Guition ESP32-2432S028R
2.8"
Guition-branded 2.8-inch Cheap Yellow Display with ILI9341 controller and resistive touch.
An Ampernomics project
Designed to turn dynamic tariffs into simple everyday decisions.
Greenlight is a small open-source display for Octopus Agile prices.
Instead of checking apps and price graphs throughout the day, Greenlight sits in your kitchen or utility room and shows when electricity is currently cheap or expensive — along with when the next cheaper period begins.
Why Greenlight exists
Pricing signals shouldn't be hidden inside an app.
Many households can save money simply by moving onto a time-of-use tariff like Octopus Agile — even without changing behaviour.
But once you are on a dynamic tariff, timing starts to matter.
The problem is that pricing signals are usually buried inside apps and dashboards. Most people are not going to repeatedly check half-hourly prices before deciding whether to run the dishwasher or tumble dryer.
Greenlight turns those pricing signals into something ambient and visible:
Red
Electricity is expensive right now.
Green
Electricity is cheap right now.
Countdown
When the next cheaper period begins.
The goal is not obsessive optimisation. Just gentle behavioural nudges at the point decisions are made.
Small shifts add up
On Octopus Agile, prices vary throughout the day.
Typical peak vs off-peak differences
- › Dishwasher cycle: ~10–25p difference
- › Washing machine: ~5–15p difference
- › Tumble dryer: often significantly more
Greenlight makes those pricing changes visible without requiring constant attention.
Examples vary depending on appliance energy use and daily Agile pricing.
Open source
Built on inexpensive hardware. Fully open.
- ● ESP32 based
- ● Open source
- ● Designed for Cheap Yellow Display
- ● Built using ESP-IDF + LVGL
Supported hardware
Greenlight runs on these ESP32 boards.
ESP32-2432S028 clone
2.8"
2.8-inch CYD variant with ST7789 controller available from Amazon UK.
ESP32-32E
3.2"
3.2-inch ESP32-32E board, larger display with resistive touch.
AliExpress listings frequently reuse the same model numbers across slightly different hardware. Match the LCD controller (ILI9341 vs ST7789) before flashing.
Flash your device
Already have compatible hardware?
Flash Greenlight directly from your browser using Web Serial. No drivers, no toolchain — just plug the board into a USB data cable and click install.
- Connect the device with a USB data cable (not just charging).
- Open this page in Chrome or Edge on a desktop computer.
- Select your board variant below.
- Click Install Greenlight and pick the serial device.
- Wait for the flash to complete, then unplug and power on.
Current builds are still aimed primarily at hobbyists/tinkerers. You may occasionally need to update firmware manually while the project evolves.
Prebuilt devices
Interested in a prebuilt Greenlight?
A few people have asked about prebuilt units, so I’m exploring putting together a small batch with pre-flashed firmware, a 3D printed case, and wall or shelf mounting options.
This is currently an interest list only — no commitment or payment required.
Philosophy
Greenlight is intentionally simple.
It is not trying to be:
- — a smart home dashboard
- — a full energy monitor
- — a complex optimisation tool
The goal is simply to make dynamic electricity pricing visible enough that small behavioural changes happen naturally over time.