common/spi_io_usi.c

   1 /*
   2 ATtinyX61:
   3 DI -> 0
   4 DO -> 1
   5 CLK-> 2
   6 */
   7
   8 static inline void spi_isr_on (void)  {USICR |= (1<<USIOIE);}
   9 static inline void spi_isr_off(void)  {USICR &= (uint8_t)~(1<<USIOIE);}
  10
  11 static void spi_io_init_hw(void) {
  12   power_usi_enable();
  13
  14         // Clr the flags we interupt on + counter bits in same reg.
  15         //  (default is not raised)
  16      //USISR = (1<<USIOIF);
  17
  18         // Clr datareg to avoid junk data being sent out. (defaults to 0)
  19         //USIDR = 0;
  20
  21         #define B 0
  22         #define A 1
  23
  24         #if ( SPI_PORT == B )
  25         //#warning Using Port  B (default)
  26     //USIPP &= (uint8_t)~(1<<USIPOS);
  27         #else
  28         #error Using Port  A
  29         USIPP |= (1<<USIPOS);
  30   #endif
  31
  32   #undef A
  33         #undef B
  34
  35         DDR(SPI_PORT) |= (1<<SPI_MISO);
  36         DDR(SPI_PORT) &= (uint8_t)~((1<<SPI_MOSI)|(1<<SPI_CLK));
  37         PORT(SPI_PORT)&= (uint8_t)~( (1<<SPI_MOSI) | (1<<SPI_CLK) | (1<<SPI_MISO) );
  38
  39   // To resolve SPI_EDGE
  40   #define NEGATIVE 1
  41   #define POSITIVE 0
  42
  43   USICR = (0<<USISIE) |                 // Start IE(2w), CLK edge IE(3w)
  44           (1<<USIOIE) |                         // Ovf interupt (to refil register)
  45           (0<<USIWM1) | (1<<USIWM0) |   // 01 = 3w, 00 = disable, 10&11 = 2w
  46           (1<<USICS1) | (SPI_EDGE<<USICS0) | // 10 = positive edge, 11 = neg.
  47           (0<<USICLK) |                         // 4bit timer : 0 = external, 1 = sw
  48           (0<<USITC );                          // Clock toggle
  49
  50   #undef NEGATIVE
  51   #undef POSITIVE
  52 }
  53
  54 ISR( SIG_USI_OVERFLOW ) {
  55      USISR = (1<<USIOIF); // Clear interupt flag and counter.
  56
  57         //transmit (tx)
  58      if (!q_empty(&tx)) {
  59                 USIDR = q_pop(&tx);
  60         }
  61         else USIDR = 0;
  62
  63      //recieve (rx)
  64         uint8_t in = USIBR;
  65      if (in != 0 && !q_full(&rx)) {
  66           q_push(&rx,in);
  67                 if (in == '\n')
  68                         spi_io_rx_nl++;
  69      }
  70
  71         /*// Alternate if we don't care about losing old data.
  72         if (USIBR != 0) {
  73           q_push_o(&rx,USIBR);
  74      }
  75         */
  76 }