root / trunk / code / projects / libdragonfly / spi.c @ 1926
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1 | 868 | justin | /**
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2 | * @file spi.c
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3 | * @brief Basic SPI module to handle encoders
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4 | * @author Colony Project, CMU Robotics Club
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5 | * Need to move spi.h include into dragonfly_lib.h when stable
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6 | **/
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7 | |||
8 | #include <avr/interrupt.h> |
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9 | #include "spi.h" |
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10 | |||
11 | |||
12 | static volatile char spi_bytes; /* number of bytes to read */ |
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13 | static spi_fun_recv_t spi_recv_func; /* byte handler */ |
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14 | static spi_fun_recv_complete_t spi_recv_complete_func; /*transmission completion handler */ |
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15 | |||
16 | /**
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17 | * @brief Initialize SPI hardware for communication.
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18 | *
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19 | * @param recv_func The function to be called for each byte of data received.
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20 | * @param recv_complete_func The function to be called at the end of a complete transmission.
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21 | */
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22 | 1496 | jsexton | void spi_init (spi_fun_recv_t recv_func, spi_fun_recv_complete_t recv_complete_func)
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23 | 868 | justin | { |
24 | /* Enable Interrupt, Enable SPI Module, MSB First, Master Mode, Clock div = 64 */
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25 | SPCR = _BV(SPE) | _BV(SPIE) /*| _BV(DORD)*/ | _BV(MSTR) | _BV(SPR1) | _BV(SPR0);
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26 | SPSR = _BV(SPI2X); |
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27 | |||
28 | /* Set SCLK, SS, MOSI as outputs. MISO as input */
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29 | DDRB |= MOSI | SCLK | SS; |
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30 | DDRB &= ~MISO; |
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31 | |||
32 | /* Keep SS high until transmit */
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33 | PORTB |= SS; |
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34 | |||
35 | /* set function to be executed when we receive a byte */
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36 | spi_recv_func = recv_func; |
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37 | spi_recv_complete_func = recv_complete_func; |
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38 | spi_bytes = 0;
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39 | //usb_puts("\tspi.c Debug: SPI INITIALIZED\n");
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40 | } |
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41 | |||
42 | /**
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43 | * @brief Transfer a given byte to slave and receive a byte
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44 | *
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45 | * @param bytes The number of bytes to be transferred.
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46 | **/
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47 | 1496 | jsexton | void spi_transfer(char bytes) |
48 | 868 | justin | { |
49 | spi_bytes = bytes; |
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50 | PORTB &= ~SS; /* Set SS low to initiate transmission */
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51 | SPDR = 0xff; /* Initiate data transmision */ |
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52 | } |
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53 | |||
54 | ISR(SIG_SPI) |
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55 | { |
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56 | //usb_puts("Interrupt");
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57 | /* only handle intterupt when we are expecting data */
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58 | if(spi_bytes > 0){ |
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59 | /* process byte */
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60 | spi_recv_func(SPDR); |
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61 | /* if we've read all the bytes, set SS high to end transmission,
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62 | * otherwise get the next byte */
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63 | if(--spi_bytes == 0){ |
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64 | //usb_puts("Read all bytes\r\n");
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65 | PORTB |= SS; |
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66 | if(spi_recv_complete_func)
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67 | spi_recv_complete_func(); |
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68 | }else {
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69 | //usb_puts("There are this many bytes left: "); usb_puti(spi_bytes);usb_puts("\r\n");
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70 | SPDR = 0xff;
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71 | } |
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72 | } |
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73 | } |