Store and read light sensor values with Spike Prime - system.storage

[Aldeatron]

Hi everyone!

We try to store the B&W light intensity values and read later in a line follower code with "system.storage". We don´t quite understand how to store and read binary data and then convert it to a number we could use as light intensity. Can anyone explain how it can be done and give an example if possible?

Thank you!

[laurensvalk]

For small numbers (between 0 and 255), not much conversion is required. Here is an example:

from pybricks.hubs import PrimeHub

hub = PrimeHub()

# In this example we alway store it at the start of the memory.
START = 0

# Each number may be between 0 and 255
write_values = [7, 8, 9, 35, 200]
print("I store", write_values)
hub.system.storage(START, write=bytes(write_values))

# You can read it now. Even if you delete the values above
# the second time. Even after restart.
read_values = [v for v in  hub.system.storage(START, read=5)]
print("I read ", read_values)

[Aldeatron]

Thank you very much!

[Aldeatron]

Hi! How could we store and read float numbers?

[Aldeatron]

Thanks!

[Aldeatron]

Hi again! Sorry about so many questions.

This is the way we store our 4 float values:

We have tried this so far to unpack them:

But when we print them we obtain the integer values stored in previous tests, not the float ones.

Thank you!

[laurensvalk]

I don't seem to see a write command anywhere, e.g.:

hub.system.storage(START, write=bytes(write_values))

That said, if you are essentially storing information about light sensor values (which can only measure from 0--100), I'll probably still recommend just storing those :)

[Aldeatron]

Thank you!

We also need to store correction factors (CorrecE & CorrecF), which are float numbers.

[dlech]

FYI, you can encode more types (int, str) using ustruct.pack(). See the table at the bottom of https://docs.pybricks.com/en/stable/micropython/ustruct.html.