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wdenk77f85582002-09-26 02:01:47 +00001/*
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 */
30typedef void (*spi_chipsel_type)(int cs);
31
32
33/*-----------------------------------------------------------------------
34 * Initialization, must be called once on start up.
35 */
36void 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 */
71int spi_xfer(spi_chipsel_type chipsel, int bitlen, uchar *dout, uchar *din);
72
73#endif /* _SPI_H_ */