ESP-IDF-InkPlate/README.md

# ESP-IDF-InkPlate

A porting effort to the ESP-IDF framework for the e-Radionica InkPlate software that can be find [here](https://github.com/e-radionicacom/Inkplate-Arduino-library).

--> Work in progress. Not ready yet. <--

Beware that these classes are **not** re-entrant. That means that it is not possible to use them in a multi-thread context without proper mutual exclusion access control. 

This project is a working example. You can build it using PlatformIO. It will draw a square and a straight line on the device display.

## Modifications done to the Arduino Inkplate Source code

As you can expect, the ESP-IDF framework is quit different than the Arduino framework. The porting effort of the Inkplate source code done here is not just a transformation to make it runs, but also getting it inline with the available packages available with the ESP-IDF. Many aspects must be transformed in this regard. Here is a list of the changes being done:

### Global changes

- Give the overall source code a transformation to use what is called *modern C++*, alligned with C++17
- All .h files are renamed .hpp
- macro definitions (`#define`) are reduced to a minimum
- `enum class` are used everywhere possible
- source code filenames are all in lowercase

### SdCard

- The module is used only to initialize the ESP-IDF drivers (SPI and FAT filesystem are used). The card can then be accessed through the standard C++/C capabilities. All filenames located on the card must be prefixed with `/sdcard`.
  
### Image (.hpp, .cpp)

- the `drawXXXXFromWeb(WiFiClient *s, ...)` methods are no longer available.
- the `bool drawXXXXFromSd(SdFile *p, ...)` methods are renamed `bool drawXXXXFromFile(File *p, ...)`.
  
## ESP-IDF configuration specifics

An InkPlate application requires some functionalities to be properly set up within the ESP-IDF. The following elements have been done for this project and can be used as a reference for other projects:

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

  ```
  $ idf.py menuconfig
  ```

  The application will show a list of configuration aspects. 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**: If the application requires the usage of the micro SD card. This card must be formatted on a computer (Linux or Windows) with a FAT 32 partition. The InkPlate6Ctrl class requires this in its current configuration. 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`

- **Flash memory partitioning (optional)**: the file `partitions.csv` contains the table of partitions definition for the 4MB flash memory, required to support the largest applications size in an OTA context. The partitions OTA_0 and OTA_1 have been set to be 1.3MB in size. In the `platformio.ini` file, the line `board_build.partitions=...` is directing the use of these partitions configuration.