esp_wifi_remote

The esp_wifi_remote component provides transparent WiFi connectivity for ESP chipsets through external hardware, maintaining full esp_wifi API compatibility.

Use Cases

Non-WiFi ESP Chips: Enables WiFi functionality on ESP32-P4, ESP32-H2 and other WiFi-less chipsets by routing esp_wifi calls to external WiFi hardware.

Additional WiFi Interface: On WiFi-capable ESP32 chips, provides dual WiFi interfaces - local esp_wifi and remote esp_wifi_remote for applications requiring multiple wireless connections.

To employ this component, a slave device -- capable of WiFi connectivity -- must be connected to your target device in a specified manner, as defined by the transport layer of esp_hosted.

Functionally, esp_wifi_remote wraps the public API of esp_wifi, offering a set of function call namespaces prefixed with esp_wifi_remote. These calls are translated into Remote Procedure Calls (RPC) to another target device (referred to as the "slave" device), which then executes the appropriate esp_wifi APIs.

Notably, esp_wifi_remote heavily relies on a specific version of the esp_wifi component. Consequently, the majority of its headers, sources, and configuration files are pre-generated based on the actual version of esp_wifi.

It's important to highlight that esp_wifi_remote does not directly implement the RPC calls; rather, it relies on dependencies for this functionality.

Terminology

• Backend Solution: Communication layer handling transport of WiFi commands, events, and data between host and slave devices (e.g., esp-hosted, eppp, AT-based implementations)
• Host-side: Device running your application code (e.g., ESP32-P4, ESP32-H2, or ESP32 with WiFi)
• Slave-side: WiFi-capable device providing actual WiFi hardware and functionality

Backend Solutions

esp_wifi_remote supports multiple backend solutions for RPC communication:

• esp_hosted (recommended): Plain text channels for WiFi API calls/events and Ethernet frames for data. Best performance and maturity.
• wifi_remote_over_eppp: SSL/TLS encrypted connection with PPP link. Suitable when encryption is required.
• wifi_remote_over_at: AT commands via esp-modem. Limited functionality but uses standard protocols.

Performance Comparison

WiFi Configuration

Configure remote WiFi identically to local WiFi via Kconfig. Options use WIFI_RMT_ prefix instead of ESP_WIFI_:

CONFIG_ESP_WIFI_TX_BA_WIN → CONFIG_WIFI_RMT_TX_BA_WIN
CONFIG_ESP_WIFI_AMPDU_RX_ENABLED → CONFIG_WIFI_RMT_AMPDU_RX_ENABLED

Note: Some configuration options are compile-time only. Manual slave-side configuration and rebuild required for consistency.

Dependencies on esp_wifi

Public API needs to correspond exactly to the esp_wifi API. Some of the internal types depend on the actual wifi target, as well as some default configuration values. Therefore it's easier to maintain consistency between this component and the exact version of esp_wifi automatically in CI:

• We extract function prototypes from esp_wifi.h and use them to generate esp_wifi_remote function declarations.
• We process the local esp_wifi_types_native.h and replace CONFIG_IDF_TARGET to CONFIG_SLAVE_IDF_TARGET and CONFIG_SOC_WIFI_... to CONFIG_SLAVE_....
• Similarly we process esp_wifi's Kconfig, so the dependencies are on the slave target and slave SOC capabilities.

Please check the README.md for more details on the generation step and testing consistency.