swspi.h

00001 // Software (bit-banged) SPI Module supporting two CPHA modes and two
00002 // chip select signals.  Yields to allow use by different threads.
00003 //
00004 
00005 #ifndef sw_spi_h
00006 #define sw_spi_h
00007 
00008 #include "mbed.h"
00009 #include <stdint.h>
00010 
00011 // This is the bit in the SPI address that marks it as a write
00012 #define SPI_WRITE_MASK 0x80
00013 
00014 
00015 /////////////////////////////////////////////////////////////////////
00016 /// \class swspi swspi.h <swspi.h>
00017 /// \brief bit-banged SPI
00018 
00019 class swspi
00020 {
00021 public:
00022     /// Constructor
00023     /// \param[in] mosiPin pin number for MOSI
00024     /// \param[in] misoPin pin number for MISO
00025     /// \param[in] sckPin pin number for SCK
00026     /// \param[in] ss1Pin pin number for Slave Select 1
00027     /// \param[in] ss2Pin pin number for Slave Select 2
00028     swspi(PinName mosiPin, PinName misoPin, PinName sckPin, PinName ss1Pin, PinName ss2Pin);
00029 
00030     /// Initialise the Driver transport hardware and software.
00031     /// Make sure the Driver is properly configured before calling init().
00032     void           init();
00033 
00034     /// Reads a single register from the SPI device
00035     /// \param[in] reg Register number
00036     /// \return The value of the register
00037     uint8_t        spiRead(uint8_t reg, int cpha, int ss);
00038 
00039     /// Writes a single byte to the SPI device
00040     /// \param[in] reg Register number
00041     /// \param[in] val The value to write
00042     /// \return Some devices return a status byte during the first data transfer. This byte is returned.
00043     ///  it may or may not be meaningfule depending on the the type of device being accessed.
00044     uint8_t           spiWrite(uint8_t reg, uint8_t val, int cpha, int ss);
00045 
00046     /// Reads a number of consecutive registers from the SPI device using burst read mode
00047     /// \param[in] reg Register number of the first register
00048     /// \param[in] dest Array to write the register values to. Must be at least len bytes
00049     /// \param[in] len Number of bytes to read
00050     /// \return Some devices return a status byte during the first data transfer. This byte is returned.
00051     ///  it may or may not be meaningfule depending on the the type of device being accessed.
00052     uint8_t           spiBurstRead(uint8_t reg, uint8_t* dest, uint8_t len, int cpha, int ss);
00053 
00054     /// Write a number of consecutive registers using burst write mode
00055     /// \param[in] reg Register number of the first register
00056     /// \param[in] src Array of new register values to write. Must be at least len bytes
00057     /// \param[in] len Number of bytes to write
00058     /// \return Some devices return a status byte during the first data transfer. This byte is returned.
00059     ///  it may or may not be meaningfule depending on the the type of device being accessed.
00060     uint8_t           spiBurstWrite(uint8_t reg, const uint8_t* src, uint8_t len, int cpha, int ss);
00061 
00062 protected:
00063 
00064     void _setSlaveSelect(int v);
00065     uint8_t _transfer(uint8_t v);
00066     
00067     /// Pins
00068     DigitalOut* mosiP;
00069     DigitalIn* misoP;
00070     DigitalOut* sckP;
00071     DigitalOut* ss1P;
00072     DigitalOut* ss2P;
00073     
00074     /// The current transfer data phase
00075     int                 _cpha;
00076     
00077     /// The current transfer slave select
00078     uint8_t             _ss;
00079     
00080     // Access control
00081     Mutex               _spi_mutex;
00082 };
00083 
00084 #endif