More Clever Night Light

The night light of my kid has:

a clock that diverges quite fast: 1 minute per week,
no memory of the program: I need to enter the program again after a power outage (and no battery backup),
no way to program several hours: for school days and holidays,

an annoying UX :

But it is quite good looking.

Let’s use its casing to build something that does not have those disadvantages.

I want to have a device that is in general disconnected from the wifi, but that connects for a few minutes every day to fetch the current time.

As it happens, I have an unused raspberry pi 1B that could do the trick. I could later use a smaller devices, like a ESP8266 based board in the future, but that is a story for another time.

lights

first idea -> using the gpio to power a few leds

That will result in a lot of wires, and I’m an not sure that I will have enough brightness.

second idea -> use a extra neopixel from my IOT heart project

It looks like it is quite simple according to https://learn.adafruit.com/neopixels-on-raspberry-pi/overview

On the raspberry pi 1B, it seems like there is only one pin to deal with pwm, the 18. Hence I suppose I need to follow the advice of disabling the sound¹.

ssh bayberry sudo sed -i 's/dtparam=audio=on/dtparam=audio=off/' /boot/config.txt

debugging

need to run in privileged mode

I should be able to run it this way:

docker run --device /dev/mem --device /dev/gpiomem --device /dev/vcio --rm -ti konubinix/neopixel /app/venv/bin/ipython

But somehow, it does not.

Until I fix the line above, let’s simply use the privileged mode.

docker run --privileged --rm -ti konubinix/neopixel /app/venv/bin/ipython

the code

It did not need a lot of iteration to find out the code I wanted.

light on

Lighting on the neopixel is as simple as this:

#!/usr/bin/env python3
# -*- coding:utf-8 -*-

import board
import neopixel
import requests
from datetime import datetime

def main():
    pixels = neopixel.NeoPixel(board.D18, 1)
    pixels[0] = (255, 255, 255)
    print("On")
    requests.post("http://192.168.1.46:9705/nightlight", headers={"Title": "nightlight", "priority": "min"}, data=f"{datetime.now()}: On")

if __name__ == "__main__":
    main()

The http post here is using ntfy to tell me that everything went well.

light off

And, of course the code of the lightoff program is the same with off instead of on.

#!/usr/bin/env python3
# -*- coding:utf-8 -*-

import board
import neopixel
import requests
from datetime import datetime

def main():
    pixels = neopixel.NeoPixel(board.D18, 1)
    pixels[0] = (0, 0, 0)
    print("Off")
    requests.post("http://192.168.1.46:9705/nightlight", headers={"Title": "nightlight", "priority": "min"}, data=f"{datetime.now()}: Off")

if __name__ == "__main__":
    main()

Most likely your intuition shouted that this code MUST be refactored. Take a deep breath, think about something relaxing, and you should be good to continue reading this.

almost time

If the lights were only binary, my kid would not want to wait until the light gets on. Per need some way to say “it is almost time, wait a little bit longer”.

Without surprise, this is the same code, with another color.

#!/usr/bin/env python3
# -*- coding:utf-8 -*-

import board
import neopixel
import requests
from datetime import datetime

def main():
    pixels = neopixel.NeoPixel(board.D18, 1)
    pixels[0] = (0, 30, 40)
    print("Almost")
    requests.post("http://192.168.1.46:9705/nightlight", headers={"Title": "nightlight", "priority": "min"}, data=f"{datetime.now()}: Almost")

if __name__ == "__main__":
    main()

scheduling the changes

I will use cron to run the code. It needs to start the wifi (to send the notification), run the code and shut the wifi down. I actually decided to call the same program 5 times with 1 minute interval. I realized that in some rare occasions, the light did not change. I think the odds that the program fails 5 times in a row are very low.

# m      h      dom  mon  dow              command
# on school days
29     6      *    *    mon,tue,thu,fri  { date && rfkill unblock wlan ; } >> /var/log/cronlog/log.txt 2>&1
30-35  6      *    *    mon,tue,thu,fri  { date && /app/venv/bin/python /app/lightalmost.py ; } >> /var/log/cronlog/log.txt 2>&1
36     6      *    *    mon,tue,thu,fri  { date && rfkill block wlan ; } >> /var/log/cronlog/log.txt 2>&1

59     6      *    *    mon,tue,thu,fri  { date && rfkill unblock wlan ; } >> /var/log/cronlog/log.txt 2>&1
0-5    07     *    *    mon,tue,thu,fri  { date && /app/venv/bin/python /app/lighton.py ; } >> /var/log/cronlog/log.txt 2>&1
6      7      *    *    mon,tue,thu,fri  { date && rfkill block wlan ; } >> /var/log/cronlog/log.txt 2>&1

14     7      *    *    mon,tue,thu,fri  { date && rfkill unblock wlan ; } >> /var/log/cronlog/log.txt 2>&1
15-19  7      *    *    mon,tue,thu,fri  { date && /app/venv/bin/python /app/lightoff.py ; } >> /var/log/cronlog/log.txt 2>&1
20     7      *    *    mon,tue,thu,fri  { date && rfkill block wlan ; } >> /var/log/cronlog/log.txt 2>&1

# on not school days
29     7      *    *    wed,sat,sun      { date && rfkill unblock wlan ; } >> /var/log/cronlog/log.txt 2>&1
30-35  7      *    *    wed,sat,sun      { date && /app/venv/bin/python /app/lightalmost.py ; } >> /var/log/cronlog/log.txt 2>&1
36     7      *    *    wed,sat,sun      { date && rfkill block wlan ; } >> /var/log/cronlog/log.txt 2>&1

59     7      *    *    wed,sat,sun      { date && rfkill unblock  wlan ; } >> /var/log/cronlog/log.txt 2>&1
0-5    8      *    *    wed,sat,sun      { date && /app/venv/bin/python /app/lighton.py ; } >> /var/log/cronlog/log.txt 2>&1
6      8      *    *    wed,sat,sun      { date && rfkill block wlan ; } >> /var/log/cronlog/log.txt 2>&1

29     8      *    *    wed,sat,sun      { date && rfkill unblock wlan ; } >> /var/log/cronlog/log.txt 2>&1
30-35  8      *    *    wed,sat,sun      { date && /app/venv/bin/python /app/lightoff.py ; } >> /var/log/cronlog/log.txt 2>&1
36     8      *    *    wed,sat,sun      { date && rfkill block wlan ; } >> /var/log/cronlog/log.txt 2>&1

# get back online for a short time from time to time to be able to sync back the clock
00     12-22  *    *    *                { date && rfkill unblock wlan ; } >> /var/log/cronlog/log.txt 2>&1
02     12-22  *    *    *                { date && rfkill block wlan ; } >> /var/log/cronlog/log.txt 2>&1

This changes a little bit when the kids are in holiday. I don’t need to wake them up too early then.

# m      h      dom  mon  dow              command
# on not school days
29     7      *    *    *                { date && rfkill unblock wlan ; } >> /var/log/cronlog/log.txt 2>&1
30-35  7      *    *    *                { date && /app/venv/bin/python /app/lightalmost.py ; } >> /var/log/cronlog/log.txt 2>&1
36     7      *    *    *                { date && rfkill block wlan ; } >> /var/log/cronlog/log.txt 2>&1

59     7      *    *    *                { date && rfkill unblock  wlan ; } >> /var/log/cronlog/log.txt 2>&1
0-5    8      *    *    *                { date && /app/venv/bin/python /app/lighton.py ; } >> /var/log/cronlog/log.txt 2>&1
6      8      *    *    *                { date && rfkill block wlan ; } >> /var/log/cronlog/log.txt 2>&1

29     8      *    *    *                { date && rfkill unblock wlan ; } >> /var/log/cronlog/log.txt 2>&1
30-35  8      *    *    *                { date && /app/venv/bin/python /app/lightoff.py ; } >> /var/log/cronlog/log.txt 2>&1
36     8      *    *    *                { date && rfkill block wlan ; } >> /var/log/cronlog/log.txt 2>&1

# get back online for a short time from time to time to be able to sync back the clock
00     12-22  *    *    *                { date && rfkill unblock wlan ; } >> /var/log/cronlog/log.txt 2>&1
02     12-22  *    *    *                { date && rfkill block wlan ; } >> /var/log/cronlog/log.txt 2>&1

starting the container

My raspberry pi is called bayberry and I will control it using ssh.

Let’s provide some room to gather the logs to see if something goes wrong.

ssh bayberry mkdir -p /home/sam/cronlog

Then, the command to start the container is this one:

ssh bayberry docker run --pull always --detach --name nightlight --network host --restart always --privileged --volume /home/sam/cronlog/:/var/log/cronlog/ -ti konubinix/nightlight crond -f -L /var/log/cronlog/cron.log -l 6

It is a bit hairy, but there is nothing out of the ordinary here.

In case I need to refresh the container, I need to stop it beforehand, using that command.

play with it despite its offline state

Once started, it will mostly be offline. So you will need to power off and on again the device to be able to interact with it.

To restore the wlan at startup, I needed to add a command in the host

cat<<EOF | ssh bayberry sudo tee /etc/rc.local
#!/bin/sh -e
#
# rc.local
#
# This script is executed at the end of each multiuser runlevel.
# Make sure that the script will "exit 0" on success or any other
# value on error.
#
# In order to enable or disable this script just change the execution
# bits.
#
# By default this script does nothing.

rfkill unblock wlan

exit 0
EOF

fetching the logs of cron

Simply run

ssh bayberry cat cronlog/cron.log

manually playing with the lights

To light on, I can simply execute

ssh bayberry docker exec nightlight /app/venv/bin/python /app/lighton.py

get an interactive shell (useful to debug)

it is as simple as

ssh -t bayberry docker exec -ti nightlight ipython

hardware setup

Simply drilling a hole into the back of the device

Insert the led strip. And that’s all.

Now, reinstall it

And the magic happens

change the scheduling

I can edit the schedule manually, using

ssh -t bayberry docker exec -ti nightlight crontab -e

Or, to switch from holiday to school days crontabs, I simply can run

ssh bayberry docker exec nightlight crontab /home/sam/crontab

Check that the crontab is appropriately changed with

ssh bayberry docker exec nightlight crontab -l

# m      h      dom  mon  dow              command
# on not school days
29     7      *    *    *                { date && rfkill unblock wlan ; } >> /var/log/cronlog/log.txt 2>&1
30-35  7      *    *    *                { date && /app/venv/bin/python /app/lightalmost.py ; } >> /var/log/cronlog/log.txt 2>&1
36     7      *    *    *                { date && rfkill block wlan ; } >> /var/log/cronlog/log.txt 2>&1

59     7      *    *    *                { date && rfkill unblock  wlan ; } >> /var/log/cronlog/log.txt 2>&1
0-5    8      *    *    *                { date && /app/venv/bin/python /app/lighton.py ; } >> /var/log/cronlog/log.txt 2>&1
6      8      *    *    *                { date && rfkill block wlan ; } >> /var/log/cronlog/log.txt 2>&1

29     8      *    *    *                { date && rfkill unblock wlan ; } >> /var/log/cronlog/log.txt 2>&1
30-35  8      *    *    *                { date && /app/venv/bin/python /app/lightoff.py ; } >> /var/log/cronlog/log.txt 2>&1
36     8      *    *    *                { date && rfkill block wlan ; } >> /var/log/cronlog/log.txt 2>&1

# get back online for a short time from time to time to be able to sync back the clock
00     12-22  *    *    *                { date && rfkill unblock wlan ; } >> /var/log/cronlog/log.txt 2>&1
02     12-22  *    *    *                { date && rfkill block wlan ; } >> /var/log/cronlog/log.txt 2>&1

Notes linking here

“utiliser un marteau piqueur pour enfoncer un clou”

Permalink

Sound must be disabled to use GPIO18. This can be done in /boot/config.txt by changing “dtparam=audio=on” to “dtparam=audio=off” and rebooting. Failing to do so can result in a segmentation fault.

— https://learn.adafruit.com/neopixels-on-raspberry-pi/python-usage

↩︎