mirror of
https://github.com/espressif/esp-idf.git
synced 2025-10-30 20:51:41 +00:00
191 lines
7.0 KiB
ReStructuredText
191 lines
7.0 KiB
ReStructuredText
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.
|
|
|
|
.. toctree::
|
|
:maxdepth: 1
|
|
|
|
:SOC_SDIO_SLAVE_SUPPORTED: esp_sdio_slave_protocol
|
|
esp_spi_slave_protocol
|
|
|
|
Terminology
|
|
-----------
|
|
|
|
- ESSL: Abbreviation for ESP Serial Slave Link, the component described by this document.
|
|
|
|
- Master: The device running the `esp_serial_slave_link` component.
|
|
|
|
- ESSL device: a virtual device on the master associated with an ESP slave device. The device
|
|
context has the knowledge of the slave protocol above the bus, relying on some bus drivers to
|
|
communicate with the slave.
|
|
|
|
- ESSL device handle: a handle to ESSL device context containing the configuration, status and
|
|
data required by the ESSL component. The context stores the driver configurations,
|
|
communication state, data shared by master and slave, etc.
|
|
|
|
The context should be initialized before it is used, and get deinitialized if not used any more. The
|
|
master application operates on the ESSL device through this handle.
|
|
|
|
- ESP slave: the slave device connected to the bus, which ESSL component is designed to
|
|
communicate with.
|
|
|
|
- Bus: The bus over which the master and the slave communicate with each other.
|
|
|
|
- Slave protocol: The special communication protocol specified by Espressif HW/SW over the bus.
|
|
|
|
- TX buffer num: a counter, which is on the slave and can be read by the master, indicates the
|
|
accumulated buffer numbers that the slave has loaded to the hardware to receive data from the
|
|
master.
|
|
|
|
- RX data size: a counter, which is on the slave and can be read by the master, indicates the
|
|
accumulated data size that the slave has loaded to the hardware to send to the master.
|
|
|
|
Services provided by ESP slave
|
|
------------------------------
|
|
|
|
There are some common services provided by the Espressif slaves:
|
|
|
|
1. Tohost Interrupts: The slave can inform the master about certain events by the interrupt line. (optional)
|
|
|
|
2. Frhost Interrupts: The master can inform the slave about certain events.
|
|
|
|
3. Tx FIFO (master to slave): the slave can send data in stream to the master. The SDIO slave can
|
|
also indicate it has new data to send to master by the interrupt line.
|
|
|
|
The slave updates the TX buffer num to inform the master how much data it can receive, and the
|
|
master then read the TX buffer num, and take off the used buffer number to know how many buffers are remaining.
|
|
|
|
4. Rx FIFO (slave to master): the slave can receive data from the master in units of receiving
|
|
buffers.
|
|
|
|
The slave updates the RX data size to inform the master how much data it has prepared to
|
|
send, and then the master read the data size, and take off the data length it has already received to know how many
|
|
data is remaining.
|
|
|
|
5. Shared registers: the master can read some part of the registers on the slave, and also write
|
|
these registers to let the slave read.
|
|
|
|
.. only:: SOC_SDIO_SLAVE_SUPPORTED
|
|
|
|
The services provided by the slave depends on the slave's model. See :ref:`esp_sdio_slave_caps` and :ref:`esp_spi_slave_caps` for more details.
|
|
|
|
.. only:: not SOC_SDIO_SLAVE_SUPPORTED
|
|
|
|
The services provided by the slave depends on the slave's model. See :ref:`esp_spi_slave_caps` for more details.
|
|
|
|
|
|
Initialization of ESP Serial Slave Link
|
|
---------------------------------------
|
|
|
|
.. _essl_sdio_slave_init:
|
|
|
|
ESP SDIO Slave
|
|
^^^^^^^^^^^^^^
|
|
|
|
The ESP SDIO slave link (ESSL SDIO) devices relies on the sdmmc component. It includes the usage
|
|
of communicating with ESP SDIO Slave device via SDSPI feature. The ESSL device should be
|
|
initialized as below:
|
|
|
|
1. Initialize a sdmmc card (see :doc:` Document of SDMMC driver </api-reference/storage/sdmmc>`)
|
|
structure.
|
|
|
|
2. Call :cpp:func:`sdmmc_card_init` to initialize the card.
|
|
|
|
3. Initialize the ESSL device with :cpp:type:`essl_sdio_config_t`. The `card` member should be
|
|
the :cpp:type:`sdmmc_card_t` got in step 2, and the `recv_buffer_size` member should be filled
|
|
correctly according to pre-negotiated value.
|
|
|
|
4. Call :cpp:func:`essl_init` to do initialization of the SDIO part.
|
|
|
|
5. Call :cpp:func:`essl_wait_for_ready` to wait for the slave to be ready.
|
|
|
|
ESP SPI Slave
|
|
^^^^^^^^^^^^^
|
|
|
|
.. note::
|
|
If you are communicating with the ESP SDIO Slave device through SPI interface, you should use
|
|
the :ref:`SDIO interface <essl_sdio_slave_init>` 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 :cpp:func:`essl_get_intr_ena` to know which events will trigger the interrupts to the master.
|
|
|
|
2. Call :cpp:func:`essl_set_intr_ena` to set the events that will trigger interrupts to the master.
|
|
|
|
3. Call :cpp:func:`essl_wait_int` to wait until interrupt from the slave, or timeout.
|
|
|
|
4. When interrupt is triggered, call :cpp:func:`essl_get_intr` to know which events are active,
|
|
and call :cpp:func:`essl_clear_intr` to clear them.
|
|
|
|
Frhost Interrupts
|
|
^^^^^^^^^^^^^^^^^
|
|
|
|
1. Call :cpp:func:`essl_send_slave_intr` to trigger general purpose interrupt of the slave.
|
|
|
|
TX FIFO
|
|
^^^^^^^
|
|
|
|
1. Call :cpp:func:`essl_get_tx_buffer_num` to know how many buffers the slave has prepared to
|
|
receive data 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 :cpp:func:`essl_send_paket` to send data to the slave.
|
|
|
|
RX FIFO
|
|
^^^^^^^
|
|
|
|
1. Call :cpp:func:`essl_get_rx_data_size` to know how many data the slave has prepared to send to
|
|
the master. 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 :cpp:func:`essl_get_packet` to receive data from the slave.
|
|
|
|
Reset counters (Optional)
|
|
^^^^^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
Call :cpp:func:`essl_reset_cnt` to reset the internal counter if you find the slave has reset its
|
|
counter.
|
|
|
|
|
|
Application Example
|
|
-------------------
|
|
|
|
The example below shows how ESP32 SDIO host and slave communicate with each other. The host use the ESSL SDIO.
|
|
|
|
:example:`peripherals/sdio`.
|
|
|
|
Please refer to the specific example README.md for details.
|
|
|
|
API Reference
|
|
-------------
|
|
|
|
.. include-build-file:: inc/essl.inc
|
|
.. include-build-file:: inc/essl_sdio.inc
|
|
.. include-build-file:: inc/essl_spi.inc
|