It is helpful to check my schedule with a calendar at any time. All I have to do is open Google Calendar on my phone or PC, but I would like to see it with less effort.

Google Nest Hub and Amazon Echo Show are a little different from what I want, and I cannot also find other devices. So I tried to create a calendar connected to Google via API using Raspberry Pi and e-paper.

Procedure

1. Get my schedule data from Google Calendar via API
2. Generate the image of the calendar showing my schedule
3. Get the e-paper
4. Display the image on the e-paper

Software

Occasionally I find the example to implement, so I also use Python.

Please check out my GitHub repository if you just want to see implementation.

Create the project directory

// create the project directory
$ poetry new my-project
// initialize configuration if the directory exist
$ poetry init
// add packages
$ poetry add google-api-python-client google-auth-httplib2 google-auth-oauthlib pillow

Install the packages to authenticate with my Google account, fetch data from Google Calendar, and generate the calendar image.

Fetch the event data from Google Calendar

Fetch data using the Google Calendar API. The basic usage of this API is described in the article below:

I would like to implement the following specification:

• Begin on Sunday and end on Saturday
• Display Sunday and public holidays in Japan in red color
• Mark the day that I have a plan
• Show the list of my schedule about the date and the detail of it in the future

An authentication file is required to connect to Google Calendar. If credentials.json file exists, authentication is required the first time the script is run. Once authenticated, token.pickle file is generated and can be used to authenticate with this file from then on.

Raspberry Pi Zero WH has low processing performance, making it difficult to open a browser and authenticate. So it is better to generate token.pickle file on another PC and transfer it to the Raspberry Pi via SCP.

Generating the image

There are some major libraries to process the image. I use Pillow (PIL) this time.

Sample implementation is published at GitHub.

• connect_calendar.py: fetch the data from Google Calendar
• main.py: generate the image of the calendar and control the e-paper

Note that these programs is optimized for Japanese calendar.

It is slightly more difficult to align the text. It is better to use multiline_textbbox to get the size of the outer frame of the text and align it.

How to get the e-paper

In this time, I purchased e-paper, which is relatively large in size, from Waveshare Electronics.

E-paper 640x384

I prepared some devices and accessories.

• Waveshare 7.5inch HD (880x528) e-paper black/red/white (B)
• Raspberry Pi Zero WH
• microSD 16GB
• miniHDMI to HDMI Adapter
• microUSB Hub

The e-paper was delivered from Shenzhen after about 10 days when I ordered.

Prepare the Raspberry Pi

I chose Zero WH model because high performance was not necessary. "W" means to be available for Wi-Fi and "H" means to be with the header pin. "W" means available for Wi-Fi and "H" means with the header pin.

Raspberry Pi Zero WH

In order to control Raspberry Pi, it is necessary to install Raspberry Pi OS (Raspbian before) on the microSD card with Raspberry Pi Imager.

After that, insert the microSD card into Raspberry Pi and power it up to connect a power cable to the "PWR IN" port. If you would like to shut it down, run the following command:

$ shutdown -h now

Security

It is necessary to change the default configuration not to attack from out of the local network.

First, create new user and add the permissions.

$ sudo passwd root
$ sudo adduser USERNAME
$ groups pi
$ sudo usermod -G pi,adm,dialout,cdrom,sudo,audio,video,plugdev,games,users,input,netdev,spi,i2c,gpio,lpadmin USERNAME
$ groups USERNAME
$ sudo cp -r /home/pi/* /home/USERNAME

Next, delete the default user. I couldn't select the default user because it was enabled to log in automatically in the initial configuration.

$ sudo raspi-config

Run the above command and disable it using System Options > Boot / Auto Login > Console. When the setting is complete, reboot the device.

$ sudo reboot

After the reboot, log in with new user and password, and delete the default user.

$ sudo userdel -r pi
$ id -a pi
id: 'pi': no such user

Enable the GUI using System Options > Boot/Auto Login > Desktop. Note that automatic login remains disabled.

$ sudo raspi-config

Finally, reboot again.

$ sudo reboot

Enable SSH

Enable SSH (port 22) using Interface Options > SSH.

$ sudo raspi-config

Check local IP address to connect Raspberry Pi from the same local network with the following command:

$ ping raspberrypi.local

Enable SPI

Enable SPI to control the e-paper using Interface Options > SPI > enable.

$ sudo raspi-config
$ sudo reboot

Install the packages to use Python. (Almost of all was already installed.)

$ sudo apt-get update
$ sudo apt-get install python3-pip
$ sudo apt-get install python3-pil
$ sudo apt-get install python3-numpy
$ sudo pip3 install RPi.GPIO
$ sudo pip3 install spidev

It seems that it is not necessary for BCM2835 and WiringPi library when implementing the program with Python.

Test

Run the demo program prepared by Waveshare.

$ sudo apt-get install git
$ git clone https://github.com/waveshare/e-paper.git
$ cd ./e-paper/RaspberryPi_JetsonNano/python/examples
$ python epd_7in5b_HD_test.py

Implementation

The default Python is an old version. Prepare the virtual environment so as not to break the default one.

Note that it takes very long time to install some packages into Zero WH.

// install pyenv
$ git clone https://github.com/pyenv/pyenv.git ~/.pyenv
$ echo 'export PYENV_ROOT="$HOME/.pyenv"' >> ~/.bashrc
$ echo 'export PATH="$PYENV_ROOT/bin:$PATH"' >> ~/.bashrc
$ echo -e 'if command -v pyenv 1>/dev/null 2>&1; then\n  eval "$(pyenv init -)"\nfi' >> ~/.bashrc

// install poetry
$ curl -sSL https://raw.githubusercontent.com/python-poetry/poetry/master/get-poetry.py | python -

Install the appropriate version of Python using pyenv.

$ sudo apt-get install -y build-essential libssl-dev zlib1g-dev libbz2-dev \
libreadline-dev libsqlite3-dev wget curl llvm libncurses5-dev libncursesw5-dev \
xz-utils tk-dev libffi-dev liblzma-dev python-openssl git
$ pyenv install 3.9.0

Install the required package at the same time not to fail to install Pillow package.

Reference：# Building on Linux | Installation - Pillow

$ sudo apt-get install libtiff5-dev libjpeg8-dev libopenjp2-7-dev zlib1g-dev \
    libfreetype6-dev liblcms2-dev libwebp-dev tcl8.6-dev tk8.6-dev python3-tk \
    libharfbuzz-dev libfribidi-dev libxcb1-dev

Create the virtual environment under the project directory.

$ poetry config virtualenvs.in-project true --local

PYTHONPATH=.venv

Poetry installs almost all the necessary packages, but it is not included that only use in Raspberry Pi.

$ git clone https://github.com/mktia/e-calendar.git && cd ./e-calendar
$ pyenv local 3.9.0
$ poetry install
$ pip3 install RPi.GPIO
$ pip3 install spidev

Auto update of the calendar

Enable cron

Enable the logs that crontab uses.

$ sudo vi /etc/rsyslog.conf

###############
#### RULES ####
###############

#
# First some standard log files.  Log by facility.
#
auth,authpriv.*                 /var/log/auth.log
*.*;auth,authpriv.none          -/var/log/syslog
// uncomment
cron.*                          /var/log/cron.log

$ sudo /etc/init.d/rsyslog restart

Create the file to record the logs.

$ sudo touch /var/log/e-calendar.log
$ sudo chmod 777 /var/log/e-calendar.log

And, check the status of cron service.

$ sudo /etc/init.d/cron status
● cron.service - Regular background program processing daemon
   Loaded: loaded (/lib/systemd/system/cron.service; enabled; vendor preset: enabled)
   Active: active (running) since Fri 2021-03-19 14:17:29 JST; 3h 11min ago
     Docs: man:cron(8)
 Main PID: 262 (cron)
    Tasks: 1 (limit: 877)
   CGroup: /system.slice/cron.service
           └─262 /usr/sbin/cron -f

If cron.service is disabled, run the start command.

Crontab configuration

Edit the crontab using the following command:

$ crontab -e

Note that the environment variables are not used because it doesn't run the shell as a user.

First, prepare the script file.

$ touch ~/e-calendar.sh
$ sudo chmod 755 ~/e-calendar.sh
$ nano ~/e-calendar.sh

#!/bin/bash

SHELL=/bin/bash
PYENV_ROOT=$HOME/.pyenv
POETRY_ROOT=$HOME/.poetry
PATH=$PYENV_ROOT/bin:$POETRY_ROOT/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

if command -v pyenv 1>/dev/null 2>&1; then
  eval "$(pyenv init -)"
fi

cd ~/e-calendar
$POETRY_ROOT/bin/poetry run python main.py

Next, add the command to run the script every hour to the crontab.

0 * * * * /home/USERNAME/e-calendar.sh > /var/log/e-calendar.log 2>&1

With the above settings, the log is overwritten each time it is run with the above settings.

As a desk calendar

To use e-paper as a desk calendar, it would be better to use a photo frame.

GitHub: mktia/e-calendar