2 motors on L298N controlled with GPIO from Rpi3B .. python telling me channel already in use and motors not turning

Question

I have adopted Electronics hub tutorial to run 2 motors from a L298N controlled by Rpi3B using GPIO.

Why is my version of the code not working?

I do understand that I could ignore the "channel already in use" warning but I thought I would mention in case they really are being used elsewhere. The code is below. A pic attached is showing the warnings and the results of "raspi-gpio get". Also included is a very rough and ready wiring diagram and io table between Rpi3B & L298N MC.

import RPi.GPIO as GPIO          
from time import sleep

# LHS enable
enA=12
# L_FWD
in1=23
# L_REV
in2=24
# RHS enable
enB=13
# R_FWD
in3=17
# R_REV
in4=27
temp1=1

GPIO.setmode(GPIO.BCM) # Broadcom pin-numbering scheme
GPIO.setup(enA,GPIO.OUT)
GPIO.setup(in1,GPIO.OUT)
GPIO.setup(in2,GPIO.OUT)
GPIO.setup(enB,GPIO.OUT)
GPIO.setup(in3,GPIO.OUT)
GPIO.setup(in4,GPIO.OUT)

p1=GPIO.PWM(enA,1000)
p2=GPIO.PWM(enB,1000)

p1.start(25)
p2.start(25)

print("\n")
print("The default speed & direction of motor is LOW & Forward.....")
print("r-run s-stop f-forward b-backward l-low m-medium h-high e-exit")
print("\n")    

while(1):

        x=input()
    
if x=='r':
        print("run")
if(temp1==1):

        GPIO.output(enA,GPIO.HIGH)
        GPIO.output(in1,GPIO.HIGH)
        GPIO.output(in2,GPIO.LOW)
        GPIO.output(enB,GPIO.HIGH)
        GPIO.output(in3,GPIO.HIGH)
        GPIO.output(in4,GPIO.LOW)
        print("forward")
        x='z'
        
elif x=='s':
        print("stop")
        GPIO.output(enA,GPIO.LOW)
        GPIO.output(in1,GPIO.LOW)
        GPIO.output(in2,GPIO.LOW)
        GPIO.output(enB,GPIO.LOW)
        GPIO.output(in3,GPIO.LOW)
        GPIO.output(in4,GPIO.LOW)
        x='z'

elif x=='f':
        print("forward")
        GPIO.output(enA,GPIO.HIGH)
        GPIO.output(in1,GPIO.HIGH)
        GPIO.output(in2,GPIO.LOW)
        GPIO.output(enB,GPIO.HIGH)
        GPIO.output(in3,GPIO.HIGH)
        GPIO.output(in4,GPIO.LOW)
        temp1=1
        x='z'
        
elif x=='b':
        print("backward")
        GPIO.output(enA,GPIO.HIGH)
        GPIO.output(in1,GPIO.LOW)
        GPIO.output(in2,GPIO.HIGH)
        GPIO.output(enB,GPIO.HIGH)
        GPIO.output(in3,GPIO.LOW)
        GPIO.output(in4,GPIO.HIGH)
        temp1=0
        x='z'

elif x=='l':
        print("low")
        p1.ChangeDutyCycle(25)
        p2.ChangeDutyCycle(25)
        x='z'

elif x=='m':
        print("medium")
        p1.ChangeDutyCycle(50)
        p2.ChangeDutyCycle(50)
        x='z'

elif x=='h':
        print("high")
        p1.ChangeDutyCycle(75)
        p2.ChangeDutyCycle(75)
        x='z'
     
elif x=='e':
        GPIO.cleanup()
        print("GPIO Clean up")
        
else:
        print("<<<  wrong data  >>>")
        print("please enter the defined data to continue.....")

here is the GPIO Get response

pi@RozPi:~ $ raspi-gpio get BANK0 (GPIO 0 to 27):

GPIO 0: level=1 fsel=0 func=INPUT

GPIO 1: level=1 fsel=0 func=INPUT

GPIO 2: level=1 fsel=4 alt=0 func=SDA1

GPIO 3: level=1 fsel=4 alt=0 func=SCL1

GPIO 4: level=1 fsel=0 func=INPUT

GPIO 5: level=1 fsel=0 func=INPUT

GPIO 6: level=1 fsel=0 func=INPUT

GPIO 7: level=1 fsel=1 func=OUTPUT

GPIO 8: level=1 fsel=1 func=OUTPUT

GPIO 9: level=0 fsel=4 alt=0 func=SPI0_MISO

GPIO 10: level=0 fsel=4 alt=0 func=SPI0_MOSI

GPIO 11: level=0 fsel=4 alt=0 func=SPI0_SCLK

GPIO 12: level=1 fsel=1 func=OUTPUT

GPIO 13: level=1 fsel=1 func=OUTPUT

GPIO 14: level=1 fsel=2 alt=5 func=TXD1

GPIO 15: level=1 fsel=2 alt=5 func=RXD1

GPIO 16: level=0 fsel=0 func=INPUT

GPIO 17: level=0 fsel=1 func=OUTPUT

GPIO 18: level=0 fsel=0 func=INPUT

GPIO 19: level=0 fsel=0 func=INPUT

GPIO 20: level=0 fsel=0 func=INPUT

GPIO 21: level=0 fsel=0 func=INPUT

GPIO 22: level=0 fsel=0 func=INPUT

GPIO 23: level=0 fsel=1 func=OUTPUT

GPIO 24: level=0 fsel=1 func=OUTPUT

GPIO 25: level=0 fsel=0 func=INPUT

GPIO 26: level=0 fsel=0 func=INPUT

GPIO 27: level=0 fsel=1 func=OUTPUT

here are the warnings corresponding to the GPIO setup calls in the code above /home/pi/L298N_Dual.py:22: RuntimeWarning: This channel is already in use, continuing anyway. Use GPIO.setwarnings(False) to disable warnings. GPIO.setup(enA,GPIO.OUT) /home/pi/L298N_Dual.py:23: RuntimeWarning: This channel is already in use, continuing anyway. Use GPIO.setwarnings(False) to disable warnings. GPIO.setup(in1,GPIO.OUT) /home/pi/L298N_Dual.py:24: RuntimeWarning: This channel is already in use, continuing anyway. Use GPIO.setwarnings(False) to disable warnings. GPIO.setup(in2,GPIO.OUT) /home/pi/L298N_Dual.py:25: RuntimeWarning: This channel is already in use, continuing anyway. Use GPIO.setwarnings(False) to disable warnings. GPIO.setup(enB,GPIO.OUT) /home/pi/L298N_Dual.py:26: RuntimeWarning: This channel is already in use, continuing anyway. Use GPIO.setwarnings(False) to disable warnings. GPIO.setup(in3,GPIO.OUT) /home/pi/L298N_Dual.py:27: RuntimeWarning: This channel is already in use, continuing anyway. Use GPIO.setwarnings(False) to disable warnings. GPIO.setup(in4,GPIO.OUT)

Answer 1

I believe your code is OK. The L298 was never intended to operate with a Pi, it is 5V logic, about 4.5V minimum. If this is wrong please post an annotated schematic and a link to the "Technical Information" on the L298 module. I cannot tell how it is wired but 4 batteries will give you a little over 6V but as the motors run that voltage will drop because of the battery resistance and partially discharged.

You may also damage your Pi, it is my understanding that it should only be connected to an external power supply rated at 5V/2.5 A DC. A higher amperage rating of the power supply will be fine.