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