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79 lines
1.4 KiB
79 lines
1.4 KiB
15 years ago
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#include <avr/io.h>
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#include <stdint.h>
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#include <math.h>
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#include <spi.h>
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/* SPI framework.
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*
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* currently alpha, uses interrupts, single master/single slave operation
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*/
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uint8_t * volatile spi_writeptr;
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uint8_t * volatile spi_readptr;
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uint8_t volatile spi_writelen;
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uint8_t volatile spi_readlen;
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uint8_t spi_readbuf[SPI_READBUF_LEN];
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void spi_init(){
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uint8_t spcr, spsr, d;
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/* calculate clock divisor,
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* gcc with optimize will do that calculation compile-time. */
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uint8_t spi_clock_divisor(){
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double d;
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d = F_CPU / SPI_BAUDRATE;
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d = ceil((log(d)/log(2))*0.95); // clock needs dividing by 2^d
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// the 0.95 to avoid ceil issues
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return d-1; // the -1 because minimum divisor is /2
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}
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d = spi_clock_divisor();
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if(d>7){
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#warning "spi baudrate too slow, cannot be set"
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d=7;
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}
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//TODO: DDRs setzen
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spsr = 0;
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spsr |= (d & 1) ? 0 : _BV(SPI2X);
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spcr = 0 | _BV(SPIE) | _BV(SPE);
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spcr |= (d & 2) ? _BV(SPR0) : 0;
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spcr |= (d & 4) ? _BV(SPR1) : 0;
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#ifdef SPI_MASTER
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spcr |= _BV(MSTR);
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#endif
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SPCR = spcr;
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SPSR = spsr;
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// initialize interface for ISR:
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spi_readptr = spi_readbuf;
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spi_readlen = SPI_READBUF_LEN;
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spi_writeptr = NULL;
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}
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// return true on success, false on error
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uint8_t spi_write(uint8_t *data, uint8_t len){
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if(spi_writeptr != NULL){
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return 0
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}
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spi_writeptr = data;
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spi_writelen = len;
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//TODO: handle SS, write out first byte
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return 1;
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}
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#ifdef SPI_MASTER
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ISR(SPI_vector){
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}
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#endif //SPI_MASTER
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