SPIHalfDuplex.h

00001 /* mbed Microcontroller Library - SPIHalfDuplex
00002  * Copyright (c) 2010-2011 ARM Limited. All rights reserved.
00003  */
00004 
00005 #ifndef MBED_SPIHALFDUPLEX_H
00006 #define MBED_SPIHALFDUPLEX_H
00007 
00008 #include "device.h"
00009 
00010 #if DEVICE_SPI
00011 
00012 #include "SPI.h"
00013 
00014 namespace mbed {
00015 
00016 /** A SPI half-duplex master, used for communicating with SPI slave devices
00017  *  over a shared data line.
00018  *
00019  *  The default format is set to 8-bits for both master and slave, and a
00020  *  clock frequency of 1MHz
00021  *
00022  *  Most SPI devies will also require Chip Select and Reset signals. These
00023  *  can be controlled using <DigitalOut> pins.
00024  *
00025  *  Although this is for a shared data line, both MISO and MOSI are defined,
00026  *  and should be tied together externally to the mbed. This class handles
00027  *  the tri-stating of the MOSI pin.
00028  *
00029  * Example:
00030  * @code
00031  * // Send a byte to a SPI half-duplex slave, and record the response
00032  *
00033  * #include "mbed.h"
00034  * 
00035  * SPIHalfDuplex device(p5, p6, p7) // mosi, miso, sclk
00036  *
00037  * int main() {
00038  *     int respone = device.write(0xAA);
00039  * }
00040  * @endcode
00041  */
00042 
00043 class SPIHalfDuplex : public SPI {
00044 
00045 public:
00046     
00047     /** Create a SPI half-duplex master connected to the specified pins
00048      *
00049      *  Pin Options:
00050      *    (5, 6, 7) or (11, 12, 13)
00051      *
00052      *  mosi or miso can be specfied as NC if not used
00053      *
00054      *  @param mosi SPI Master Out, Slave In pin
00055      *  @param miso SPI Master In, Slave Out pin
00056      *  @param sclk SPI Clock pin
00057      *  @param name (optional) A string to identify the object
00058      */
00059     SPIHalfDuplex(PinName mosi, PinName miso, PinName sclk,
00060         const char *name = NULL);
00061 
00062 #if 0 // Inherited from SPI - documentation only
00063     /** Configure the data transmission format
00064      *
00065      *  @param bits Number of bits per SPI frame (4 - 16)
00066      *  @param mode Clock polarity and phase mode (0 - 3)
00067      *
00068      * @code
00069      * mode | POL PHA
00070      * -----+--------
00071      *   0  |  0   0
00072      *   1  |  0   1
00073      *   2  |  1   0
00074      *   3  |  1   1
00075      * @endcode
00076      */
00077     void format(int bits, int mode = 0);
00078 
00079     /** Set the spi bus clock frequency
00080      *
00081      *  @param hz SCLK frequency in hz (default = 1MHz)
00082      */
00083     void frequency(int hz = 1000000);
00084 #endif
00085 
00086     /** Write to the SPI Slave and return the response
00087      *
00088      *  @param value Data to be sent to the SPI slave
00089      *
00090      *  @returns
00091      *    Response from the SPI slave
00092      */
00093     virtual int write(int value);
00094     
00095     /** Set the number of databits expected from the slave, from 4-16
00096      *
00097      *  @param sbits Number of expected bits in the slave response
00098      */
00099     void slave_format(int sbits);
00100 
00101 protected:
00102     PinName _mosi;
00103     PinName _miso;
00104     int     _sbits;
00105 
00106 }; // End of class
00107 
00108 } // End of namespace mbed
00109 
00110 #endif
00111 
00112 #endif