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