Thermal eInk Selfie Photo Frame

Overview

In this project I built an Eink photo frame which takes thermal readings using a 32x24 temperature sensor and converts into a thermal image. You can take your selfies even in dark! After taking the image the power can be disconnected and the photo stays there. The step by step instructions are given below. I am using macOS as host machine. The instructions and commands can be adapted for other operating systems.

Install Raspberry Pi OS Lite

Download Raspberry Pi Imager from here: https://www.raspberrypi.org/software/ and install Raspberry Pi OS Lite.

Headless setup

We don't like to use the photo frame with monitor/keyboard/mouse!

$ cd /Volume/boot
$ touch ssh

Create a file wpa_supplicant.conf with following contents. Please change COUNTRY CODE, SSID, and PASSWORD according to your location. For example, for USA, country code is US.

ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1
country=<COUNTRY CODE>
network={
  ssid="SSID"
  psk="PASSWORD"
}

Login to Pi Zero W over SSH

After booting up we can ssh into it.

$ ssh pi@raspberrypi.local

Update the OS

This is optional but everyone likes updated OS!

$ sudo apt update
$ sudo apt upgrade

Enable SPI and I2C

The eInk display uses SPI and the thermal camera uses I2C connections. We can enable them using the Raspberry Pi configuration utility.

$ sudo raspi-config

Select Interface Options as shown below.

Choose SPI and I2C one by one and enable them in the next screen.

Connection

The Pi Zero is connected to the Inky Impression and the thermal camera as shown below.

Install Pimoroni Inky library

$ sudo apt install python3-pip
$ pip3 install inky[rpi,fonts]

Test connection

$ sudo apt install i2c-tools
$ i2cdetect -y 1

     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- 33 -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --

Build/Install MLX90640 C++ library

$ cd ~
$ git clone https://github.com/pimoroni/mlx90640-library.git
$ cd mlx90640-library
$ make clean
$ make I2C_MODE=LINUX
$ sudo make install

Build/Install MLX90640 Python bindings

$ sudo apt install swig
$ cd ~/mlx90640-library/python/library
$ make build
$ sudo make install

Configure I2C baud rate

Open /boot/config.txt and add the line below.

dtparam=i2c1_baudrate=400000

Build a photo frame

I am using an off-the-shelf photo frame backing board and just stuck behind the eInk display using a double-sided tape.

Demo

The button A at the top left of the display is configured as a photo capture button. After pressing the button the application waits for 5 seconds before capturing a frame.

Thanks for reading and watching!