Jack Berkhout / BurstSPI

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Dependents:   20180621_FT813

Fork of BurstSPI by Erik -

BurstSPI.h@3:7d9b64d67b22, 2013-07-04 (annotated)

Committer:
Sissors
Date:
Thu Jul 04 19:03:58 2013 +0000
Revision:
3:7d9b64d67b22
Parent:
2:a8e55f7cbfee
Child:
14:35df38577abd
Refactored code, added version 1 of KL25Z support

Who changed what in which revision?

UserRevisionLine numberNew contents of line
Sissors 0:600eecd89a78 1 #ifndef BURSTSPI_H
Sissors 0:600eecd89a78 2 #define BURSTSPI_H
Sissors 0:600eecd89a78 3
Sissors 0:600eecd89a78 4 #include "mbed.h"
Sissors 0:600eecd89a78 5
Sissors 0:600eecd89a78 6
Sissors 0:600eecd89a78 7 /** An SPI Master, used for communicating with SPI slave devices at very high speeds
Sissors 0:600eecd89a78 8 *
frankvnk 2:a8e55f7cbfee 9 * The default mbed SPI class allows for communication via the SPI bus at high clock frequencies,
frankvnk 2:a8e55f7cbfee 10 * however at these frequencies there is alot of overhead from the mbed code.
frankvnk 2:a8e55f7cbfee 11 * While this code makes sure your code is alot more robust, it is also relative slow.
frankvnk 2:a8e55f7cbfee 12 * This library adds to your default SPI commands some extra commands to transmit data rapidly with
frankvnk 2:a8e55f7cbfee 13 * very little overhead. Downsides are that currently it is TX only (all RX packets are discarded),
frankvnk 2:a8e55f7cbfee 14 * and it requires some extra commands.
Sissors 0:600eecd89a78 15 *
Sissors 0:600eecd89a78 16 * Example:
Sissors 0:600eecd89a78 17 * @code
Sissors 0:600eecd89a78 18 * //Send 1000 SPI packets as fast as possible
Sissors 0:600eecd89a78 19 * spi.setFormat();
Sissors 0:600eecd89a78 20 * for (int i = 0; i<1000; i++)
Sissors 0:600eecd89a78 21 * spi.fastWrite(data[i]);
Sissors 0:600eecd89a78 22 * spi.clearRX();
Sissors 0:600eecd89a78 23 * @endcode
Sissors 0:600eecd89a78 24 *
frankvnk 2:a8e55f7cbfee 25 * As an example, writing 76,800 16-bit data packets to an LCD screen at 48MHz requires 111ms with
frankvnk 2:a8e55f7cbfee 26 * the normal mbed library. With this library it takes 25ms, which is also the theoretical
Sissors 0:600eecd89a78 27 * amount of time it should take. If you are running at 1MHz this will do alot less.
Sissors 0:600eecd89a78 28 */
Sissors 3:7d9b64d67b22 29 class BurstSPI : public SPI
Sissors 3:7d9b64d67b22 30 {
Sissors 0:600eecd89a78 31 public:
Sissors 0:600eecd89a78 32 /** Create a SPI master connected to the specified pins
Sissors 0:600eecd89a78 33 *
Sissors 0:600eecd89a78 34 * Pin Options:
Sissors 0:600eecd89a78 35 * (5, 6, 7) or (11, 12, 13)
Sissors 0:600eecd89a78 36 *
Sissors 0:600eecd89a78 37 * mosi or miso can be specfied as NC if not used
Sissors 0:600eecd89a78 38 *
Sissors 0:600eecd89a78 39 * @param mosi SPI Master Out, Slave In pin
Sissors 0:600eecd89a78 40 * @param miso SPI Master In, Slave Out pin
Sissors 0:600eecd89a78 41 * @param sclk SPI Clock pin
Sissors 0:600eecd89a78 42 */
Sissors 3:7d9b64d67b22 43 BurstSPI(PinName mosi, PinName miso, PinName sclk) : SPI(mosi, miso, sclk) {};
Sissors 0:600eecd89a78 44
Sissors 0:600eecd89a78 45 /** Put data packet in the SPI TX FIFO buffer
Sissors 0:600eecd89a78 46 *
frankvnk 2:a8e55f7cbfee 47 * If there is no space in the FIFO buffer it will block until there is space.
frankvnk 2:a8e55f7cbfee 48 * The FIFO buffer will automatically send the packets. There is no receiving here, only transmitting.
Sissors 0:600eecd89a78 49 *
Sissors 0:600eecd89a78 50 * @param data Data to be sent to the SPI slave
Sissors 0:600eecd89a78 51 */
Sissors 0:600eecd89a78 52 void fastWrite(int data);
Sissors 3:7d9b64d67b22 53
Sissors 0:600eecd89a78 54 /** Use this function before fastWrite to set the correct settings
Sissors 3:7d9b64d67b22 55 *
frankvnk 2:a8e55f7cbfee 56 * It is not needed to use this if the last SPI commands were either normal SPI transmissions,
frankvnk 2:a8e55f7cbfee 57 * or setting different format/frequency for this object. It is required to call this
frankvnk 2:a8e55f7cbfee 58 * function when several SPI objects use the same peripheral, and your last transmission was
frankvnk 2:a8e55f7cbfee 59 * from a different object with different settings. Not sure if you should use it?
Sissors 0:600eecd89a78 60 * Use it, it takes very little time to execute, so can't hurt.
Sissors 0:600eecd89a78 61 */
Sissors 3:7d9b64d67b22 62 void setFormat( void ) {
Sissors 3:7d9b64d67b22 63 format(_bits, _mode);
Sissors 3:7d9b64d67b22 64 frequency(_hz);
Sissors 3:7d9b64d67b22 65 }
Sissors 3:7d9b64d67b22 66
Sissors 0:600eecd89a78 67 /** After you are done with fastWrite, call this function
Sissors 0:600eecd89a78 68 *
frankvnk 2:a8e55f7cbfee 69 * FastWrite simply fills the SPI's (SSP's actually) TX FIFO buffer as fast as it can,
frankvnk 2:a8e55f7cbfee 70 * and that is the only thing it does. It doesn't do anything with received packages (currently, may change),
frankvnk 2:a8e55f7cbfee 71 * so the the RX buffer is full with unneeded packets. This function waits until transmission is finished,
frankvnk 2:a8e55f7cbfee 72 * and clears the RX buffer. You always have to call this before you want to receive
Sissors 0:600eecd89a78 73 * SPI data after using fastWrite.
Sissors 3:7d9b64d67b22 74 */
Sissors 0:600eecd89a78 75 void clearRX( void );
Sissors 3:7d9b64d67b22 76
Sissors 3:7d9b64d67b22 77
Sissors 0:600eecd89a78 78 //Just for documentation:
Sissors 3:7d9b64d67b22 79 #if 0
Sissors 0:600eecd89a78 80 /** Configure the data transmission format
Sissors 0:600eecd89a78 81 *
Sissors 0:600eecd89a78 82 * @param bits Number of bits per SPI frame (4 - 16)
Sissors 0:600eecd89a78 83 * @param mode Clock polarity and phase mode (0 - 3)
Sissors 0:600eecd89a78 84 *
Sissors 0:600eecd89a78 85 * @code
Sissors 3:7d9b64d67b22 86 * mode | POL PHA
Sissors 3:7d9b64d67b22 87 * -----+--------
Sissors 3:7d9b64d67b22 88 * 0 | 0 0
Sissors 0:600eecd89a78 89 * 1 | 0 1
Sissors 3:7d9b64d67b22 90 * 2 | 1 0
Sissors 0:600eecd89a78 91 * 3 | 1 1
Sissors 0:600eecd89a78 92 * @endcode
Sissors 0:600eecd89a78 93 */
Sissors 0:600eecd89a78 94 void format(int bits, int mode = 0);
Sissors 3:7d9b64d67b22 95
Sissors 0:600eecd89a78 96 /** Set the spi bus clock frequency
Sissors 0:600eecd89a78 97 *
Sissors 0:600eecd89a78 98 * @param hz SCLK frequency in hz (default = 1MHz)
Sissors 0:600eecd89a78 99 */
Sissors 0:600eecd89a78 100 void frequency(int hz = 1000000);
Sissors 3:7d9b64d67b22 101
Sissors 0:600eecd89a78 102 /** Write to the SPI Slave and return the response
Sissors 0:600eecd89a78 103 *
Sissors 0:600eecd89a78 104 * @param value Data to be sent to the SPI slave
Sissors 0:600eecd89a78 105 *
Sissors 0:600eecd89a78 106 * @returns
Sissors 0:600eecd89a78 107 * Response from the SPI slave
Sissors 0:600eecd89a78 108 */
Sissors 0:600eecd89a78 109 virtual int write(int value);
Sissors 3:7d9b64d67b22 110 #endif
Sissors 0:600eecd89a78 111
Sissors 0:600eecd89a78 112 };
Sissors 0:600eecd89a78 113
Sissors 0:600eecd89a78 114 #endif