System Architecture: Linux Based Host

Below diagram depicts building blocks of Linux based ESP-Hosted solution.

1. ESP Host Software

This implements ESP-Hosted solution part that runs on Linux host. It mainly consists of following.

ESP Host driver implements following.

SDIO Host driver
This implements data path over SDIO interface. Communication protocol is explained in further section.
SPI Host driver
This implements data path over SPI interface. Communication protocol is explained in further section.
Virtual Serial interface driver
This implements virtual serial interface over SDIO/SPI interface. This virtual serial interface is used as a control interface to configure Wi-Fi of ESP peripheral
802.3 network interface
This registers two network interfaces with Linux kernel: ethsta0 and ethap0. This allows exchange of 802.3 frames between Linux kernel and ESP firmware.
HCI interface
This registers HCI interface with Linux kernel. This interface is implemented over SDIO/SPI.

This implements custom control commands that are based on protobuf.
These commands are used to control and configure Wi-Fi on ESP peripheral.
Control interface makes use of virtual serial interface provided by ESP Host driver.
There are 2 flavors of control interface implementation:
- C based implementation
- Python based implementation - It uses C based implementation using ctypes package.
API's are described in subsequent section
Control path design and implemetation details explained in Control Path documentation