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#!/usr/bin/env python2.7
# script by Alex Eames http://RasPi.tv
# explained here...
# http://raspi.tv/2013/controlled-shutdown-duration-test-of-pi-model-a-with-2-cell-lipo
# DO NOT use this script without a Voltage divider or other means of
# reducing battery voltage to the ADC. This is exaplained on the above blog page
import time
import os
import subprocess
import smtplib
import string
import RPi.GPIO as GPIO
from time import gmtime, strftime
GPIO.setmode(GPIO.BCM)
################################################################################
######################### Program Variables you MUST SET #######################
# email variables
fromaddr = 'your_gmail_account@gmail.com'
toaddr = 'destination email address'
# Googlemail login details
username = 'your googlemail/gmail username'
password = 'your googlemail/gmail password'
########## Program variables you might want to tweak ###########################
# voltage divider connected to channel 0 of mcp3002
adcs = [0] # 0 battery voltage divider
reps = 10 # how many times to take each measurement for averaging
cutoff = 7.5 # cutoff voltage for the battery
previous_voltage = cutoff + 1 # initial value
time_between_readings = 60 # seconds between clusters of readings
# Define Pins/Ports
SPICLK = 8 # FOUR SPI ports on the ADC
SPIMISO = 23
SPIMOSI = 24
SPICS = 25
####### You shouldn't need to change anything below here #######################
################################################################################
# read SPI data from MCP3002 chip, 2 possible adc's (0 & 1)
# this uses a bitbang method rather than Pi hardware spi
# modified code based on an adafruit example for mcp3008
def readadc(adcnum, clockpin, mosipin, misopin, cspin):
if ((adcnum > 1) or (adcnum < 0)):
return -1
if (adcnum == 0):
commandout = 0x6
else:
commandout = 0x7
GPIO.output(cspin, True)
GPIO.output(clockpin, False) # start clock low
GPIO.output(cspin, False) # bring CS low
commandout <<= 5 # we only need to send 3 bits here
for i in range(3):
if (commandout & 0x80):
GPIO.output(mosipin, True)
else:
GPIO.output(mosipin, False)
commandout <<= 1
GPIO.output(clockpin, True)
GPIO.output(clockpin, False)
adcout = 0
# read in one empty bit, one null bit and 10 ADC bits
for i in range(12):
GPIO.output(clockpin, True)
GPIO.output(clockpin, False)
adcout <<= 1
if (GPIO.input(misopin)):
adcout |= 0x1
GPIO.output(cspin, True)
adcout /= 2 # first bit is 'null' so drop it
return adcout
# this function creates and logs to a file called battery_log.txt
# you can change the name if you want, but you'll have to change line 98 as well
def write_log(logline):
logfile = open('battery_log.txt', 'a')
logfile.write(logline + '\n')
logfile.close()
# you can edit the text for the email to suit your requirements
def send_email():
BODY = string.join((
"From: %s" % fromaddr,
"To: %s" % toaddr,
"Subject: Shutting down the model A now",
"",
"Your battery voltage was just measured at or below threshold.",
"If it happens twice in a row, we shut down.",
), "\r\n")
# send the email
server = smtplib.SMTP('smtp.gmail.com:587')
server.starttls()
server.login(username,password)
server.sendmail(fromaddr, toaddr, BODY)
server.quit()
#Set up ports
GPIO.setup(SPIMOSI, GPIO.OUT) # set up the SPI interface pins
GPIO.setup(SPIMISO, GPIO.IN)
GPIO.setup(SPICLK, GPIO.OUT)
GPIO.setup(SPICS, GPIO.OUT)
# create log file
item = 'Battery log data'
logfile = open('battery_log.txt', 'w')
logfile.write(item + '\n')
logfile.close()
try:
while True:
for adcnum in adcs:
# read the analog pin
adctot = 0
for i in range(reps):
read_adc = readadc(adcnum, SPICLK, SPIMOSI, SPIMISO, SPICS)
adctot += read_adc
time.sleep(0.05)
read_adc = adctot / reps / 1.0
print read_adc
# convert analog reading to Volts = ADC * ( 3.33 / 1024 )
# 3.33 tweak according to the 3v3 measurement on the Pi
volts = read_adc * ( 3.33 / 1024.0) * 2.837
voltstring = str(volts)[0:5]
print "Battery Voltage: %.2f" % volts
# now we need to log the time and voltage in the log file
logline = str(strftime("%Y-%m-%d %H:%M:%S", gmtime()))
logline += ', '
logline += voltstring
print "adding %s to log file" % logline
write_log(logline)
# put safeguards in here so that it takes 2 or 3 successive readings
if volts <= cutoff:
# get it to send you an email at this point before full cutoff
try:
send_email()
print "email sent"
except:
print "email failed"
if previous_voltage <= cutoff:
logline = 'Shutting down due to low V at '
logline += str(strftime("%Y-%m-%d %H:%M:%S", gmtime()))
write_log(logline)
# initiate shutdown process
print "OK. Syncing file system, then we're shutting down."
command = os.system("sync")
command = 0
if command == 0:
print "we're shutting down now"
command = "/usr/bin/sudo /sbin/shutdown -h now"
process = subprocess.Popen(command.split(), stdout=subprocess.PIPE)
output = process.communicate()[0]
print output
previous_voltage = volts
time.sleep(time_between_readings)
except KeyboardInterrupt: # trap a CTRL+C keyboard interrupt
GPIO.cleanup()
time.sleep(5)
GPIO.cleanup()
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