Espressif ESP32-S2 Programming Manual page 664

Chapter 2. API Reference
4. Call essl_init() to do initialization of the SDIO part.
5. Call essl_wait_for_ready()
ESP SPI Slave
Note: If you are communicating with the ESP SDIO Slave device through SPI interface, you should use the
interface instead.
Hasn't been supported yet.
APIs
After the initialization process above is performed, you can call the APIs below to make use of the services provided
by the slave:
Tohost Interrupts (optional)
1. Call essl_get_intr_ena()
2. Call essl_set_intr_ena()
3. Call essl_wait_int()
4. When interrupt is triggered, call
essl_clear_intr()
Frhost Interrupts
1. Call essl_send_slave_intr()
TX FIFO
1. Call essl_get_tx_buffer_num()
from the master. This is optional. The master will poll tx_buffer_num when it try to send packets to the slave,
until the slave has enough buffer or timeout.
2. Call essl_send_paket() to send data to the slave.
RX FIFO
1. Call essl_get_rx_data_size()
This is optional. When the master tries to receive data from the slave, it will update the rx_data_size for once,
if the current rx_data_size is shorter than the buffer size the master prepared to receive. And it may poll the
rx_data_size if the rx_dat_size keeps 0, until timeout.
2. Call essl_get_packet()
Reset counters (Optional)
its counter.
Application Example
The example below shows how ESP32-S2 SDIO host and slave communicate with each other. The host use the ESSL
SDIO.
peripherals/sdio.
Please refer to the specific example README.md for details.
Espressif Systems
to wait for the slave to be ready.
to know which events will trigger the interrupts to the master.
to set the events that will trigger interrupts to the master.
to wait until interrupt from the slave, or timeout.
essl_get_intr()
to clear them.
to trigger general purpose interrupt of the slave.
to know how many buffers the slave has prepared to receive data
to know how many data the slave has prepared to send to the master.
to receive data from the slave.
Call essl_reset_cnt()
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to know which events are active, and call
to reset the internal counter if you find the slave has reset
SDIO
Release v4.4