PWMOut on RPi Pico not able to run at full duty cycle

[jedgarpark]

I've run into an issue w PWMOut on RP2040 Pico board while using adafruit_motor. Seems that setting the PWM pins to full duty cycle of 0xFFFF fails to turn the motor, but 0xFFFE turns it just fine. This means the adafruit_motor throttle = 1.0 or throttle = -1.0 values don't work. I found that throttle = 0.9999998 works, but 0.9999999 does not.

I'm using GP28 and GP27 on the Pico.

Running adafruit-circuitpython-raspberry_pi_pico-en_US-20210212-08f30fe.uf2
Library from this bundle adafruit-circuitpython-bundle-6.x-mpy-20210212

here's the code I'm running:

# This example uses an L9110 H-bridge driver to run a DC Motor.
#  https://www.adafruit.com/product/4489

# Hardware setup:
#   DC motor via L9110 H-bridge driver on two PWM pins that are on their own channels
#   e.g., RP2040 Pico pins GP28, GP27

import time
import board
import pwmio
from adafruit_motor import motor

PWM_PIN_A = board.GP28  # pick any pwm pins on their own channels
PWM_PIN_B = board.GP27

# DC motor setup
pwm_a = pwmio.PWMOut(PWM_PIN_A, frequency=50)
pwm_b = pwmio.PWMOut(PWM_PIN_B, frequency=50)
motor1 = motor.DCMotor(pwm_a, pwm_b)


print("Forwards slow")
motor1.throttle = 0.5
print("throttle:", motor1.throttle)
print(hex(pwm_a.duty_cycle), hex(pwm_b.duty_cycle)+"\n")
time.sleep(1)

print("Stop")
motor1.throttle = 0
print("throttle:", motor1.throttle)
print(hex(pwm_a.duty_cycle), hex(pwm_b.duty_cycle)+"\n")
time.sleep(1)

print("Forwards")
motor1.throttle = 1.0  # 0.9999998 works, 0.9999999 does not
print("throttle:", motor1.throttle)
print(hex(pwm_a.duty_cycle), hex(pwm_b.duty_cycle)+"\n")
time.sleep(1)

print("Stop")
motor1.throttle = 0
print("throttle:", motor1.throttle)
print(hex(pwm_a.duty_cycle), hex(pwm_b.duty_cycle)+"\n")
time.sleep(1)

print("Backwards")
motor1.throttle = -1.0
print("throttle:", motor1.throttle)
print(hex(pwm_a.duty_cycle), hex(pwm_b.duty_cycle)+"\n")
time.sleep(1)

print("Stop")
motor1.throttle = 0
print("throttle:", motor1.throttle)
print(hex(pwm_a.duty_cycle), hex(pwm_b.duty_cycle)+"\n")
time.sleep(1)

print("Backwards slow")
motor1.throttle = -0.5
print("throttle:", motor1.throttle)
print(hex(pwm_a.duty_cycle), hex(pwm_b.duty_cycle)+"\n")
time.sleep(1)

print("Stop")
motor1.throttle = 0
print("throttle:", motor1.throttle)
print(hex(pwm_a.duty_cycle), hex(pwm_b.duty_cycle)+"\n")
time.sleep(1)

print("Spin freely")
motor1.throttle = None
print("throttle:", motor1.throttle)
print(hex(pwm_a.duty_cycle), hex(pwm_b.duty_cycle)+"\n")

print('pwmio test 0XFFFF \n')
pwm_a.duty_cycle = 0xFFFF
pwm_b.duty_cycle = 0x0000
time.sleep(4)

print('pwmio test 0XFFFE \n')
pwm_a.duty_cycle = 0xFFFE
pwm_b.duty_cycle = 0x0000
time.sleep(4)