espressif_idf-extra-components/esp_serial_slave_link/README.md

Espressif Serial Slave Link (ESSL) component

This component used to reside in esp-idf project as its component.

It's used on the HOST, to communicate with ESP chips as SLAVE via SDIO/SPI slave HD mode.

The port layer (essl_sdio.c/essl_spi.c) are currently only written to run on ESP chips in master mode, but you may also modify them to work on more platforms.

See more documentation: https://docs.espressif.com/projects/esp-idf/en/latest/esp32/api-reference/protocols/esp_serial_slave_link.html