Espressif ESP32-S2 User Manual

Chapter 2. API Reference
WEBSOCKET_EVENT_CLOSED
The connection has been closed cleanly
WEBSOCKET_EVENT_MAX
enum esp_websocket_transport_t
Websocket Client transport.
Values:
WEBSOCKET_TRANSPORT_UNKNOWN = 0x0
Transport unknown
WEBSOCKET_TRANSPORT_OVER_TCP
Transport over tcp
WEBSOCKET_TRANSPORT_OVER_SSL
Transport over ssl
2.3.13 ESP Serial Slave Link
Overview
Espressif provides several chips that can work as slaves. These slave devices rely on some common buses, and have
their own communication protocols over those buses. The esp_serial_slave_link component is designed for the master
to communicate with ESP slave devices through those protocols over the bus drivers.
After an esp_serial_slave_link device is initialized properly, the application can use it to communicate with the ESP
slave devices conveniently.
Espressif Device protocols
For more details about Espressif device protocols, see the following documents.
ESP SPI Slave HD (Half Duplex) Mode Protocol
SPI Slave Capabilities of Espressif chips
ESP32 ESP32-S2 ESP32-C3
SPI Slave HD N Y (v2) Y (v2)
Tohost intr N N
Frhost intr 2 * 2 *
TX DMA Y Y
RX DMA Y Y
Shared registers 72 64
Introduction In the half duplex mode, the master has to use the protocol defined by the slave to communicate with
the slave. Each transaction may consist of the following phases (list by the order they should exist):
• Command: 8-bit, master to slave
This phase determines the rest phases of the transactions. See Supported Commands.
• Address: 8-bit, master to slave, optional
For some commands (WRBUF, RDBUF), this phase specifies the address of shared buffer to write
to/read from. For other commands with this phase, they are meaningless, but still have to exist in
the transaction.
• Dummy: 8-bit, floating, optional
This phase is the turn around time between the master and the slave on the bus, and also provides
enough time for the slave to prepare the data to send to master.
• Data: variable length, the direction is also determined by the command.
Espressif Systems 649
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Espressif ESP32-S2 Specifications

General

Brand	Espressif
Model	ESP32-S2
Category	Single board computers
Language	English