include/spi.h

   1 /*
   2  * (C) Copyright 2001
   3  * Gerald Van Baren, Custom IDEAS, vanbaren@cideas.com.
   4  *
   5  * See file CREDITS for list of people who contributed to this
   6  * project.
   7  *
   8  * This program is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU General Public License as
  10  * published by the Free Software Foundation; either version 2 of
  11  * the License, or (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with this program; if not, write to the Free Software
  20  * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
  21  * MA 02111-1307 USA
  22  */
  23
  24 #ifndef _SPI_H_
  25 #define _SPI_H_
  26
  27 /*
  28  * The function call pointer type used to drive the chip select.
  29  */
  30 typedef void (*spi_chipsel_type)(int cs);
  31
  32
  33 /*-----------------------------------------------------------------------
  34  * Initialization, must be called once on start up.
  35  */
  36 void spi_init(void);
  37
  38
  39 /*-----------------------------------------------------------------------
  40  * SPI transfer
  41  *
  42  * This writes "bitlen" bits out the SPI MOSI port and simultaneously clocks
  43  * "bitlen" bits in the SPI MISO port.  That's just the way SPI works.
  44  *
  45  * The source of the outgoing bits is the "dout" parameter and the
  46  * destination of the input bits is the "din" parameter.  Note that "dout"
  47  * and "din" can point to the same memory location, in which case the
  48  * input data overwrites the output data (since both are buffered by
  49  * temporary variables, this is OK).
  50  *
  51  * If the chipsel() function is not NULL, it is called with a parameter
  52  * of '1' (chip select active) at the start of the transfer and again with
  53  * a parameter of '0' at the end of the transfer.
  54  *
  55  * If the chipsel() function _is_ NULL, it the responsibility of the
  56  * caller to make the appropriate chip select active before calling
  57  * spi_xfer() and making it inactive after spi_xfer() returns.
  58  *
  59  * spi_xfer() interface:
  60  *   chipsel: Routine to call to set/clear the chip select:
  61  *              if chipsel is NULL, it is not used.
  62  *              if(cs),  make the chip select active (typically '0').
  63  *              if(!cs), make the chip select inactive (typically '1').
  64  *   dout:    Pointer to a string of bits to send out.  The bits are
  65  *              held in a byte array and are sent MSB first.
  66  *   din:     Pointer to a string of bits that will be filled in.
  67  *   bitlen:  How many bits to write and read.
  68  *
  69  *   Returns: 0 on success, not 0 on failure
  70  */
  71 int  spi_xfer(spi_chipsel_type chipsel, int bitlen, uchar *dout, uchar *din);
  72
  73 #endif  /* _SPI_H_ */