Project Logs

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• The Last Update

  Guyrandy Jean-Gilles • 07/17/2024 at 01:43 • 0 comments

  Last update, I talked about choosing embedded Linux over a micro-controller to continue this project and how I would be playing with Buildroot to better understand that system. I've done that and WOW! (Almost) all the firmware functionality you've ever wanted has been pre-written for you to use for free... if you figure out how to configure the kernel. Getting a bare image of Buildroot is fairly straight forward, but I got lost in configuration hell trying to setup all the peripherals on the existing prototype.

  This made me take a step back and ask why I was down this path. The whole reason I had decided on embedded Linux vs a micro-controller was adding audio to the project would require more than userspace GPIO manipulation. After investigating other commercial e-readers, almost none of them have a 3.5mm audio jack, but instead rely on connection to a Bluetooth device. This is the route I went, and by the time you're reading this, the project description will be updated with exactly how this is done.

  This is the last update because the project does everything I want it to do at this point. It can read ebooks, play audiobooks, and sync with a remote server to download books. It is by no means polished, but it's the proof of concept I wanted to make when I began this idea.

• The Biggest Limitation to a Micro-controller Based E-reader

  Guyrandy Jean-Gilles • 04/17/2024 at 16:24 • 0 comments

  Last project log I discussed trying to reduce MuPDF to a size that could fit on memory reasonable for a micro-controller. Thankfully, the library's maintainers designed it so including or removing certain modules is as simple as changing a single configuration file. With the help of the maintainers, and their excellent documentation, I quickly realized that the size of the library is not due to the code itself but an artifact of the fonts included.

  Removing all the fonts dropped a test program (desktop, not embedded) from 40MB to 5MB with no other optimizations. Now, an e-reader with no fonts is not very useful. So I looked for small font families and slammed into a old problem. As of writing this, Unicode contains 149,878 characters. However, only 65,535 characters can be in a True Type font file. As a result, no single font family can represent all Unicode text an e-reader might encounter from an arbitrary book file.

  There are attempts to make a uniform typeface for all writing systems like Google Noto or GNU Unifont. But, for example, all the GNU Unifont OpenType fonts are ~12MB and the Google Noto fonts are ~10MB. Even ambitious projects like Joey Castillo's Babel use 2MB to represent Unicode's basic multilingual plane (65,520/149,878 characters as of version 15). EPDiy, an ESP32-based e-Reader project, requires editing the source to add or change fonts. Other generic micro-controller font libraries, like OpenFontRender for the Arduino ecosystem, MCUFont, or mcu-renderer require preprocessing the fonts on the host machine before programming the target device--almost always reducing the subset of characters that can be rendered.

  Simply put, fonts take a lot of storage. A micro-controller certainly can represent all the Unicode characters, but, given the low resource environment, it makes the most sense to limit the characters that can be rendered.

  I started down this path to decide if I should continue this project with a embedded Linux system or with a micro-controller system. Given the project's goal: democratizing e-books, supporting as many characters sets as possible is a priority. Thus embedded Linux is the better path to follow.

  My first step down this path is getting familiar with Buildroot, a tool that simplifies embedded Linux configuration. There are lots of examples for the Raspberry Pi boards, but I plan on eventually moving away from them to a custom board with a different chipset. There probably won't be any new hardware or software features for a while as I figure out Buildroot. Maybe I'll write up a getting started guide once I find a configuration I like. We'll see. Wish me luck.

• Bringing Up Version 0.5.1

  Guyrandy Jean-Gilles • 03/31/2024 at 20:19 • 0 comments

  I sent this version to fab in November of 2023, but didn't finish bringing up major board components until recently.

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• GUI Based Wifi Configuration

  Guyrandy Jean-Gilles • 02/29/2024 at 05:42 • 0 comments

  Software

  Despite the title, this is a hodge-podge update. The first concrete achievement I can boast is two new additions to the status bar: a clock and a Wifi menu.

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• User-Defined Book Servers

  Guyrandy Jean-Gilles • 01/31/2024 at 02:03 • 0 comments

  Happy New Year! I didn't work on this project much during the holidays and I realized I've had at least one project update a month since keeping this log. So I thought I'd put together what I've been working on. This will entirely be a software update and, as of writing this, the code is still in the development branch because it's not the cleanest implementation, but it's functional.
  

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• This eReader has a Touchscreen and Backlight!

  Guyrandy Jean-Gilles • 12/15/2023 at 00:05 • 0 comments

  The new CM4 and HAT PCBs for the GDEY042T81-FT02 are in and by and large they work. I still have to troubleshoot some hardware/firmware, but the project now has portable power, a touchscreen, and backlight.

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• PCB Layout for GDEY042T81-FT02

  Guyrandy Jean-Gilles • 11/24/2023 at 19:35 • 0 comments

  The latest PCB revision is on it's way to fabrication and there are lots of changes to note.

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• Bringing Up GDEY042T81-FT02

  Guyrandy Jean-Gilles • 11/09/2023 at 00:35 • 0 comments

  I'll skip to the happy ending. I can drive the display, the back light, and can read data from the touch screen, but achieving those milestones took much much longer than it should've. This update won't have much info on the actual e-reader project but is more a rant reflection on mistakes made while bringing up GDEY042T81-FT02 so I, and hopefully you, don't repeat them. Buckle up.

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• The First Attempt at Portable Power

  Guyrandy Jean-Gilles • 11/02/2023 at 13:19 • 0 comments

  The boards with lithium polymer charging are back and I've got mixed news: they mostly work. I ordered two (sponsored) designs from PCBWay: a dedicated lipo charger and a eReader carrier board with integrated lipo charging.

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• A Much Needed Refactor

  Guyrandy Jean-Gilles • 10/20/2023 at 04:49 • 0 comments

  I'm still waiting on the latest hardware revision to manufacture, so in the mean time I've been refactoring the code to be more modular and follow separation of concerns. The requirement that forced this task was writing firmware for the GDEY042T81-FT02 touchscreen sub-assemblies from Good Display. Previously, the project relied on the structure of code from Waveshare for the GDEW042T2. Moving away from Waveshare's structure to thin abstractions will make porting Good Display's vendor code to this project much easier.

  Here's an example. The project now has an abstraction layer for the e-paper aptly called "display.c/h" that contains the following function:

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