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74 lines
2.8 KiB
C
74 lines
2.8 KiB
C
/*
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* (C) Copyright 2001
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* Gerald Van Baren, Custom IDEAS, vanbaren@cideas.com.
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*
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* See file CREDITS for list of people who contributed to this
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* project.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of
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* the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston,
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* MA 02111-1307 USA
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*/
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#ifndef _SPI_H_
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#define _SPI_H_
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/*
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* The function call pointer type used to drive the chip select.
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*/
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typedef void (*spi_chipsel_type)(int cs);
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/*-----------------------------------------------------------------------
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* Initialization, must be called once on start up.
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*/
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void spi_init(void);
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/*-----------------------------------------------------------------------
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* SPI transfer
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*
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* This writes "bitlen" bits out the SPI MOSI port and simultaneously clocks
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* "bitlen" bits in the SPI MISO port. That's just the way SPI works.
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*
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* The source of the outgoing bits is the "dout" parameter and the
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* destination of the input bits is the "din" parameter. Note that "dout"
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* and "din" can point to the same memory location, in which case the
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* input data overwrites the output data (since both are buffered by
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* temporary variables, this is OK).
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*
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* If the chipsel() function is not NULL, it is called with a parameter
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* of '1' (chip select active) at the start of the transfer and again with
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* a parameter of '0' at the end of the transfer.
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*
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* If the chipsel() function _is_ NULL, it the responsibility of the
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* caller to make the appropriate chip select active before calling
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* spi_xfer() and making it inactive after spi_xfer() returns.
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*
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* spi_xfer() interface:
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* chipsel: Routine to call to set/clear the chip select:
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* if chipsel is NULL, it is not used.
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* if(cs), make the chip select active (typically '0').
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* if(!cs), make the chip select inactive (typically '1').
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* dout: Pointer to a string of bits to send out. The bits are
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* held in a byte array and are sent MSB first.
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* din: Pointer to a string of bits that will be filled in.
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* bitlen: How many bits to write and read.
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*
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* Returns: 0 on success, not 0 on failure
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*/
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int spi_xfer(spi_chipsel_type chipsel, int bitlen, uchar *dout, uchar *din);
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#endif /* _SPI_H_ */
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