PymateIO-Delaying

Abstract

The "Cycle Timing" tutorial state the following:

NEVER USE BLOCKING INSTRUCTION in the mainloop

Blocking instruction locks the script execution in a waiting state... whereas critical operation may requires quick reaction from the script.

The sleep(), sleep_ms() are BLOCKING INSTRUCTIONS.
They should never be used in your script, neither in the mainloop

The solution for this is:

• use the EventTimer class
• set the delay on the EventTimer when the source event occurs.
• check the EventTimer.done at every mainloop cycle.
• Once done, it is time to executed the delayed code.

Remark: the done will assert True only once for every set()!

Practical example

As practical example, we will read DS18B20 OneWire sensor connected on the Pymate Expansion port.

The problem with the DS18B20 is required pause of 750ms between the temperature request and values reading.

Wiring DS18B20

Blocking script

Here follow a basic MicroPython script showing how to deal with the DS18B20 sensor.

This script makes a reading every 5 seconds (execution limited to 10 iteration).

Unfortunately, this use blocking instructions like sleep_ms() and sleep().

from machine import Pin
import onewire, ds18x20
import time

dat = Pin( "I2C4_SMB", Pin.IN )
bus = onewire.OneWire(dat)
ds  = ds18x20.DS18X20( bus )

roms = ds.scan()
print( "Found devices", roms )

for i in range(10):
	print( "%i: Read temperature" %i )
	ds.convert_temp()
	time.sleep_ms(750) # Required by OneWire protocol
	for rom in roms:
		print( 'ROM', rom, 'Temperature', ds.read_temp(rom) )
	time.sleep( 5 )

print( "That's all Folks" )

Which produce the following:

Found devices [bytearray(b'(\xf2\t\x94\x97\x03\x03\xfb')]
0: Read temperature
ROM bytearray(b'(\xf2\t\x94\x97\x03\x03\xfb') Temperature 20.5625
1: Read temperature
ROM bytearray(b'(\xf2\t\x94\x97\x03\x03\xfb') Temperature 20.5
2: Read temperature
ROM bytearray(b'(\xf2\t\x94\x97\x03\x03\xfb') Temperature 20.5
3: Read temperature
ROM bytearray(b'(\xf2\t\x94\x97\x03\x03\xfb') Temperature 20.5
4: Read temperature
ROM bytearray(b'(\xf2\t\x94\x97\x03\x03\xfb') Temperature 20.5625
5: Read temperature
ROM bytearray(b'(\xf2\t\x94\x97\x03\x03\xfb') Temperature 20.5
6: Read temperature
ROM bytearray(b'(\xf2\t\x94\x97\x03\x03\xfb') Temperature 20.5
7: Read temperature
ROM bytearray(b'(\xf2\t\x94\x97\x03\x03\xfb') Temperature 20.5
8: Read temperature
ROM bytearray(b'(\xf2\t\x94\x97\x03\x03\xfb') Temperature 20.5
9: Read temperature
ROM bytearray(b'(\xf2\t\x94\x97\x03\x03\xfb') Temperature 20.5
That's all Folks

Pymate Non-Blocking script

This implementation do use the EventTimer class to create non-blocking delay.

Once the EventTimer.set() called, the property done will the True only when the time is elapsed.

Notes that done will be True only once for each EventTimer.set().

from machine import Pin
from pymate import EventTimer
import onewire, ds18x20
import time

dat = Pin( "I2C4_SMB", Pin.IN )
bus = onewire.OneWire(dat)
ds  = ds18x20.DS18X20( bus )
roms = ds.scan()
first_rom = roms[0] # Only remember first rom 
print( "Found device", first_rom )

i = 0
convert_event = EventTimer(0.1) # Immediately starts
read_event = EventTimer() # Do not start this one
while True:
	if convert_event.done:
		ds.convert_temp()
		read_event.set(0.750)  # Prepare the reading in 750 ms
		convert_event.set( 5 ) # Prepare for next conversion request

	if read_event.done:
		print( 'ROM', first_rom, 'Temperature', ds.read_temp(first_rom) )
		print( 'i', i )
	
	# Remain of code to execute
	i += 1

The mainloop can run full speed as demonstrates the i variable that get incremented at each mainloop pass.

The incrementation of i shows the effectiveness of non-blocking delay for convert_temp() and read_temp() .

Found devices bytearray(b'(\xf2\t\x94\x97\x03\x03\xfb')
ROM bytearray(b'(\xf2\t\x94\x97\x03\x03\xfb') Temperature 20.625
i 0
ROM bytearray(b'(\xf2\t\x94\x97\x03\x03\xfb') Temperature 20.375
i 6583
ROM bytearray(b'(\xf2\t\x94\x97\x03\x03\xfb') Temperature 20.4375
i 58218
ROM bytearray(b'(\xf2\t\x94\x97\x03\x03\xfb') Temperature 20.5
i 109931
ROM bytearray(b'(\xf2\t\x94\x97\x03\x03\xfb') Temperature 20.4375
i 161604
ROM bytearray(b'(\xf2\t\x94\x97\x03\x03\xfb') Temperature 20.375
i 213262

---

PymateIO all right reserved © 2026 - Written by MCHobby for PymateIO