esp-idf/components/driver/include/driver/spi_slave.h

// Copyright 2010-2017 Espressif Systems (Shanghai) PTE LTD
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at

//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.


#ifndef _DRIVER_SPI_SLAVE_H_
#define _DRIVER_SPI_SLAVE_H_

#include "esp_err.h"
#include "freertos/FreeRTOS.h"
#include "freertos/semphr.h"
#include "driver/spi_common.h"


#ifdef __cplusplus
extern "C"
{
#endif


#define SPI_SLAVE_TXBIT_LSBFIRST          (1<<0)  ///< Transmit command/address/data LSB first instead of the default MSB first
#define SPI_SLAVE_RXBIT_LSBFIRST          (1<<1)  ///< Receive data LSB first instead of the default MSB first
#define SPI_SLAVE_BIT_LSBFIRST            (SPI_TXBIT_LSBFIRST|SPI_RXBIT_LSBFIRST); ///< Transmit and receive LSB first


typedef struct spi_slave_transaction_t spi_slave_transaction_t;
typedef void(*slave_transaction_cb_t)(spi_slave_transaction_t *trans);

/**
 * @brief This is a configuration for a SPI host acting as a slave device.
 */
typedef struct {
    int spics_io_num;               ///< CS GPIO pin for this device
    uint32_t flags;                 ///< Bitwise OR of SPI_SLAVE_* flags
    int queue_size;                 ///< Transaction queue size. This sets how many transactions can be 'in the air' (queued using spi_slave_queue_trans but not yet finished using spi_slave_get_trans_result) at the same time
    uint8_t mode;                   ///< SPI mode (0-3)
    slave_transaction_cb_t post_setup_cb; ///< Callback called after the SPI registers are loaded with new data
    slave_transaction_cb_t post_trans_cb; ///< Callback called after a transaction is done
} spi_slave_interface_config_t;

/**
 * This structure describes one SPI transaction
 */
struct spi_slave_transaction_t {
    size_t length;                  ///< Total data length, in bits
    const void *tx_buffer;          ///< Pointer to transmit buffer, or NULL for no MOSI phase
    void *rx_buffer;                ///< Pointer to receive buffer, or NULL for no MISO phase
    void *user;                     ///< User-defined variable. Can be used to store eg transaction ID.
};

/**
 * @brief Initialize a SPI bus
 *
 * @warning For now, only supports HSPI and VSPI.
 *
 * @param host SPI peripheral to use as a SPI slave interface
 * @param bus_config Pointer to a spi_bus_config_t struct specifying how the host should be initialized
 * @param slave_config Pointer to a spi_slave_interface_config_t struct specifying the details for the slave interface
 * @param dma_chan Either 1 or 2. A SPI bus used by this driver must have a DMA channel associated with
 *                 it. The SPI hardware has two DMA channels to share. This parameter indicates which
 *                 one to use.
 * @return 
 *         - ESP_ERR_INVALID_ARG   if configuration is invalid
 *         - ESP_ERR_INVALID_STATE if host already is in use
 *         - ESP_ERR_NO_MEM        if out of memory
 *         - ESP_OK                on success
 */
esp_err_t spi_slave_initialize(spi_host_device_t host, const spi_bus_config_t *bus_config, const spi_slave_interface_config_t *slave_config, int dma_chan);

/**
 * @brief Free a SPI bus claimed as a SPI slave interface
 *
 * @param host SPI peripheral to free
 * @return 
 *         - ESP_ERR_INVALID_ARG   if parameter is invalid
 *         - ESP_ERR_INVALID_STATE if not all devices on the bus are freed
 *         - ESP_OK                on success
 */
esp_err_t spi_slave_free(spi_host_device_t host);


/**
 * @brief Queue a SPI transaction for execution
 *
 * This will queue a transaction for the master to pick it up. If the queue (specified in ``spi_slave_initialize``)
 * is not full, this function will return directly; the actual transaction will be done if there aren't any
 * unhandled transactions before it and the master initiates a SPI transaction by pulling down CS and sending out
 * clock signals.
 *
 * @param host SPI peripheral that is acting as a slave
 * @param trans_desc Description of transaction to execute. Not const because we may want to write status back
 *                   into the transaction description.
 * @param ticks_to_wait Ticks to wait until there's room in the queue; use portMAX_DELAY to
 *                      never time out.
 * @return 
 *         - ESP_ERR_INVALID_ARG   if parameter is invalid
 *         - ESP_OK                on success
 */
esp_err_t spi_slave_queue_trans(spi_host_device_t host, const spi_slave_transaction_t *trans_desc, TickType_t ticks_to_wait);


/**
 * @brief Get the result of a SPI transaction queued earlier
 *
 * This routine will wait until a transaction to the given device (queued earlier with 
 * spi_slave_queue_trans) has succesfully completed. It will then return the description of the
 * completed transaction so software can inspect the result and e.g. free the memory or 
 * re-use the buffers.
 *
 * @param host SPI peripheral to that is acting as a slave
 * @param trans_desc Pointer to variable able to contain a pointer to the description of the 
 *                   transaction that is executed
 * @param ticks_to_wait Ticks to wait until there's a returned item; use portMAX_DELAY to never time
 *                      out.
 * @return 
 *         - ESP_ERR_INVALID_ARG   if parameter is invalid
 *         - ESP_OK                on success
 */
esp_err_t spi_slave_get_trans_result(spi_host_device_t host, spi_slave_transaction_t **trans_desc, TickType_t ticks_to_wait);


/**
 * @brief Do a SPI transaction
 *
 * Essentially does the same as spi_slave_queue_trans followed by spi_slave_get_trans_result. Do
 * not use this when there is still a transaction queued that hasn't been finalized 
 * using spi_slave_get_trans_result.
 *
 * @param host SPI peripheral to that is acting as a slave
 * @param trans_desc Pointer to variable able to contain a pointer to the description of the 
 *                   transaction that is executed. Not const because we may want to write status back
 *                   into the transaction description.
 * @param ticks_to_wait Ticks to wait until there's a returned item; use portMAX_DELAY to never time
 *                      out.
 * @return 
 *         - ESP_ERR_INVALID_ARG   if parameter is invalid
 *         - ESP_OK                on success
 */
esp_err_t spi_slave_transmit(spi_host_device_t host, spi_slave_transaction_t *trans_desc, TickType_t ticks_to_wait);


#ifdef __cplusplus
}
#endif

#endif