Memory allocation error when multitasking

[pcakl]

I have a program for a train that has 2 main functions:
1 is to get the data from multiple hubs via bluetooth and see availability of the train tracks.
2 is to read the color sensor to see if there is any action color on the track.

In order to work this properly I need to read from sensor roughly every 20ms but the 1 function (data gathering via bluetooth) takes to run roughly 100ms.

For this reason I tried to use multitasking to run the train independently from the data gathering. However while trying to multitask I am getting memory allocation error even when I stripped code to minimum just to test it out after couple of runs.

My question is then - am I trying to multitask incorrectly or do I need to do some manual memory cleanup each run ?

When I try to run program without multitasking it runs just fine the only problem is that train is not able to pick up the action colors because the whole routine takes too long (due to data processing via bluetooth observing). When I try to print out memory allocation there it is showing that free memory is decreasing each run but then it is freed up somehow when it is too low and I never get the allocation error.

This is the simplified code:

# Initialize hub
observe_channels = get_observe_channels(track_configs)
hub = CityHub(observe_channels=observe_channels)

train_motor = DCMotor(Port.A, Direction.CLOCKWISE)
train_sensor = ColorDistanceSensor(Port.B)

# Only see defined colours
train_sensor.detectable_colors(sensor_colors)

track_available = 0
counter = 1

async def get_data():
    global track_available
    
    while True:
        if track_available == 0:
            track_available = 1
        
        elif track_available == 1:
            track_available = 0

        await wait(100)

async def do_loop():
    while True:
        global counter

        actual_color = train_sensor.color()
        print(counter)
        counter += 1
        print('Track available: ' + str(track_available))
        mem_info()
        await wait(20)

async def main():
    await multitask(get_data(),do_loop())

run_task(main())

This is the output (removed the first initial 53 runs that run fine):

54
Track available: 0
stack: 1244 out of 5180
GC: total: 15296, used: 15104, free: 192
 No. of 1-blocks: 463, 2-blocks: 125, max blk sz: 32, max free sz: 12
55
Track available: 1
stack: 1244 out of 5180
GC: total: 15296, used: 15216, free: 80
 No. of 1-blocks: 466, 2-blocks: 127, max blk sz: 32, max free sz: 5
56
Track available: 0
stack: 1244 out of 5180
GC: total: 15296, used: 9616, free: 5680
 No. of 1-blocks: 232, 2-blocks: 69, max blk sz: 32, max free sz: 32
57
Track available: 0
stack: 1244 out of 5180
GC: total: 15296, used: 9728, free: 5568
 No. of 1-blocks: 235, 2-blocks: 71, max blk sz: 32, max free sz: 32
58
Track available: 1
stack: 1244 out of 5180
GC: total: 15296, used: 9840, free: 5456
 No. of 1-blocks: 238, 2-blocks: 73, max blk sz: 32, max free sz: 32
59
Track available: 0
stack: 1244 out of 5180
GC: total: 15296, used: 9952, free: 5344
 No. of 1-blocks: 241, 2-blocks: 75, max blk sz: 32, max free sz: 32
60
Track available: 0
stack: 1244 out of 5180
GC: total: 15296, used: 10064, free: 5232
 No. of 1-blocks: 244, 2-blocks: 77, max blk sz: 32, max free sz: 32
61
Track available: 1
stack: 1244 out of 5180
GC: total: 15296, used: 10176, free: 5120
 No. of 1-blocks: 247, 2-blocks: 79, max blk sz: 32, max free sz: 32
62
Track available: 1
stack: 1244 out of 5180
GC: total: 15296, used: 10288, free: 5008
 No. of 1-blocks: 250, 2-blocks: 81, max blk sz: 32, max free sz: 25
63
Track available: 0
stack: 1244 out of 5180
GC: total: 15296, used: 10400, free: 4896
 No. of 1-blocks: 253, 2-blocks: 83, max blk sz: 32, max free sz: 18
64
Track available: 0
stack: 1244 out of 5180
GC: total: 15296, used: 10512, free: 4784
 No. of 1-blocks: 256, 2-blocks: 85, max blk sz: 32, max free sz: 14
Traceback (most recent call last):
  File "test_multitask.py", line 133, in <module>
  File "test_multitask.py", line 131, in main
  File "test_multitask.py", line 119, in do_loop
MemoryError: memory allocation failed, allocating 512 bytes

It is failing on the line when I try to read from the color sensor - actual_color = train_sensor.color().

[pcakl]

Seems like putting await in front of train_sensor.color() fixed it :-)

actual_color = await train_sensor.color()