porklib: Simple library for programming Arduino in C
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avr-lib/lib/spi.c

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#include <avr/io.h>
#include <stdint.h>
#include <stdbool.h>
#include "iopins.h"
#include "spi.h"
bool spi_inited = false;
/** Init SPI (for SD card communication) */
void spi_init()
{
if (spi_inited) return;
spi_inited = true;
// Pin configuration
as_output(PIN_SS);
as_output(PIN_MOSI);
as_output(PIN_SCK);
as_input_pu(PIN_MISO);
// Enable SPI, master, clock = F_CPU/128
SPCR = _BV(SPE) | _BV(MSTR) | _BV(SPR0) | _BV(SPR1);
}
/** Write a byte to SPI. Returns received byte. */
uint8_t spi_write(uint8_t b)
{
SPDR = b;
while (!(SPSR & _BV(SPIF)));
return SPDR;
}