"""
CLI Meter
== == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == ==
Takes a reading of the light using the meter attached via to the
intended Raspberry PI . The reading is the sent to a server where the
reading is stored . The intended use for this script is to be run via
the command - line without the need for a G . U . I . This should be the
version used when the " Return to Ritherdon " project is live .
"""
import json
import RPi . GPIO as GPIO
import time , math
import requests
from datetime import datetime
import pdb
# Using BCM (Broadcom) names when referencing the GPIO pins.
GPIO . setmode ( GPIO . BCM )
GPIO . setwarnings ( True )
a_pin = 18 # Charges the capacitor.
b_pin = 23 # Discharges the capacitor.
api_url = " http://35.176.14.135/api/readings/add/1 "
def discharge ( ) :
GPIO . setup ( a_pin , GPIO . IN )
GPIO . setup ( b_pin , GPIO . OUT )
GPIO . output ( b_pin , False )
time . sleep ( 0.01 ) # 0.01 -- initial value
def charge_time ( ) :
GPIO . setup ( b_pin , GPIO . IN )
GPIO . setup ( a_pin , GPIO . OUT )
GPIO . output ( a_pin , True )
t1 = time . time ( )
while not GPIO . input ( b_pin ) :
pass
t2 = time . time ( )
return ( t2 - t1 ) * 1000000
def analog_read ( ) :
discharge ( )
return charge_time ( )
def read_resistance ( ) :
n = 20
total = 0 ;
for i in range ( 1 , n ) :
total = total + analog_read ( )
reading = total / float ( n )
resistance = reading * 6.05 - 939
return resistance
def light_from_r ( R ) :
return math . log ( 1000000.0 / R ) * 10.0
def get_timestamp ( ) :
return datetime . now ( ) . strftime ( ( " % Y- % m- %d % H: % M: % S " ) )
def push_reading ( lvalue ) :
time = get_timestamp ( )
headers = { " content-type " : " application/json " }
payload = { " reading " : int ( lvalue ) , " time " : time }
print ( payload )
res = requests . post ( api_url , data = json . dumps ( payload ) , headers = headers )
def update_reading ( ) :
light = light_from_r ( read_resistance ( ) )
reading_str = " {:.0f} " . format ( light )
print ( reading_str )
push_reading ( light )
def main ( ) :
try :
while True :
#pdb.set_trace()
update_reading ( )
except KeyboardInterrupt :
print ( " Keyboard Interrupt: quitting program. " )
except :
print ( " Error updating light reading... " )
finally :
print ( " Cleaning up GPIO before closing... " )
GPIO . cleanup ( )
if __name__ == " __main__ " :
main ( )