Reduce Sensor Messaging Noise to MQTT

Question

I'm running MicroPython on an ESP32 relaying sensor data to my MQTT server for Home Assistant. I only want it to emit a message when state has changed and a motion detected state to hold for a minute before returning to a clear state. I see a lot of examples using sleep, but I don't like the blocking nature of sleep as I will be adding more sensors. Instead I've been using ticks_ms() and ticks_diff() to keep the state from fluttering on/off too much, but I can't help but think there's a better/more elegant way to do this that I'm not seeing.

There's some repetition and nesting that sticks out to me

from umqtt.robust import MQTTClient
from machine import Pin, unique_id
from time import ticks_diff, ticks_ms
from ubinascii import hexlify
#Config
MQTT_SERVER = "X.X.X.X"
MQTT_PORT = 1883
MQTT_USER = b"USER"
MQTT_PASSWORD = b"PASSWORD"
MQTT_CLIENT_ID = hexlify(unique_id())
MQTT_TOPIC = b"esp/motion"
mqtt = MQTTClient(MQTT_CLIENT_ID, MQTT_SERVER, MQTT_PORT, MQTT_USER, MQTT_PASSWORD)
ledPin = Pin(2, Pin.OUT)
motPin = Pin(15, Pin.IN)
previousState = 0
delay_ms = 60000
clock = ticks_ms()
def main():
 global clock, previousState, delay_ms
 try:
 mqtt.connect()
 while True:
 state = motPin.value()
 if state == 1:
 ledPin.on()
 if previousState == 0:
 if ticks_diff(ticks_ms(), clock) >= 0:
 print('motion_start')
 mqtt.publish(MQTT_TOPIC, 'motion_start')
 clock = ticks_ms() + delay_ms
 previousState = state
 else:
 clock = ticks_ms() + delay_ms
 else:
 ledPin.off()
 if previousState == 1:
 if ticks_diff(ticks_ms(), clock) >= 0:
 print('motion_stop')
 mqtt.publish(MQTT_TOPIC, 'motion_stop')
 previousState = state
 finally:
 ledPin.off()
 mqtt.publish(MQTT_TOPIC, 'motion_stop')
 mqtt.disconnect()
if __name__ == "__main__":
 main()

Answer 1

Fluttering

 if previousState == 0:
 if ticks_diff(ticks_ms(), clock) >= 0:

This is called a soft debounce. It may or may not be adequate. My usual recommendation is to do hard debounce instead (or maybe in addition) via a first-order RC lowpass filter followed by hysteresis in a Schmitt trigger. If none of that makes sense to you, then that's a question for https://electronics.stackexchange.com/ .

Truthiness

I would sooner write

if state:

rather than

if state == 1:

snake_case

Per PEP8, previousState should be previous_state.

• weird.turned.pro: What I'm aiming for isn't necessarily debouncing as the sensor has digital signal processing; multiple motion events all within a minute just tend to present issues with home automation. Agreed on the state boolean - I had that initially, but thought that might obfuscate sensor value too much - but it is indeed cleaner.