Camera() instantiation breaks stable usage of UltrasonicSensor()

[duwudi]

from pitop import (
    Camera,
    UltrasonicSensor,
)
from time import sleep

camera = Camera(resolution=(640, 480))

ultrasonic = UltrasonicSensor("D3")

while True:
    print(f"Distance: {ultrasonic.distance}")
    sleep(0.1)

If the camera instantiation is commented out, the program runs normally and distance readings make sense.

With the camera, the following problems occur:

• The first call to ultrasonic.distance hangs for 8-10 seconds. This hanging also happens sporadically throughout subsequent calls too.
• The readings returned are unstable and do not represent the actual distance at all. For example, the distance returned with the hand at around 0.1m away from the sensor is 0.6m - the returned readings seem to span 0.6-1.0m regardless of the true distance.

Pin Factory Test: Problem occurs whether using the default pin factory or if using NativeFactory() as we did previously - so I don't think this is caused by a382aa5

htop screenshot whilst program running:

[duwudi]

Note: workaround for this is #368 - we should encourage using A1 and A3 for the ultrasonic sensor as it isn't susceptible to timing issues that are prevalent on the Raspberry Pi