Diff: drivers/SPI.h

Revision:

188:bcfe06ba3d64

Parent:

187:0387e8f68319

Child:

189:f392fc9709a3

--- a/drivers/SPI.h	Thu Sep 06 13:40:20 2018 +0100
+++ b/drivers/SPI.h	Thu Nov 08 11:46:34 2018 +0000
@@ -36,39 +36,44 @@
 namespace mbed {
 /** \addtogroup drivers */
 
-/** A SPI Master, used for communicating with SPI slave devices
+/** 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
+ * 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
+ * can be controlled using DigitalOut pins.
  *
  * @note Synchronization level: Thread safe
  *
- * Example:
+ * Example of how to send a byte to a SPI slave and record the response:
  * @code
- * // Send a byte to a SPI slave, and record the response
- *
  * #include "mbed.h"
  *
- * // hardware ssel (where applicable)
- * //SPI device(p5, p6, p7, p8); // mosi, miso, sclk, ssel
+ * SPI device(SPI_MOSI, SPI_MISO, SPI_SCLK)
  *
- * // software ssel
- * SPI device(p5, p6, p7); // mosi, miso, sclk
- * DigitalOut cs(p8); // ssel
+ * DigitalOut chip_select(SPI_CS);
  *
  * int main() {
- *     // hardware ssel (where applicable)
- *     //int response = device.write(0xFF);
- *
  *     device.lock();
- *     // software ssel
- *     cs = 0;
+ *     chip_select = 0;
+ *
  *     int response = device.write(0xFF);
- *     cs = 1;
+ *
+ *     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
  * @ingroup drivers
@@ -77,21 +82,22 @@
 
 public:
 
-    /** Create a SPI master connected to the specified pins
+    /** Create a SPI master connected to the specified pins.
      *
-     *  mosi or miso can be specified as NC if not used
+     *  @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
+     *  @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);
+    virtual ~SPI();
 
-    /** Configure the data transmission format
+    /** Configure the data transmission format.
      *
-     *  @param bits Number of bits per SPI frame (4 - 16)
-     *  @param mode Clock polarity and phase mode (0 - 3)
+     *  @param bits Number of bits per SPI frame (4 - 16).
+     *  @param mode Clock polarity and phase mode (0 - 3).
      *
      * @code
      * mode | POL PHA
@@ -104,51 +110,50 @@
      */
     void format(int bits, int mode = 0);
 
-    /** Set the spi bus clock frequency
+    /** Set the SPI bus clock frequency.
      *
-     *  @param hz SCLK frequency in hz (default = 1MHz)
+     *  @param hz Clock frequency in Hz (default = 1MHz).
      */
     void frequency(int hz = 1000000);
 
-    /** Write to the SPI Slave and return the response
+    /** Write to the SPI Slave and return the response.
      *
-     *  @param value Data to be sent to the SPI slave
+     *  @param value Data to be sent to the SPI slave.
      *
-     *  @returns
-     *    Response from the SPI slave
+     *  @return Response from the SPI slave.
      */
     virtual int write(int value);
 
-    /** Write to the SPI Slave and obtain the response
+    /** 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
-     *  @returns
+     *  @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
+    /** Acquire exclusive access to this SPI bus.
      */
     virtual void lock(void);
 
-    /** Release exclusive access to this SPI bus
+    /** Release exclusive access to this SPI bus.
      */
     virtual void unlock(void);
 
-    /** Set default write data
+    /** 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 while read operation
+      * @param data Default character to be transmitted during a read operation.
       */
     void set_default_write_value(char data);
 
@@ -156,17 +161,20 @@
 
     /** Start non-blocking SPI transfer using 8bit buffers.
      *
-     * This function locks the deep sleep until any event has occurred
+     * This function locks the deep sleep until any event has occurred.
      *
-     * @param tx_buffer The TX buffer with data to be transfered. If NULL is passed,
-     *                  the default SPI value is sent
-     * @param tx_length The length of TX buffer in bytes
+     * @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 logical OR of events to modify. Look at spi hal header file for SPI events.
-     * @return Zero if the transfer has started, or -1 if SPI peripheral is busy
+     *                  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)
@@ -178,75 +186,85 @@
         return 0;
     }
 
-    /** Abort the on-going SPI transfer, and continue with transfer's in the queue if any.
+    /** Abort the on-going SPI transfer, and continue with transfers in the queue, if any.
      */
     void abort_transfer();
 
-    /** Clear the transaction buffer
+    /** Clear the queue of transfers.
      */
     void clear_transfer_buffer();
 
-    /** Clear the transaction buffer and abort on-going transfer.
+    /** Clear the queue of transfers and abort the on-going transfer.
      */
     void abort_all_transfers();
 
-    /** Configure DMA usage suggestion for non-blocking transfers
+    /** Configure DMA usage suggestion for non-blocking transfers.
+     *
+     *  @param usage The usage DMA hint for peripheral.
      *
-     *  @param usage The usage DMA hint for peripheral
-     *  @return Zero if the usage was set, -1 if a transaction is on-going
-    */
+     *  @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);
 
 protected:
-    /** SPI IRQ handler
-     *
-    */
+    /** SPI interrupt handler.
+     */
     void irq_handler_asynch(void);
 
-    /** Common transfer method
+    /** Start the transfer or put it on the queue.
      *
-     * @param tx_buffer The TX buffer with data to be transfered. If NULL is passed,
+     * @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 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 logical OR of events to modify
-     * @return Zero if the transfer has started or was added to the queue, or -1 if SPI peripheral is busy/buffer is full
-    */
+     *                  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 transfered. If NULL is passed,
-     *                  the default SPI value is sent
-     * @param tx_length The length of TX buffer in bytes
+     * @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 logical OR of events to modify
-     * @return Zero if a transfer was added to the queue, or -1 if the queue is full
-    */
+     *                  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);
 
-    /** Configures a callback, spi peripheral and initiate a new transfer
+    /** Configure a callback, SPI peripheral, and initiate a new transfer.
      *
-     * @param tx_buffer The TX buffer with data to be transfered. If NULL is passed,
-     *                  the default SPI value is sent
-     * @param tx_length The length of TX buffer in bytes
+     * @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 logical OR of events to modify
-    */
+     *                  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);
 
+#if !defined(DOXYGEN_ONLY)
+
 private:
     /** Lock deep sleep only if it is not yet locked */
     void lock_deep_sleep();
@@ -257,49 +275,63 @@
 
 #if TRANSACTION_QUEUE_SIZE_SPI
 
-    /** Start a new transaction
+    /** Start a new transaction.
      *
-     *  @param data Transaction data
-    */
+     *  @param data Transaction data.
+     */
     void start_transaction(transaction_t *data);
 
-    /** Dequeue a transaction
-     *
-    */
+    /** Dequeue a transaction and start the transfer if there was one pending.
+     */
     void dequeue_transaction();
+
+    /* Queue of pending transfers */
     static CircularBuffer<Transaction<SPI>, TRANSACTION_QUEUE_SIZE_SPI> _transaction_buffer;
 #endif
 
-#endif
+#endif //!defined(DOXYGEN_ONLY)
 
-public:
-    virtual ~SPI()
-    {
-    }
+#endif //DEVICE_SPI_ASYNCH
+
+#if !defined(DOXYGEN_ONLY)
 
 protected:
+    /* Internal SPI object identifying the resources */
     spi_t _spi;
 
 #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
 
+    /* Take over the physical SPI and apply our settings (thread safe) */
     void aquire(void);
+    /* Current user of the SPI */
     static SPI *_owner;
+    /* Used by lock and unlock for thread safety */
     static SingletonPtr<PlatformMutex> _mutex;
+    /* 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;
 
 private:
-    /* Private acquire function without locking/unlocking
-     * Implemented in order to avoid duplicate locking and boost performance
+    /** Private acquire function without locking/unlocking.
+     *  Implemented in order to avoid duplicate locking and boost performance.
      */
     void _acquire(void);
+
+#endif //!defined(DOXYGEN_ONLY)
 };
 
 } // namespace mbed