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pi_power_leds.py
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pi_power_leds.py
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#!/usr/bin/env python
# pi_power_led.py
# Copyright (c) 2016 Robert Jones, Craic Computing LLC
# Freely distributed under the terms of the MIT License
# Read the contents of /home/pi/.pi_power_status and light red and green leds accordingly
# The default configuration for the LEDs is Common Anode which works for most RGB LEDs
# LED modes
# green blinking - USB cable attached, charging battery
# green constant - on battery, >= 0.5 fraction of battery life
# red constant - on battery, < 0.20 fraction of battery life
# red blinking - on battery, < 0.15 fraction of battery life
# red blinking fast - on battery, < 0.10 fraction of battery life
# .pi_power file format:
# one line - <battery fraction 0.0-1.0>,<power source - usb or battery>
# for example:
#1.00,usb
#0.50,battery
# Define each LED mode - set the on/off times here (in seconds) - 0 means always on
def green_constant():
blink_time_on = 0
blink_time_off = 0
leds = ['green']
update_leds(leds, blink_time_on, blink_time_off)
def red_constant():
blink_time_on = 0
blink_time_off = 0
leds = ['red']
update_leds(leds, blink_time_on, blink_time_off)
def yellow_constant():
blink_time_on = 0
blink_time_off = 0
leds = ['red', 'green']
update_leds(leds, blink_time_on, blink_time_off)
def green_blink():
blink_time_on = 2.0
blink_time_off = 0.5
leds = ['green']
update_leds(leds, blink_time_on, blink_time_off)
def red_blink():
blink_time_on = 1.0
blink_time_off = 1.0
leds = ['red']
update_leds(leds, blink_time_on, blink_time_off)
def red_blink_fast():
blink_time_on = 0.5
blink_time_off = 0.5
leds = ['red']
update_leds(leds, blink_time_on, blink_time_off)
def update_leds(current_leds, time_on, time_off):
global led_pin
global led_states
global poll_interval
if time_off == 0:
# constant on
for i in range(len(current_leds)):
GPIO.output(led_pin[current_leds[i]], led_states['on'])
time.sleep(poll_interval)
else:
# blink
n_cycles = int(float(poll_interval) / float(time_on + time_off))
for i in range(n_cycles):
# led on, sleep, led off, sleep
for i in range(len(current_leds)):
GPIO.output(led_pin[current_leds[i]], led_states['on'])
time.sleep(time_on)
for i in range(len(current_leds)):
GPIO.output(led_pin[current_leds[i]], led_states['off'])
time.sleep(time_off)
# MAIN -------------------------------------------------
import time
import os
import RPi.GPIO as GPIO
GPIO.setmode(GPIO.BCM)
GPIO.setwarnings(False)
# If you are using a common Anode RGB LED use these - most RGB Leds are this type
led_states = {'off': GPIO.HIGH, 'on': GPIO.LOW}
# If you are using a common Cathode configuration use this instead
# led_states = {'off': GPIO.LOW, 'on': GPIO.HIGH}
# Specify the RasPi GPIO pins to use - modufy these to suit your configuration
led_pin = {'red': 21, 'green': 20}
# check the pi_power file every poll_interval seconds
poll_interval = 30
# Path to the .pi_power status file
pi_power_file_path = '/home/pi/.pi_power_status'
power_source = 'unknown'
power_fraction = 1.0
GPIO.setup(led_pin['red'], GPIO.OUT)
GPIO.setup(led_pin['green'], GPIO.OUT)
# Read the .pi_power file at intervals and light the correct LED
while True:
# read the .pi_power status file
try:
with open(pi_power_file_path, "r") as f:
fields = f.read().rstrip().split(',')
power_fraction = float(fields[0])
power_source = fields[1]
except IOError:
# dummy statement to handle python indentation...
dummy = 1
GPIO.output(led_pin['red'], led_states['off'])
GPIO.output(led_pin['green'], led_states['off'])
if power_source == 'usb':
green_blink()
elif power_source == 'battery':
# Modify the colors and cutoff levels to suit your needs
if power_fraction >= 0.25:
green_constant()
# if you have an RGB LED try this instead
# yellow_constant()
elif power_fraction >= 0.15:
red_constant()
elif power_fraction >= 0.10:
red_blink()
else:
red_blink_fast()
else:
# Leave LEDs off - just sleep
time.sleep(poll_interval)