SPI.h

/* mbed Microcontroller Library
 * Copyright (c) 2006-2019 ARM Limited
 * SPDX-License-Identifier: Apache-2.0
 *
 * 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 MBED_SPI_H
#define MBED_SPI_H

#include "platform/platform.h"

#if DEVICE_SPI || defined(DOXYGEN_ONLY)

#include "platform/PlatformMutex.h"
#include "hal/spi_api.h"
#include "drivers/DigitalOut.h"
#include "platform/SingletonPtr.h"
#include "platform/NonCopyable.h"

#if defined MBED_CONF_DRIVERS_SPI_COUNT_MAX && DEVICE_SPI_COUNT > MBED_CONF_DRIVERS_SPI_COUNT_MAX
#define SPI_PERIPHERALS_USED MBED_CONF_DRIVERS_SPI_COUNT_MAX
#elif defined DEVICE_SPI_COUNT
#define SPI_PERIPHERALS_USED DEVICE_SPI_COUNT
#else
/* Backwards compatibility with HALs not providing DEVICE_SPI_COUNT */
#define SPI_PERIPHERALS_USED 1
#endif

#if DEVICE_SPI_ASYNCH
#include "platform/CThunk.h"
#include "hal/dma_api.h"
#include "platform/CircularBuffer.h"
#include "platform/Callback.h"
#include "platform/Transaction.h"
#endif

namespace mbed {
/**
 * \addtogroup drivers_SPI SPI class
 * \ingroup drivers-public-api-spi
 * @{
 */

struct use_gpio_ssel_t { };
const use_gpio_ssel_t use_gpio_ssel;

/** A SPI Master, used for communicating with SPI slave devices.
 *
 * The default format is set to 8-bits, mode 0, and a clock frequency of 1MHz.
 *
 * Most SPI devices will also require Chip Select and Reset signals. These
 * can be controlled using DigitalOut pins.
 *
 * @note Synchronization level: Thread safe
 *
 * Example of how to send a byte to a SPI slave and record the response:
 * @code
 * #include "mbed.h"
 *
 * SPI device(SPI_MOSI, SPI_MISO, SPI_SCLK)
 *
 * DigitalOut chip_select(SPI_CS);
 *
 * int main() {
 *     device.lock();
 *     chip_select = 0;
 *
 *     int response = device.write(0xFF);
 *
 *     chip_select = 1;
 *     device.unlock();
 * }
 * @endcode
 *
 * Example using hardware Chip Select line:
 * @code
 * #include "mbed.h"
 *
 * SPI device(SPI_MOSI, SPI_MISO, SPI_SCLK, SPI_CS)
 *
 * int main() {
 *     device.lock();
 *     int response = device.write(0xFF);
 *     device.unlock();
 * }
 * @endcode
 */
class SPI : private NonCopyable<SPI> {

public:

    /** Create a SPI master connected to the specified pins.
     *
     *  @note This constructor passes the SSEL pin selection to the target HAL.
     *  Not all targets support SSEL, so this cannot be relied on in portable code.
     *  Portable code should use the alternative constructor that uses GPIO
     *  for SSEL.
     *
     *  @note You can specify mosi or miso as NC if not used.
     *
     *  @param mosi SPI Master Out, Slave In pin.
     *  @param miso SPI Master In, Slave Out pin.
     *  @param sclk SPI Clock pin.
     *  @param ssel SPI Chip Select pin.
     */
    SPI(PinName mosi, PinName miso, PinName sclk, PinName ssel = NC);

    /** Create a SPI master connected to the specified pins.
     *
     *  @note This constructor manipulates the SSEL pin as a GPIO output
     *  using a DigitalOut object. This should work on any target, and permits
     *  the use of select() and deselect() methods to keep the pin asserted
     *  between transfers.
     *
     *  @note You can specify mosi or miso as NC if not used.
     *
     *  @param mosi SPI Master Out, Slave In pin.
     *  @param miso SPI Master In, Slave Out pin.
     *  @param sclk SPI Clock pin.
     *  @param ssel SPI Chip Select pin.
     */
    SPI(PinName mosi, PinName miso, PinName sclk, PinName ssel, use_gpio_ssel_t);

    virtual ~SPI();

    /** Configure the data transmission format.
     *
     *  @param bits Number of bits per SPI frame (4 - 16).
     *  @param mode Clock polarity and phase mode (0 - 3).
     *
     * @code
     * mode | POL PHA
     * -----+--------
     *   0  |  0   0
     *   1  |  0   1
     *   2  |  1   0
     *   3  |  1   1
     * @endcode
     */
    void format(int bits, int mode = 0);

    /** Set the SPI bus clock frequency.
     *
     *  @param hz Clock frequency in Hz (default = 1MHz).
     */
    void frequency(int hz = 1000000);

    /** Write to the SPI Slave and return the response.
     *
     *  @param value Data to be sent to the SPI slave.
     *
     *  @return Response from the SPI slave.
     */
    virtual int write(int value);

    /** Write to the SPI Slave and obtain the response.
     *
     *  The total number of bytes sent and received will be the maximum of
     *  tx_length and rx_length. The bytes written will be padded with the
     *  value 0xff.
     *
     *  @param tx_buffer Pointer to the byte-array of data to write to the device.
     *  @param tx_length Number of bytes to write, may be zero.
     *  @param rx_buffer Pointer to the byte-array of data to read from the device.
     *  @param rx_length Number of bytes to read, may be zero.
     *  @return
     *      The number of bytes written and read from the device. This is
     *      maximum of tx_length and rx_length.
     */
    virtual int write(const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length);

    /** Acquire exclusive access to this SPI bus.
     */
    virtual void lock(void);

    /** Release exclusive access to this SPI bus.
     */
    virtual void unlock(void);

    /** Assert the Slave Select line, acquiring exclusive access to this SPI bus.
     *
     * If use_gpio_ssel was not passed to the constructor, this only acquires
     * exclusive access; it cannot assert the Slave Select line.
     */
    void select(void);

    /** Deassert the Slave Select line, releasing exclusive access to this SPI bus.
     */
    void deselect(void);

    /** Set default write data.
      * SPI requires the master to send some data during a read operation.
      * Different devices may require different default byte values.
      * For example: A SD Card requires default bytes to be 0xFF.
      *
      * @param data Default character to be transmitted during a read operation.
      */
    void set_default_write_value(char data);

#if DEVICE_SPI_ASYNCH

    /** Start non-blocking SPI transfer using 8bit buffers.
     *
     * This function locks the deep sleep until any event has occurred.
     *
     * @param tx_buffer The TX buffer with data to be transferred. If NULL is passed,
     *                  the default SPI value is sent.
     * @param tx_length The length of TX buffer in bytes.
     * @param rx_buffer The RX buffer which is used for received data. If NULL is passed,
     *                  received data are ignored.
     * @param rx_length The length of RX buffer in bytes.
     * @param callback  The event callback function.
     * @param event     The event mask of events to modify. @see spi_api.h for SPI events.
     *
     * @return Operation result.
     * @retval 0 If the transfer has started.
     * @retval -1 If SPI peripheral is busy.
     */
    template<typename Type>
    int transfer(const Type *tx_buffer, int tx_length, Type *rx_buffer, int rx_length, const event_callback_t &callback, int event = SPI_EVENT_COMPLETE)
    {
        if (spi_active(&_peripheral->spi)) {
            return queue_transfer(tx_buffer, tx_length, rx_buffer, rx_length, sizeof(Type) * 8, callback, event);
        }
        start_transfer(tx_buffer, tx_length, rx_buffer, rx_length, sizeof(Type) * 8, callback, event);
        return 0;
    }

    /** Abort the on-going SPI transfer, and continue with transfers in the queue, if any.
     */
    void abort_transfer();

    /** Clear the queue of transfers.
     */
    void clear_transfer_buffer();

    /** Clear the queue of transfers and abort the on-going transfer.
     */
    void abort_all_transfers();

    /** Configure DMA usage suggestion for non-blocking transfers.
     *
     *  @param usage The usage DMA hint for peripheral.
     *
     *  @return Result of the operation.
     *  @retval 0 The usage was set.
     *  @retval -1 Usage cannot be set as there is an ongoing transaction.
     */
    int set_dma_usage(DMAUsage usage);

#if !defined(DOXYGEN_ONLY)
protected:

    /** SPI interrupt handler.
     */
    void irq_handler_asynch(void);

    /** Start the transfer or put it on the queue.
     *
     * @param tx_buffer The TX buffer with data to be transferred. If NULL is passed,
     *                  the default SPI value is sent
     * @param tx_length The length of TX buffer in bytes.
     * @param rx_buffer The RX buffer which is used for received data. If NULL is passed,
     *                  received data are ignored.
     * @param rx_length The length of RX buffer in bytes.
     * @param bit_width The buffers element width in bits.
     * @param callback  The event callback function.
     * @param event     The event mask of events to modify.
     *
     * @return Operation success.
     * @retval 0 A transfer was started or added to the queue.
     * @retval -1 Transfer can't be added because queue is full.
     */
    int transfer(const void *tx_buffer, int tx_length, void *rx_buffer, int rx_length, unsigned char bit_width, const event_callback_t &callback, int event);

    /** Put a transfer on the transfer queue.
     *
     * @param tx_buffer The TX buffer with data to be transferred. If NULL is passed,
     *                  the default SPI value is sent.
     * @param tx_length The length of TX buffer in bytes.
     * @param rx_buffer The RX buffer which is used for received data. If NULL is passed,
     *                  received data are ignored.
     * @param rx_length The length of RX buffer in bytes.
     * @param bit_width The buffers element width in bits.
     * @param callback  The event callback function.
     * @param event     The event mask of events to modify.
     *
     * @return Operation success.
     * @retval 0 A transfer was added to the queue.
     * @retval -1 Transfer can't be added because queue is full.
     */
    int queue_transfer(const void *tx_buffer, int tx_length, void *rx_buffer, int rx_length, unsigned char bit_width, const event_callback_t &callback, int event);

    /** Configure a callback, SPI peripheral, and initiate a new transfer.
     *
     * @param tx_buffer The TX buffer with data to be transferred. If NULL is passed,
     *                  the default SPI value is sent.
     * @param tx_length The length of TX buffer in bytes.
     * @param rx_buffer The RX buffer which is used for received data. If NULL is passed,
     *                  received data are ignored.
     * @param rx_length The length of RX buffer in bytes.
     * @param bit_width The buffers element width.
     * @param callback  The event callback function.
     * @param event     The event mask of events to modify.
     */
    void start_transfer(const void *tx_buffer, int tx_length, void *rx_buffer, int rx_length, unsigned char bit_width, const event_callback_t &callback, int event);

private:
    /** Lock deep sleep only if it is not yet locked */
    void lock_deep_sleep();

    /** Unlock deep sleep in case it is locked */
    void unlock_deep_sleep();


#if TRANSACTION_QUEUE_SIZE_SPI
    /** Start a new transaction.
     *
     *  @param data Transaction data.
     */
    void start_transaction(transaction_t *data);

    /** Dequeue a transaction and start the transfer if there was one pending.
     */
    void dequeue_transaction();

#endif // TRANSACTION_QUEUE_SIZE_SPI
#endif // !defined(DOXYGEN_ONLY)
#endif // DEVICE_SPI_ASYNCH

#if !defined(DOXYGEN_ONLY)
protected:
#ifdef DEVICE_SPI_COUNT
    // HAL must have defined this as a global enum
    typedef ::SPIName SPIName;
#else
    // HAL may or may not have defined it - use a local definition
    enum SPIName { GlobalSPI };
#endif

    // All members of spi_peripheral_s must be initialized to make the structure
    // constant-initialized, and hence able to be omitted by the linker,
    // as SingletonPtr now relies on C++ constant-initialization. (Previously it
    // worked through C++ zero-initialization). And all the constants should be zero
    // to ensure it stays in the actual zero-init part of the image if used, avoiding
    // an initialized-data cost.
    struct spi_peripheral_s {
        /* Internal SPI name identifying the resources. */
        SPIName name = SPIName(0);
        /* Internal SPI object handling the resources' state. */
        spi_t spi{};
        /* Used by lock and unlock for thread safety */
        SingletonPtr<PlatformMutex> mutex;
        /* Current user of the SPI */
        SPI *owner = nullptr;
#if DEVICE_SPI_ASYNCH && TRANSACTION_QUEUE_SIZE_SPI
        /* Queue of pending transfers */
        SingletonPtr<CircularBuffer<Transaction<SPI>, TRANSACTION_QUEUE_SIZE_SPI> > transaction_buffer;
#endif
    };

    // holds spi_peripheral_s per peripheral on the device.
    // Drawback: it costs ram size even if the device is not used, however
    // application can limit the allocation via JSON.
    static spi_peripheral_s _peripherals[SPI_PERIPHERALS_USED];
    static int _peripherals_used;

    // Holds the reference to the associated peripheral.
    spi_peripheral_s *_peripheral;

#if DEVICE_SPI_ASYNCH
    /* Interrupt */
    CThunk<SPI> _irq;
    /* Interrupt handler callback */
    event_callback_t _callback;
    /* Current preferred DMA mode @see dma_api.h */
    DMAUsage _usage;
    /* Current sate of the sleep manager */
    bool _deep_sleep_locked;
#endif // DEVICE_SPI_ASYNCH

    // Configuration.
    PinName _mosi;
    PinName _miso;
    PinName _sclk;
    PinName _hw_ssel;

    // The Slave Select GPIO if we're doing it ourselves.
    DigitalOut _sw_ssel;

    /* Size of the SPI frame */
    int _bits;
    /* Clock polairy and phase */
    int _mode;
    /* Clock frequency */
    int _hz;
    /* Default character used for NULL transfers */
    char _write_fill;
    /* Select count to handle re-entrant selection */
    int8_t _select_count;

private:
    void _do_construct();

    /** Private acquire function without locking/unlocking.
     *  Implemented in order to avoid duplicate locking and boost performance.
     */
    void _acquire(void);
    void _set_ssel(int);

    /** Private lookup in the static _peripherals table.
     */
    static spi_peripheral_s *_lookup(SPIName name);
    /** Allocate an entry in the static _peripherals table.
     */
    static spi_peripheral_s *_alloc();

#endif //!defined(DOXYGEN_ONLY)
};

/** @}*/

} // namespace mbed

#endif // DEVICE_SPI || DOXYGEN_ONLY

#endif // MBED_SPI_H