barebones.py

# Headless Bare-Bones version of sploosh. No screen, no dials, uses battery
# List of pins
#
# ADC: 26 (for moisuture reading)
# Relaypin: 15
# LED: 25 (onboard)
 
from machine import Pin,I2C,ADC
import utime
import gc

# The Tweakable values that will help tune for our use case
calibratewet=20000 # ADC value for a very wet thing
calibratedry=50000 # ADC value for a very dry thing
checkin = 5 # Time interval (seconds) for each cycle of monitoring loop
# PID Parameters
# Description Stolen From Reddit: In terms of steering a ship:
# Kp is steering harder the further off course you are,
# Ki is steering into the wind to targetact a drift
# Kd is slowing the turn as you approach your course
Kp=2   # Proportional term - Basic steering (This is the first parameter you should tune for a particular setup)
Ki=0   # Integral term - Compensate for heat loss by vessel
Kd=0  # Derivative term - to prevent overshoot due to inertia - if it is zooming towards setpoint this
      # will cancel out the proportional term due to the large negative gradient
target=6 # Target Wetness For Plant

# Initialise Pins
led=Pin(25,Pin.OUT) # Blink onboard LED as proof-of-life
relaypin = Pin(15, mode = Pin.OUT)
wetness = machine.ADC(26)
# Blink LED as proof of life
led.value(1) 
utime.sleep(.2) 
led.value(0)
# Initialise 
gc.enable() # Garbage collection enabled
integral = 0
lastupdate = utime.time()  
lasterror = 0
output=0
offstate=True
# PID infinite loop 
while True:
    try:
        # Get wetness
        imwet=wetness.read_u16()
        howdry = min(10,max(0,10*(imwet-calibratedry)/(calibratewet-calibratedry))) # linear relationship between ADC and wetness, clamped between 0, 10
        now = utime.time()
        dt= now-lastupdate
        if  offstate == False and dt > checkin * round(output)/100 :
            relaypin = Pin(15, mode = Pin.OUT, value =0 )
            offstate= True
            utime.sleep(.1)
        if dt > checkin:
            print("WETNESS",howdry)
            error=target-howdry
            integral = integral + dt * error
            derivative = (error - lasterror)/dt
            output = Kp * error + Ki * integral + Kd * derivative
            print(str(output)+"= Kp term: "+str(Kp*error)+" + Ki term:" + str(Ki*integral) + "+ Kd term: " + str(Kd*derivative))
            output = max(min(100, output), 0) # Clamp output between 0 and 100
            print("OUTPUT ",output)
            if output>0:  
                relaypin.value(1)
                offstate = False
            else:
                relaypin.value(0)
                offstate = True
            utime.sleep(.1)
            lastupdate = now
            lasterror = error  
    except Exception as e:
        print('error encountered:'+str(e))
        utime.sleep(checkin)