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---
title: A stupid smart doorbell system
tags: [doorbell, debian, ssh, fswebcam, bash, shell, microphone, webcam, raspberry pi, thinkpad]
updated: 2018-11-06 23:00
description: A stupid smart doorbell that mails you a photo of who rang
---
A [smart doorbell](https://en.wikipedia.org/wiki/Smart_doorbell) is useful when
you are not at home but you want to be notified about when and who rang.
## Ideas
The idea behind my implementation is very naïve: someone rings at the
doorbell, a program listening from a microphone pics up the sound and triggers
a script. A webcam pointed in front of the door takes a picture which is sent
as an email attachment.
Initially I wanted to use a [cheap wireless
doorbell](https://harizanov.com/2013/07/raspberry-pi-emalsms-doorbell-notifier-picture-of-the-person-ringing-it/).
The problem is that I have no experience in soldering and I didn't want to
mess things up. However, the idea intreagued me nonetheless.
I had to find another system to get the trigger. The obvious way was to use
the existing doorbell system in the house. For this purpose I found a [ruby
script](http://thomer.com/howtos/detect_sound.html) which uses
[ALSA](https://www.alsa-project.org/main/index.php/Main_Page) and [soX](http://sox.sourceforge.net/)
to record and examine the sound. If the sound is greater than the set
threshold an external script is called. I added an expected frequency range
detection check which is useful to avoid some false positives. To do this I
first translated the script from ruby to bash.
## Hardware tests
The first thing I did was to try the Raspberry PI 3B plus, with a
an unnamed USB webcam which has an integrated microphone. A Logitech USB webcam
would take the pictures instead.
The Raspberry was connected via Ethernet. Unfortunately the single board
computer suffers from USB bandwidth problems since [the 4 USBs ports and the
Ethernet socket are all shared as part of a single
hub](https://raspberrypi.stackexchange.com/questions/44433/does-wifi-on-the-pi-3-reduce-the-ethernet-bottleneck-when-using-usb-device).
Just in case I also tried using a powered 7 port USB hub. The results were the
following:
Error starting stream. VIDIOC_STREAMON: Connection timed out
VIDIOC_DQBUF: Invalid argument
Capturing 1 frames...
VIDIOC_DQBUF: Invalid argument
No frames captured.
What follows is part of the output from `$ lsusb` concerning the previously
cited webcam.
ID 0c76:1600 JMTek, LLC. Ion Quick Play LP turntable
ID 1871:0306 Aveo Technology Corp.
Even using the integrated WiFi card, which is not connected to the USB hub,
didn't solve the problem. I had to use a proper computer...
With an old IBM Thinkpad everything seemed to work fine so I decided
to add another feature. Using the same unnamed webcam and the software
[motion](https://motion-project.github.io/) it is possible to detect movement.
I tried to use that to know when and who passes through the front door.
Just like before, there were problems with the USB bandwidth. A cause of this
might be that the computer has USB version 1.1 ports. I had slightly better
improvements when I passed from a USB microphone to an analog one and changed
the original webcam to an
ID 058f:3880 Alcor Micro Corp.
[But the bandwidth was still not
enough](https://motion-project.github.io/motion_config.html#basic_setup_v4l2),
so I had to settle for a simple doorbell system for the moment.
## Ingredients
What follows are a couple of tables of all the hardware and software ingredients I used.
### Hardware
| Object | Quantity | Description | Purpose | Required |
|:-------------:|:-------------:|:-----:|:
| [IBM ThinkPad A31](https://www.thinkwiki.org/wiki/Category:A31) | 1 | computer | control the devices and read sensors | yes |
| [Logitech QuickCam E1000](https://wikidevi.com/wiki/Logitech_HD_Pro_Webcam_C920#Models) | 1 | webcam | Take photos | yes |
| [Dlink DHP-306AV](https://eu.dlink.com/uk/en/products/dhp-306av-powerline-av-network-adapter) | 1 | powerline to ethernet adapters | if your computer is out of range from the router or switch | no |
| Ethernet wire | 2 | CAT 5e | connect the power line devices | no |
| USB extension cord | 1 | | connect this cable between the computer and the webcam | no |
| analog microphone | 1 | cheap microphone with a 3.5mm jack | record audio | yes |
| plastic cup | 1 | put this around the microphone tip and point it to the doorbell | concentrate the sound | no |
| paper tape | some | | stick the microphone to the wall near the doorbell | no |
### Software
| Software | Description | Required |
|----------|--------------|----------|
| [Debian](https://cdimage.debian.org/debian-cd/current/i386/iso-cd/debian-9.5.0-i386-netinst.iso) | i386 stable. Version 9.5.0. Operating system. I didn't want to fiddle too much this time | yes |
| [fswebcam](http://www.sanslogic.co.uk/fswebcam/) | take pictures | yes |
| [OpenSSH](https://www.openssh.com/) | configure the computer remotely | yes |
| [NTP](http://www.ntp.org/) | time synchronization daemon | yes |
| [S-nail]( http://www.sdaoden.eu/code.html#s-nail) | send mails | yes |
| [msmtp](https://marlam.de/msmtp) | MTA | yes |
| [soX](http://sox.sourceforge.net/) | sound processing | yes |
| [bc](https://www.gnu.org/software/bc/) | arithmetic comparisions in bash | yes |
| [ALSA](http://www.alsa-project.org) | set the audio levels | yes |
| [GNU Bash](http://www.gnu.org/software/bash/bash.html) | "The GNU Bourne Again shell" | yes |
| [eSpeak](http://espeak.sourceforge.net/) | speech synthesis | no |
| [Haveged](https://github.com/jirka-h/haveged) | "[...] Feed Linux's random device" | no |
| [webfs](http://linux.bytesex.org/misc/webfs.html) | a simple web server so you can access the pictures with in a simple manner | no |
## Scripts
What follows are the two scripts I used, called `listen.sh` and `shoot.sh`
respectively.
```shell
#!/bin/bash
#
# listen.sh
#
# Copyright (C) 2009 Thomer M. Gil [http://thomer.com/]
# 2018 Franco Masotti
#
# Oct 22, 2009: Initial version
# Oct 29, 2018: Translation from ruby to bash. Added expected frequency range.
#
# This program is free software. You may distribute it under the terms of
# the GNU General Public License as published by the Free Software
# Foundation, version 2.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
# Public License for more details.
#
# This program detects the presence of sound and invokes a program.
#
# You need to replace MICROPHONE with the name of your microphone, as reported
# by /proc/asound/cards.
MICROPHONE='I82801CAICH3'
# Sampling format of the audio card.
FORMAT='S16_LE'
THRESHOLD='0.30'
# Expected frequencies in Hz.
EXPECTED_FREQ_MIN='600'
EXPECTED_FREQ_MAX='1250'
# Sample gathering in seconds.
SAMPLE_DURATION='3'
SCRIPT_FULL_PATH="/home/doorbell/srv_maint/scripts/doorbell/shoot.sh"
HWDEVICE="$(cat /proc/asound/cards | grep "${MICROPHONE}" | awk '{print $1}')"
while true; do
out="$(/usr/bin/arecord -D plughw:"${HWDEVICE}",0 -d "${SAMPLE_DURATION}" \
-f "${FORMAT}" 2>/dev/null | /usr/bin/sox -t .wav - -n stat 2>&1)"
# As you can see, no regex are used here -> this might fail.
amplitude="$(echo "${out}" | grep 'Maximum amplitude' | awk '{print $3}')"
frequency="$(echo "${out}" | grep 'Rough frequency' | awk '{print $3}')"
if [ "$(echo ""${amplitude}">="${THRESHOLD}"" | bc -l)" -eq 1 ]; then
if [ "$(echo ""${frequency}">="${EXPECTED_FREQ_MIN}"" | bc -l)" -eq 1 ] \
&& [ "$(echo ""${frequency}"<="${EXPECTED_FREQ_MAX}"" | bc -l)" -eq 1 ]; then
echo "match: f=${frequency} Hz; a=${amplitude}"
${SCRIPT_FULL_PATH}
else
echo "no match: f=${frequency} Hz; a=${amplitude}"
fi
else
echo "no match: a=${amplitude}"
fi
done
```
```shell
#!/bin/bash
#
# shoot.sh
#
# Copyright (C) 2018 Franco Masotti
#
# Oct 29, 2018: Initial version.
#
# This program is free software. You may distribute it under the terms of
# the GNU General Public License as published by the Free Software
# Foundation, version 2.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
# Public License for more details.
#
# This program takes a picture and sends it via mail.
#
BASE_DIR="/home/doorbell/srv_maint/scripts/doorbell"
PICTURE_FILE="/var/www/doorbell.jpg"
MESSAGE="event: $(date +"%F %T")"
CAMERA="/dev/video0"
RESOLUTION="640x480"
CAPTURE_FRAMES="1"
SKIP_FRAMES="50"
BRIGHNESS="100%"
CONTRAST="100%"
LOG_FILE="/var/log/doorbell.log"
MAIL_SUBJECT="doorbell"
MAIL_SENDER="Home"
MAIL_RECEIVER_ALIAS="all"
pushd "${BASE_DIR}"
fswebcam \
--set brightness="${BRIGHTNESS}" \
--set contrast="${CONTRAST}" \
-r "${RESOLUTION}" \
-R \
--font 'dejavu:10' \
-S "${SKIP_FRAMES}" \
-F "${CAPTURE_FRAMES}" \
-d v4l2:"${CAMERA}" "${PICTURE_FILE}" &
pid="$!"
# Below: put generic commands.
# Speak out.
espeak -s 125 -v it "Campanello" &
# Keep a log file.
echo "${MESSAGE}" >> "${LOG_FILE}" &
# Wait for the picture to be taken.
wait "${pid}"
# Below: put commands which need the photo as dependency.
echo "${MESSAGE}" | s-nail \
-r "${MAIL_SENDER}" \
-s "${MAIL_SUBJECT}" \
-a "${PICTURE_FILE}" \
"${MAIL_RECEIVER_ALIAS}" &
popd
```
## Instructions
### Installation
- Configure the network in `/etc/network/interfaces`
- Install the software
```
# apt-get update
# apt-get dist-upgrade
# apt-get install alsa-utils fswebcam openssh ntp s-nail msmtp sox bc alsa-utils bash espeak haveged webfs
```
- Add a user and its password
```
# useradd -m -s /bin/bash doorbell
# passwd doorbell
# exit
```
- Login with the newly created user and copy the scripts
```
$ mkdir ~/srv_maint/scripts/doorbell
$ cp listen.sh shoot.sh ~/srv_maint/scripts/doorbell
```
- Add a cron entry so that the scripts runs automatically at every boot.
```
$ echo "@reboot /home/doorbell/srv_maint/scripts/doorbell/listen.sh" > ~/srv_maint/cron_entries.txt
$ crontab ~/srv_maint/cron_entries.txt
```
- Touch and prepare the log file
```
# touch /var/log/doorbell.log
# chown doorbell:doorbell /var/log/doorbell.log
```
- [Configure the mail system](https://wiki.archlinux.org/index.php/Msmtp#Using_the_mail_command). See [this](https://wiki.archlinux.org/index.php/Msmtp#Using_msmtp_offline) also.
- Configure webfs in `/etc/webfsd.conf`. Once everything is set up you may
run the shoot.sh script and `$ wget http://<doorbell_computer_address>/doorbell.jpg`
```
# debian config file for webfsd. It is read by the start/stop script.
# document root
web_root="/var/www"
# hostname (default to the fqdn)
web_host=""
# ip address to bind to (default: any)
web_ip=""
# port to listen on (default: 8000)
web_port="80"
# virtual host support (default: false)
web_virtual="false"
# network timeout (default: 60 seconds)
web_timeout=""
# number of parallel connections (default: 32)
web_conn=""
# index file for directories (default: none, webfsd will send listings)
web_index=""
# size of the directory cache (default: 128)
web_dircache=""
# access log (common log format, default: none)
web_accesslog=""
# use bufferred logging (default: true)
web_logbuffering="true"
# write start/stop/errors to the syslog (default: false)
web_syslog="false"
# user/group to use
web_user="www-data"
web_group="www-data"
# cgi path (below document root -- default: none)
web_cgipath=""
# extra options, including arguments
web_extras=""
```
#### Calibration
- Use `$ alsamixer` to set the audio levels. The hardest part was finding a
working interval for the amplitude and frequency values through which the
script is able to avoid as much false positives as possible.
- [Fix the desired audio level for the next reboots](https://unix.stackexchange.com/questions/210113/default-sound-volume-for-all-alsa-devices)
```
# alsactl store
```
## Possible roadmeap
- Version 0.0: this version.
- Version 0.1: discontinue the Thinkpad A31 and use the Raspberry PI instead
with an (full HD?) IR camera module and its extension cord to reach out of
the door. This should free the USB hub that we must use for the audio
trigger (a usb microphone or USB audio card connected to the analog
microphone).
- Version 0.2: instead of using an audio trigger, use some kind of sensor. Our
doorbell transforms the electrical current to piston movement against two
metal bars that vibrate at a certain frequency, which in turn produce
sound. This new yet unkown method should always be reliable and avoid any
false positive.
- Version 0.3: add an open-close door sensor which interfaces to the GPIO. Use
a USB camera once this trigger activates.
- Version 0.4: adapt all this stuff so that it works with something like [Home
Assistant](https://www.home-assistant.io/) or [Kalliope](https://kalliope-project.github.io/).
~
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