Diff: BurstSPI.h

Revision:

0:600eecd89a78

Child:

1:5ef4a019e0db

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/BurstSPI.h	Thu Jan 03 09:14:10 2013 +0000
@@ -0,0 +1,101 @@
+#ifndef BURSTSPI_H
+#define BURSTSPI_H
+
+#include "mbed.h"
+
+
+/** An SPI Master, used for communicating with SPI slave devices at very high speeds
+ *
+ * The default mbed SPI class allows for communication via the SPI bus at high clock frequencies, however at these frequencies there is alot of overhead from the mbed code.
+ * While this code makes sure your code is alot more robust, it is also relative slow. This library adds to your default SPI commands some extra commands to transmit data rapidly with
+ * very little overhead. Downsides are that currently it is TX only (all RX packets are discarded), and it requires some extra commands.
+ *
+ * Example:
+ * @code
+ *  //Send 1000 SPI packets as fast as possible
+ *  spi.setFormat();
+ *  for (int i = 0; i<1000; i++)
+ *    spi.fastWrite(data[i]);
+ *  spi.clearRX();
+ * @endcode
+ *
+ * As an example, writing 76,800 16-bit data packets to an LCD screen at 48MHz requires 111ms with the normal mbed library. With this library it takes 25ms, which is also the theoretical
+ * amount of time it should take. If you are running at 1MHz this will do alot less.
+ */
+class BurstSPI : public SPI {
+public:
+    /** Create a SPI master connected to the specified pins
+    *
+    * Pin Options:
+    *  (5, 6, 7) or (11, 12, 13)
+    *
+    *  mosi or miso can be specfied 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
+    */
+    BurstSPI(PinName mosi, PinName miso, PinName sclk);
+
+    /** Put data packet in the SPI TX FIFO buffer
+    *
+    *  If there is no space in the FIFO buffer it will block until there is space. The FIFO buffer will automatically send the packets. There is no receiving here, only transmitting.
+    *
+    *  @param data Data to be sent to the SPI slave
+    */
+    void fastWrite(int data);
+    
+    /** Use this function before fastWrite to set the correct settings
+    * 
+    * It is not needed to use this if the last SPI commands were either normal SPI transmissions, or setting different format/frequency for this object. It is required to call this
+    * function when several SPI objects use the same peripheral, and your last transmission was from a different object with different settings. Not sure if you should use it?
+    * Use it, it takes very little time to execute, so can't hurt.
+    */
+    void setFormat( void );
+    
+    /** After you are done with fastWrite, call this function
+    *
+    * FastWrite simply fills the SPI's (SSP's actually) TX FIFO buffer as fast as it can, and that is the only thing it does. It doesn't do anything with received packages (currently, may change),
+    * so the the RX buffer is full with unneeded packets. This function waits until transmission is finished, and clears the RX buffer. You always have to call this before you want to receive
+    * SPI data after using fastWrite.
+    */    
+    void clearRX( void );
+    
+    
+    //Just for documentation:
+    #ifdef 0
+    /** 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 SCLK 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
+     *
+     *  @returns
+     *    Response from the SPI slave
+    */
+    virtual int write(int value);
+    #endif
+
+};
+
+#endif
\ No newline at end of file