spi.c
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/*
* Copyright (C) 2015 Daniel Amkaer Sorensen
* 2016 Freie Universität Berlin
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License v2.1. See the file LICENSE in the top level
* directory for more details.
*/
/**
* @ingroup driver_periph
* @{
*
* @file
* @brief Low-level SPI driver implementation for ATmega family
*
* @author Daniel Amkaer Sorensen <daniel.amkaer@gmail.com>
* @author Hauke Petersen <hauke.petersen@fu-berlin.de>
*
* @}
*/
#include "cpu.h"
#include "mutex.h"
#include "periph/spi.h"
#define ENABLE_DEBUG (0)
#include "debug.h"
/* guard this file in case no SPI device is defined */
#if SPI_NUMOF
/**
* @brief Extract BR0, BR1 and SPI2X bits from speed value
* @{
*/
#define SPEED_MASK (0x3)
#define S2X_SHIFT (2)
/** @} */
static mutex_t lock = MUTEX_INIT;
int spi_init_master(spi_t dev, spi_conf_t conf, spi_speed_t speed)
{
DEBUG("spi.c: conf = %d, speed = %d\n", conf, speed);
/* make sure device is valid (there is only one...) */
if (dev != 0) {
return -1;
}
/* the pin configuration for this CPU is fixed:
* - PB3: MISO (configure as input - done automatically)
* - PB2: MOSI (configure as output)
* - PB1: SCK (configure as output)
* - PB0: SS (configure as output, but unused)
*
* The SS pin must be configured as output for the SPI device to work as
* master correctly, though we do not use it for now (as we handle the chip
* select externally for now)
*/
DDRB |= ((1 << DDB2) | (1 << DDB1) | (1 << DDB0));
/* make sure the SPI is not powered off */
MEGA_PRR &= ~(1 << PRSPI);
/* configure as master, with given mode and clock */
SPSR = (speed >> S2X_SHIFT);
SPCR = ((1 << SPE) | (1 << MSTR) | conf | (speed & SPEED_MASK));
/* clear interrupt flag by reading SPSR */
(void)SPSR;
/* clear data register */
(void)SPDR;
return 0;
}
int spi_acquire(spi_t dev)
{
mutex_lock(&lock);
return 0;
}
int spi_release(spi_t dev)
{
mutex_unlock(&lock);
return 0;
}
int spi_init_slave(spi_t dev, spi_conf_t conf, char (*cb)(char data))
{
(void) dev;
(void) conf;
(void) cb;
/* not implemented */
return -1;
}
void spi_transmission_begin(spi_t dev, char reset_val)
{
(void)dev;
(void)reset_val;
/* not implemented */
}
int spi_transfer_byte(spi_t dev, char out, char *in)
{
return spi_transfer_bytes(dev, &out, in, 1);
}
int spi_transfer_bytes(spi_t dev, char *out, char *in, unsigned int length)
{
for (unsigned int i = 0; i < length; i++) {
char tmp = (out) ? out[i] : 0;
SPDR = tmp;
while (!(SPSR & (1 << SPIF))) {}
tmp = SPDR;
if (in) {
in[i] = tmp;
}
}
return (int)length;
}
int spi_transfer_reg(spi_t dev, uint8_t reg, char out, char *in)
{
spi_transfer_bytes(dev, (char *)®, NULL, 1);
return spi_transfer_bytes(dev, &out, in, 1);
}
int spi_transfer_regs(spi_t dev, uint8_t reg, char *out, char *in, unsigned int length)
{
spi_transfer_bytes(dev, (char *)®, NULL, 1);
return spi_transfer_bytes(dev, out, in, length);
}
void spi_poweron(spi_t dev)
{
SPCR |= (1 << SPE);
}
void spi_poweroff(spi_t dev)
{
SPCR &= ~(1 << SPE);
}
#endif /* SPI_NUMOF */