A project log for Low Power ESP32 Handheld

Pocket sized ESP32 display board with 300µW Always On Display

Max.KMax.K 12/24/2019 at 11:150 Comments

Earlier this year Panic, the software studio behind the Untitled Goose Game, introduced their Playdate console. It's a retro handheld device with a monochrome display and a crank as an input device: I really liked the simplicity of it and decided to make something similar. It was also a chance to improve on my 2016 Chronio Smartwatch concept which features a similar display but only an ATmega328.

The display board is using the same 2.7" Sharp memory display as the Playdate. These displays only consume a few µAs and because of their in-pixel-memory they don't need constant refreshing. They are also readably under direct sunlight with no need for backlighting.
As its brains the board is using an ESP32. The dual core chip has enough processing power to drive the display while also featuring WiFi and Bluetooth. And it has a ULP co-processor for low power applications. I decided to include a small 5-way joystick and two buttons to enable simple games. As I wanted the device to work as a bare PCB without 3D-printed parts, a mechanical crank was out of the question.

The size of the needed PCB is defined by the display and buttons. With the display on the front, the ESP32 and all other components fit nicely on the back of the device. A milled slot enables the display flex cable to go through the PCB and into its connector.

I was able to reuse some of the parts and circuits from my ESP32 robot but it was challenging to keep the power consumption to a minimum. More on that in a separate project log.