AQI

E-paper interfacing circuit is just a simple switched-mode power supply — Interfacing to E-paper displays is nothing to be scared of

[Aduecho] had seen those cheap eBay deals of e-paper-based pricing tags, and was wondering if they could be hacked to perform some other tasks. After splitting the case open, the controller chip was discovered to be a SEM9110, with some NFC hardware support but little else. [aduecho] was hoping to build some IoT-connected air quality indicator (AQI) units but the lack of a datasheet for SEM9110 plus no sensors in place meant the only real course of action was to junk the PCB and just keep the E-paper display and the batteries. These units appeared to be ‘new old’ stock, so there was a good chance that both would be fresh and ripe for picking.

The PCB [aduecho] came up with is mechanically the same as the original unit, but now sports a Seeed studio Wio-E5 LoRa module, which uses the STM32WLE5 from ST for the heavy lifting. This has what looks like a Semtech SX126x integrated on-die (we can’t think of a sane way an actual SX126x die could be flip-chip mounted, but you never know). Using this module is a snap, needing only very minimal antenna-matching components and a spot of decoupling to function. On the sensing side of things, a Bosch BME680 gas sensor handling the AQI measurements, and a Bosch BMI270 6-axis IMU, provides a gyro and accelerometer, for all those planned user interaction features. As can be seen from the schematic, interfacing the EPD is pretty straightforward, just a handful of parts are needed to generate the necessary bipolar gate voltages via a simple SMPS circuit. The display controller handles it all internally, programmed via an SPI interface.

One area we’re quite fond of in this project are the neat hand-drawn icons, and variable width font, giving the display a kind of note-like quality when drawn on the low-ish contrast e-paper display.

Air quality measurement projects grace these pages from time to time, like this hacked Ikea Vindriktning, and this very similar Wio-E5-based project we covered last month.

Air Quality Index for one’s region can be a handy thing to know, but it’s such a dry and humorless number, isn’t it? Well, all that changes with [Andrew Kleindolph]’s AQI Funnies: a visual representation of live AQI data presented by a friendly ghost character in a comic panel presentation. The background, mood, and messaging are all generated to match the current conditions, providing some variety (and random adjectives) to spruce things up.

We love the attention paid to the super clean presentation, and the e-paper screen looks fantastic. Inside the unit is a Raspberry Pi using Python to talk to the AirNow.gov API to get local conditions and update every four hours (AirNow also has a number of useful-looking widgets, for those interested.)

The enclosure is 3D printed, and [Andrew] uses a Witty Pi for power management and battery conservation. The display is a color e-paper display that not only looks great, but has the advantage of not needing power unless the display is updating. The Pi can be woken up to update the screen with new info when needed, but otherwise can spend its time asleep.

[Andrew] has a knack for friendly presentations of information with an underlying seriousness, as we saw with his friendly reminders about nasty product recalls.