Remove ENA jumpers for PWM
Uno PWM pins are 3, 5, 6, 9, 10, 11. 8-bit PWM output with analogWrite().
Example PWM frequency -- 200 Hz.
0 0 Brake
0 1 Backward
1 0 Forward
1 1 Brake
Pulse width on ENA pin
analogWrite(pin, 255); /* 100% duty cycle */
analogWrite(pin, 127); /* 50% duty cycle */
Arduino PWM frequency 490 to 980 Hz
You do not need to call pinMode() to set the pin as an output before calling analogWrite().
pinMode(pin, OUTPUT);
digitalWrite(pin, HIGH);
digitalWrite(pin, LOW);
delay(1000);