How to do a simple subtraction

[hanslammerts]

I'm sorry.
Just started out with micropython (for the Py Pico) and one of the simplest things fail.
Please have a look at the following snippet:

`
from machine import Pin

import utime

def heartbeat(currentms):
setup = False
print(currentms)

def loop():

loopTimer = utime.ticks_ms
maxLoopTime = 0
maxLoopTime = max(maxLoopTime, (utime.ticks_ms - loopTimer))
loopTimer = utime.ticks_ms

currentMillis = utime.ticks_ms
heartbeat(currentMillis)

if __name__ == '__main__':
loop()
`

The error I get:

Operator "-" not supported for types "() -> int" and "() -> int"

How do I subtract loopTimer from utime.ticks_ms ?
Also, the code backticks don't seem to work....
Indentation disappears....
Thanks.

[dhalbert]

Use utime.ticks_ms(), with parentheses. You have to call it as a function: it's not a property. Also note now time instead of utime is preferred.

[scruss]

Also, you can't reliably use simple subtraction on ticks counters. These roll over at around 2**30. Use the time.ticks_diff(ticks1, ticks2) function instead.

Here's what I think your code should look like:

from machine import Pin
import time


def heartbeat(currentms):
    setup = False
    print(currentms)


def loop():
    loopTimer = time.ticks_ms
    maxLoopTime = 0
    maxLoopTime = max(
        maxLoopTime, (time.ticks_diff(time.ticks_ms(), loopTimer))
    )
    loopTimer = time.ticks_ms()
    currentMillis = time.ticks_ms()
    heartbeat(currentMillis)


if __name__ == "__main__":
    loop()

(though impossible to tell since indentation was lost. Please read the Welcome (Please read before posting) entry on how to post code so it's readable.)