ESP32 E-Paper Weather Display

NOTICE: This article contains some out-of-date information. For up-to-date information and instructions please refer to this project's github page. https://github.com/lmarzen/esp32-weather-epd

This is a weather display powered by a wifi-enabled ESP32 microcontroller and a 7.5in E-Paper (aka E-ink) display. Current and forecasted weather data is obtained from the OpenWeatherMap API. A sensor provides the display with accurate indoor temperature and humidity.

The project draws ~14μA when sleeping and an estimated average of ~83mA during its ~10s wake period. The display can be configured to update as frequently as desired. When the refresh interval is set to 30 minutes, the device will run for >6 months on a single 5000mAh battery. The project displays accurate battery life percentage and can be recharged via a USB-C cable connected to a wall adapter or computer.

There are configuration options for everything from location, time/date formats, units, and language to air quality index scale and hourly outlook graph bounds.

The hourly outlook graph (bottom right) shows a line indicating temperature and shaded bars indicating probability of precipitation.

About the Stand

I made a small stand by hollowing out a piece of wood from the bottom. On the back, I used a short USB extension cable so that I can charge the battery without needing to remove the components from the stand. I also wired a small reset button to refresh the display manually. Additionally, I 3d printed a cover for the bottom, which is held on by magnets. The E-paper screen is very thin, so I used a thin piece of acrylic to support it.

Hardware

7.5inch (800×480) E-Ink Display w/ HAT for Raspberry Pi, SPI interface

• Advantages of E-Paper
• Ultra Low Power Consumption - E-Paper (or E-Ink) displays are ideal for low-power applications that do not require frequent display refreshes. E-Paper displays only draw power when refreshing the display and do not have a backlight. Images will remain on the screen even when power is removed.
• Limitations of E-Paper:
• Colors - E-Paper has traditionally been limited to just black and white, but in recent years 3-color E-Paper screens have started showing up.
• Refresh Times and Ghosting - E-Paper displays are highly susceptible to ghosting effects if refreshed too quickly. To avoid this, E-Paper displays often take a few seconds to refresh(4s for the unit used in this project) and will alternate between black and white a few times, which can be distracting.
• https://www.waveshare.com/product/7.5inch-e-paper-hat.htm (800x480, 7.5inch E-Ink display, Black/White)
• Note that this project also now supports this 3-color panel as well, though the program will only draw black/white to the screen. https://www.waveshare.com/product/7.5inch-e-paper-hat-b.htm (800x480, 7.5inch E-Ink display, Red/Black/White)

FireBeetle 2 ESP32-E Microcontroller

Why the ESP32?

• Onboard WiFi
• 520kB of RAM and 4MB of FLASH, enough to store lots of icons and fonts.
• Low power consumption.
• Small size, many small development boards available.

Why the Firebeetle 2 ESP32-E

• Drobot's FireBeetle ESP32 models are optimized for low-power consumption (https://diyi0t.com/reduce-the-esp32-power-consumption/). The Drobot's FireBeetle 2 ESP32-E variant offers USB-C, but older versions of the board with Mirco-USB would work fine too.
• Firebeelte ESP32 models include onboard charging circuitry for a 3.7v lithium-ion(LiPo) battery.
• FireBeetle ESP32 models include onboard circuitry to monitor battery voltage of a battery connected to its JST-PH2.0 connector.
• https://www.dfrobot.com/product-2195.html

BME280 - Pressure, Temperature, and Humidity Sensor

• Provides accurate indoor temperature and humidity.
• Much faster than the DHT22, which requires a 2-second wait before reading temperature and humidity samples.

3.7V Lipo Battery w/ 2 Pin JST Connector

• Size is up to you. I used a 5000mah battery so that the device can operate on a single charge for >6 months. (Maybe longer, time will tell)
• The battery can be charged by plugging the FireBeetle ESP32 into the wall via the USB-C connector while the battery is plugged into the ESP32's JST connector.

WARNING: The polarity of JST-PH2.0 connectors is not standardized! You may need to swap the order of the wires in the connector.

Wiring

Pin connections are defined in config.cpp.

If you are using the FireBeetle 2 ESP32-E, you can use the connections I used or change them how you would like.

IMPORTANT: The E-Paper Driver Hat has two physical switches that MUST be set correctly for the display to work.

• Display Config: Set switch to position B.
• Interface Config: Set switch to position 0.

Cut the low power pad for even longer battery life.

• From https://wiki.dfrobot.com/FireBeetle_Board_ESP32_E_SKU_DFR0654

Low Power Pad: This pad is specially designed for low power consumption. It is connected by default. You can cut off the thin wire in the middle with a knife to disconnect it. After disconnection, the static power consumption can be reduced by 500 μA. The power consumption can be reduced to 13 μA after controlling the maincontroller enter the sleep mode through the program. Note: when the pad is disconnected, you can only drive RGB LED light via the USB Power supply.

Code

Please see the github repository for up-to-date information and instructions on how to configure, compile, and upload the code to esp32: https://github.com/lmarzen/esp32-weather-epd

This is an open source project (see github for licensing).

PlatformIO for VSCode is used for managing dependencies, code compilation, and uploading to ESP32.

OpenWeatherMap API Key

Sign up here to get an API key; it's free. https://openweathermap.org/api

This project will make calls to 2 different APIs ("One Call" and "Air Pollution").

NOTE: OpenWeatherMap One Call 2.5 API has been deprecated for all new free users (accounts created after Summer 2022). Fortunately, you can make 1,000 calls/day to the One Call 3.0 API for free by following the steps below.

• If you have an account created before Summer 2022, you can simply use the One Call 2.5 API by changing OWM_ONECALL_VERSION = "2.5"; in config.cpp.
• Otherwise, the One Call API 3.0 is only included in the "One Call by Call" subscription. This separate subscription includes 1,000 calls/day for free and allows you to pay only for the number of API calls made to this product.

Here's how to subscribe and avoid any credit card changes:

• Go to https://home.openweathermap.org/subscriptions/billing_info/onecall_30/base?key=base&service=onecall_30
• Follow the instructions to complete the subscription.
• Go to https://home.openweathermap.org/subscriptions and set the "Calls per day (no more than)" to 1,000. This ensures you will never overrun the free calls.