed)
elif 's' == key:
    crawler.do_action('backward',1,speed)
elif 'a' == key:
    crawler.do_action('turn left',1,speed)
elif 'd' == key:
    crawler.do_action('turn right',1,speed)
elif chr(27) == key:# 27 for ESC
    break