99 lines
2.2 KiB
C
99 lines
2.2 KiB
C
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/**
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SPI methods are not interrupt driven - they wait until SPI operation completes.
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If you're using CMT and would prefer switching to another task while SPI operation
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is in progress, you can define SPI_USE_CMT in swdefs.h. This requires CMT_MUTEX_FUNC.
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Also, SS (CS) is not controlled by these methods. It's the responsibility of the user.
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@file spi.c
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@brief SPI routines
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@author Matej Kogovsek (matej@hamradio.si)
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@copyright LGPL 2.1
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@note This file is part of mat-stm32f1-lib
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*/
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#include <inttypes.h>
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#include <avr/io.h>
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#include <avr/interrupt.h>
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#include "spi.h"
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#include "hwdefs.h"
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#ifdef SPI_USE_CMT
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#warning SPI using cmt
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#include "cmt.h"
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struct cmt_mutex spi_mutex;
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#endif
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#ifndef SPCR0
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#define SPCR0 SPCR
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#define SPE0 SPE
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#define MSTR0 MSTR
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#define SPSR0 SPSR
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#define SPDR0 SPDR
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#define SPIF0 SPIF
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#endif
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/**
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@brief Initialize SPI interface.
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Although SPI can have different clock phase and polarity, I have never ran across anything that uses other
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than low polarity and 1st edge phase. Therefore these parameters are implied and not variable. As are 8 bit
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words and MSB first.
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@param[in] fdiv Baudrate prescaler, F_CPU dependent
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*/
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void spi_init(uint8_t fdiv)
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{
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if( SPCR0 & _BV(SPE0) ) return;
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#ifdef SPI_USE_CMT
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spi_mutex.ac = 0;
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#endif
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// make SCK, MOSI pins outputs and MISO an input
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SCK_DDR |= _BV(SCK_BIT);
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MOSI_DDR |= _BV(MOSI_BIT);
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MISO_DDR &= ~_BV(MISO_BIT);
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// init SPI, MSB first, SCK low when idle
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SPCR0 = _BV(SPE0) | _BV(MSTR0) | (fdiv & 3);
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SPSR0 = (fdiv >> 2) & 1;
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}
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/**
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@brief Send and receive byte (NSS not controlled)
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@param[in] d Byte to send
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@return byte received
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*/
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uint8_t spi_rw(uint8_t d)
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{
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#ifdef SPI_USE_CMT
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cmt_acquire(&spi_mutex);
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#endif
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SPCR0 |= _BV(MSTR0);
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SPDR0 = d;
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while( !(SPSR0 & _BV(SPIF0)) ) {
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#ifdef SPI_USE_CMT
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cmt_delay_ticks(0);
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#endif
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}
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d = SPDR0;
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#ifdef SPI_USE_CMT
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cmt_release(&spi_mutex);
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#endif
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return d;
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}
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// ------------------------------------------------------------------
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// INTERRUPTS
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// ------------------------------------------------------------------
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ISR(SPI_STC_vect)
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{
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//
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}
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