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_ */ 74