Scheduled shutdown of balenaSound on Pi 3B

Project help balenaSound
1

Hello:

I love the balenaSound project, but have a question about shutdown. I believe a useful feature would be the ability to shut the device down by itself, either after not playing audio for a preset time (configurable in the device variables section), or at a certain time of the day, like 4.00 am or something - again, configurable.

My Pi 3 has been through a few SD Cards where there has been a power failure, and this seems to have taken the card down - at least I assume that’s what’s going on. Shutting down this way will switch the device off gracefully, and save energy as well.

Thanks, and great project.

3

Hello Mike,

I’m new on the forum, but here are my thoughts.

If you have a multi docker environment, and define it via a docker-compose yaml file, you should be able interact with the supervisor via the host APIvia the local docker network.

See https://www.balena.io/docs/learn/develop/runtime/ for the environment variables you can use ( BALENA_SUPERVISOR_ADDRESS seems convenient). Be sure to also set the label io.balena.features.supervisor-api: '1' on the container where you want to implement the shutdown timer.

This resource https://www.balena.io/docs/reference/supervisor/supervisor-api/ gives an example command to shut down the hardware:

curl -X POST --header "Content-Type:application/json" \
    "$BALENA_SUPERVISOR_ADDRESS/v1/shutdown?apikey=$BALENA_SUPERVISOR_API_KEY"

We can wrap this in a python script for example and put it in it’s own container. Something that I quickly have thrown together:

import requests
import os
import re
from dateutil.relativedelta import relativedelta
import datetime

headers = {
    'Content-Type': 'application/json',
}

params = (
    ('apikey', os.getenv('BALENA_SUPERVISOR_API_KEY')),
)

nap_time = os.getenv('NAP_TIME')
match = re.match('(\d{1,2}):(\d{1,2})', nap_time)

if match is not None:
    hour = match.group[1]
    minute = match.group[2]

    today = datetime.date.today()
    nap_time_today = datetime.date(
        today.year, 
        today.month, 
        today.day,
        hour,
        minute
    )
    while (datetime.datetime.today() < nap_time_today):
        time.sleep(5)

    requests.post('http://{}/v1/shutdown'.format(os.getenv('BALENA_SUPERVISOR_ADDRESS')), headers=headers, params=params)

Then we can set the environment variable NAP_TIME to e.g.: 4:00 (or any 24-hour clock time) and the script should shut down the host.

I hope this brings you some inspiration.
Woody

1 Like
4

Hello Woody:

Thanks for your fast reply. I’ll have a go at this when I get a moment! Really appreciate this.

Mike.