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An Improved WiFi Connected E-Ink Display
Monday, 13 June 2016 16:00

[David] created a great looking e-ink WiFi display project that works a little like a network-connected picture frame with a few improvements over other similar projects. With the help of an ESP8266 it boots up, grabs an 800×600 image over the network, updates the screen, then goes back to sleep. Thanks to some reverse engineering, he was able to make his own firmware for the onboard controller to handle the low-level driving of the display. Since e-ink displays require no power to hold an image and the rest of the unit spends most of the time either asleep or off, power use is extremely low. [David] hopes to go months without needing to recharge the internal lithium-polymer battery.

Lithium-polymer charger (top left); Single-cell lithium-polymer battery (center); pullups and power cutoff for nonessential electronics (green board, lower right); ESP866 (lower left).

We previously featured another WiFi-connected e-ink display project that was in fact also the inspiration for this version. [David] uses a 4.3″ 800×600 GDE043A e-ink display and wrote his own firmware for the STM32F103ZE ARM CortexM3 SoC used as a display controller, a process that required some reverse engineering but was aided by the manufacturer providing a closed-source driver for him to use. [David] writes that some reverse-engineering work for this display had already been done, but he had such a hard time getting a clear understanding from it that he reverse engineered the firmware anyway and used the documents mainly for validation and guidance.

As a result, [David] was able to make use of the low-level driver electronics already present on the board instead of having to make and interface his own. E-ink displays have some unusual driving requirements which include generating relatively high positive and negative voltages, and rapidly switching them when updating the display. Taking advantage of the board’s existing low-level driver electronics was a big benefit.

eink_apThe ESP8266 rounds out the project by taking care of periodically booting things up, connecting to the wireless network and downloading an image, feeding the image data to the STM32 to update the display, then disconnecting power from all non-essential electronics and going back to sleep. We especially like how the unit automatically creates a WiFi access point to allow easy (re)configuring.

There’s one more nice touch. [David] goes the extra mile with server software (in the form of PHP scripts) to design screens for the display with data like weather forecasts, stock prices, and exchange rates. Check it out in the project’s github repository.

Filed under: ARM, wireless hacks