root / trunk / code / projects / libdragonfly / spi.c @ 1461
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/**
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* @file spi.c
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* @brief Basic SPI module to handle encoders
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* @author Colony Project, CMU Robotics Club
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* Need to move spi.h include into dragonfly_lib.h when stable
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**/
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#include <avr/interrupt.h> |
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#include "spi.h" |
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unsigned char spi_initd=0; |
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static volatile char spi_bytes; /* number of bytes to read */ |
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static spi_fun_recv_t spi_recv_func; /* byte handler */ |
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static spi_fun_recv_complete_t spi_recv_complete_func; /*transmission completion handler */ |
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/**
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* @brief Initialize SPI hardware for communication.
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*
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* @param recv_func The function to be called for each byte of data received.
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* @param recv_complete_func The function to be called at the end of a complete transmission.
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*
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* @return 0 if init succesfull, an error code otherwise
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*/
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int spi_init (spi_fun_recv_t recv_func, spi_fun_recv_complete_t recv_complete_func)
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{ |
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if(spi_initd) {
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return ERROR_INIT_ALREADY_INITD;
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} |
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/* Enable Interrupt, Enable SPI Module, MSB First, Master Mode, Clock div = 64 */
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SPCR = _BV(SPE) | _BV(SPIE) /*| _BV(DORD)*/ | _BV(MSTR) | _BV(SPR1) | _BV(SPR0);
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SPSR = _BV(SPI2X); |
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/* Set SCLK, SS, MOSI as outputs. MISO as input */
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DDRB |= MOSI | SCLK | SS; |
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DDRB &= ~MISO; |
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/* Keep SS high until transmit */
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PORTB |= SS; |
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/* set function to be executed when we receive a byte */
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spi_recv_func = recv_func; |
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spi_recv_complete_func = recv_complete_func; |
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spi_bytes = 0;
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//usb_puts("\tspi.c Debug: SPI INITIALIZED\n");
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spi_initd=1;
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return 0; |
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} |
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/**
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* @brief Transfer a given byte to slave and receive a byte
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*
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* @param bytes The number of bytes to be transferred.
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**/
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int spi_transfer(char bytes) |
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{ |
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if(!spi_initd)
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return ERROR_LIBRARY_NOT_INITD;
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spi_bytes = bytes; |
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PORTB &= ~SS; /* Set SS low to initiate transmission */
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SPDR = 0xff; /* Initiate data transmision */ |
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return 0; |
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} |
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ISR(SIG_SPI) |
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{ |
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//usb_puts("Interrupt");
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/* only handle intterupt when we are expecting data */
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if(spi_bytes > 0){ |
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/* process byte */
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spi_recv_func(SPDR); |
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/* if we've read all the bytes, set SS high to end transmission,
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* otherwise get the next byte */
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if(--spi_bytes == 0){ |
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//usb_puts("Read all bytes\r\n");
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PORTB |= SS; |
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if(spi_recv_complete_func)
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spi_recv_complete_func(); |
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}else {
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//usb_puts("There are this many bytes left: "); usb_puti(spi_bytes);usb_puts("\r\n");
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SPDR = 0xff;
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} |
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} |
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} |