turgu1 / chess-inkplate

A Simple Chess Player for the InkPlate devices

Chess-InkPlate A Simple Chess Player for the InkPlate devices

Last news

(Updated 2021.03.04)

Update to version 1.2

• Recompiled to integrate ESP-IDF-Inkplate library v0.9.4
• Adjustments for the ESP-IDF v4.2 framework
• Support for the 6-buttons extended board in new specific releases
• bld_all.sh script to automatically build all releases zip files

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This is a simple chess application for the InkPlate devices. It is based on the chess engine developed by Sergey Urusov as an Arduino project. I edited and ported the engine for inclusion under the ESP-IDF framework. You can find Sergey's original code here.

I've used the framework developped for the EPub-InkPlate app. It was extracted from the specifics of the EPub reader and adapted for the Chess-InkPlate app. These are the steps taken to build it:

• Extraction of the Chess Engine portion required from the Arduino code
• Transformation of the Engine in C++
• Engine integration in my own InkPlate framework
• Integration of Chess fonts
• Graphical Chess board display
• Interaction with the chess board
• Integration with the chess engine
• PGN notation
• Menu for main actions
• Menu for chess font selection
• Menu for pawn promotion
• Pawn promotion integration
• Current game save and load on deep sleep
• User Manual
• Installation manual
• Deep Sleep management

Potential features for v2.0:

• Access to external chess engines
• Book moves for beginning of games
• Games database display and interaction
• Training (puzzle)
• Play against other users through internet chess servers
• Played games save/load/replay

Runtime environment

The Chess-InkPlate application requires that a micro-SD Card be present in the device. This micro-SD Card must be pre-formatted with a FAT32 partition. One folder must be present in the partition: fonts. You must put the base fonts in the fonts folder.

The SDCard folder under GitHub reflects what the micro-SD Card should look like.

Fonts cleanup

All (non-chess) fonts have been subsetted to Latin-1 plus some usual characters. The fonts/orig folder in the GitHub project contains all original fonts that are processed using the script fonts/subsetter.sh. This script uses the Python pyftsubset tool that is part of the fontTools package. To install the tool, you need to execute the following command:

$ pip install fonttools brotli zopfli

The script takes all font from the orig folder and generate the new subset fonts in subset-latin1/otf folder. The following commands must be executed:

$ cd fonts
$ ./subsetter.sh

After that, all fonts in the subset-latin1/otf and chess folder must be copied back in the SDCard/fonts folder.

Development environment

Visual Studio Code is the code editor I'm using. The PlatformIO extension is used to manage application configuration for both Linux and the ESP32.

All source code is located in various folders:

• Source code used by both Linux and InkPlate is located in the include and src folders
• Source code in support of Linux only is located in the lib_linux folder
• Source code in support of the InkPlate device (ESP32) only are located in the lib_esp32 folder
• The FreeType library for ESP32 is in folder lib_freetype

The file platformio.ini contains the configuration options required to compile both Linux and InkPlate applications.

Note that source code located in folders old and test is not used. It will be deleted from the project when the application development will be completed.

Dependencies

The following are the libraries currently in use by the application:

• GTK+3 (Only for the Linux version) The development headers must be installed. This can be done with the following command (on Linux Mint):

  $ sudo apt-get install build-essential libgtk-3-dev

The following is imported C header and source files, that implement some algorithms:

• FreeType (Parse, decode, and rasterize characters from TrueType fonts) A version of the library has been loaded in folder freetype-2.10.4/ and compiled with specific options for the ESP32. See sub-section FreeType library compilation for ESP32 below for further explanations.

FreeType library compilation for ESP32

The FreeType library is using a complex makefile structure to simplify (!) the compilation process. Here are the steps used to get a library suitable for integration in the Chess-InkPlate ESP32 application. As this process is already done, there is no need to run it again, unless a new version of the library is required or some changes to the modules selection are done.

1. The folder named lib_freetype is created to receive the library and its dependencies at install time:

   $ mkdir lib_freetype

2. The ESP-IDF SDK must be installed in the main user folder. Usually, it is in folder ~/esp. The following location documents the installation procedure: https://docs.espressif.com/projects/esp-idf/en/latest/esp32/get-started/index.html . Look at Steps 1 to 4 (Setting Up Development Environment). This is important as the configuration setup below will access ESP32 related compilation tools.

3. The files freetype-2.10.4/modules.cfg and freetype-2.10.4/include/freetype/config/ftoption.h are modified to only keep the capabilities required to support TrueType and OpenType fonts. The original files have been saved in *.orig files.

4. A file named freetype-2.10.4/myconf.sh is created to simplify the configuration of the makefile structure. The --prefix option may require some modification to take into account the location where the Chess-InkPlate source code has been put. The --prefix must point to the lib_freetype folder.

5. The following commands are executed:

   $ cd freetype-2.10.4
   $ bash myconf.sh
   $ make
   $ make install

   This will have created several files in the folder lib_freetype.

6. Edit file named lib_freetype/lib/pkgconfig/freetype2.pc and remove the entire line that contains harfbuzz reference.

7. Voilà...

ESP-IDF configuration specifics

The Chess-InkPlate application requires some functionalities to be properly set up within the ESP-IDF. To do so, some parameters located in the sdkconfig file must be set accordingly. This must be done using the menuconfig application that is part of the ESP-IDF.

The ESP-IDF SDK must be installed in the main user folder. Usually, it is in folder ~/esp. The following location documents the installation procedure: https://docs.espressif.com/projects/esp-idf/en/latest/esp32/get-started/index.html . Look at Steps 1 to 4 (Setting Up Development Environment).

The following command will launch the application (the current folder must be the main folder of Chess-InkPlate):

$ idf.py menuconfig

The application will show a list of configuration aspects.

The following elements have been done (No need to do it again):

• PSRAM memory management: The PSRAM is an extension to the ESP32 memory that offers 4MB+4MB of additional RAM. The first 4MB is readily available to integrate into the dynamic memory allocation of the ESP-IDF SDK. To configure PSRAM:

  • Select Component Config > ESP32-Specific > Support for external, SPI-Connected RAM
  • Select SPI RAM config > Initialize SPI RAM during startup
  • Select Run memory test on SPI RAM Initialization
  • Select Enable workaround for bug in SPI RAM cache for Rev 1 ESP32s
  • Select SPI RAM access method > Make RAM allocatable using malloc() as well

  Leave the other options as they are.

• ESP32 processor speed: The processor must be run at 240MHz. The following line in platformio.ini request this speed:

  board_build.f_cpu = 240000000L
  

  You can also select the speed in the sdkconfig file:

  • Select Component config > ESP32-Specific > CPU frequency > 240 Mhz

• FAT Filesystem Support: The application requires the usage of the micro SD card. This card must be formatted on a computer (Linux or Windows) with a FAT32 partition (maybe not required as this is the default format of brand new cards). The following parameters must be adjusted in sdkconfig:

  • Select Component config > FAT Filesystem support > Max Long filename length > 255
  • Select Number of simultaneously open files protected by lock function > 5
  • Select Prefer external RAM when allocating FATFS buffer
  • Depending on the language to be used (My own choice is Latin-1 (CP850)), select the appropriate Code Page for filenames. Select Component config > FAT Filesystem support > OEM Code Page.... DO NOT use Dynamic as it will add ~480KB to the application!!
  • Also select Component config > FAT Filesystem support > API character encoding > ... UTF-8 ...

• HTTP Server: (This is a feature to be made available in version 2.0) The application is supplying a Web server (through the use of HTTP) to the user to modify the list of games present on the SDCard. The following parameters must be adjusted:

  • Select Component config > HTTP Server > Max HTTP Request Header Length > 1024
  • Select Component config > HTTP Server > Max HTTP URI Length > 1024

The following is not configured through menuconfig:

• Flash memory partitioning: the file partitions.csv contains the table of partitions required to support the application in the 4MB flash memory. The factory partition has been set to be ~2.4MB in size (OTA is not possible as the application is too large to accomodate this feature; the OTA related partitions have been commented out...). In the platformio.ini file, the line board_build.partitions=... is directing the use of these partitions configuration.