common/serial.c

   1 #include <avr/interrupt.h>
   2 #include <avr/io.h>
   3 #include "ringbuffer.h"
   4 #include "serial.h"
   5
   6 #define BIT(n) (1<<(n))
   7
   8 #ifndef SERIAL_BUFSIZE
   9 #define SERIAL_BUFSIZE 16
  10 #endif
  11
  12 #ifdef SERIAL_ASYNC
  13 static RINGBUFFER(rx, SERIAL_BUFSIZE);
  14 static RINGBUFFER(tx, SERIAL_BUFSIZE);
  15 static uint8_t rx_overrun;
  16 #define INTERRUPTS BIT(RXCIE0)
  17 #else
  18 #define INTERRUPTS 0
  19 #endif
  20
  21 void serial_init(uint16_t baud)
  22 {
  23         DDRD = (DDRD&~0x03) | 0x02;
  24         PORTD &= ~0x03;
  25
  26         baud = (F_CPU/16+baud/2)/baud-1;
  27         UBRR0H = baud>>8;
  28         UBRR0L = baud;
  29         UCSR0A = 0;
  30         UCSR0C = BIT(UCSZ00) | BIT(UCSZ01);  // 8N1
  31         UCSR0B = BIT(RXEN0) | BIT(TXEN0) | INTERRUPTS;
  32 }
  33
  34 uint8_t serial_read()
  35 {
  36 #ifdef SERIAL_ASYNC
  37         return ringbuffer_blocking_pop(rx);
  38 #else
  39         while(!(UCSR0A&BIT(RXC0))) ;
  40         return UDR0;
  41 #endif
  42 }
  43
  44 uint8_t serial_read_available()
  45 {
  46 #ifdef SERIAL_ASYNC
  47         return ringbuffer_fill(rx);
  48 #else
  49         return (UCSR0A&BIT(RXC0))!=0;
  50 #endif
  51 }
  52
  53 uint8_t serial_read_overrun()
  54 {
  55 #ifdef SERIAL_ASYNC
  56         uint8_t o = rx_overrun;
  57         rx_overrun = 0;
  58         return o;
  59 #else
  60         return (UCSR0A&BIT(DOR0))!=0;
  61 #endif
  62 }
  63
  64 void serial_write(uint8_t c)
  65 {
  66 #ifdef SERIAL_ASYNC
  67         ringbuffer_blocking_push(tx, c);
  68         UCSR0B |= BIT(UDRIE0);
  69 #else
  70         while(!(UCSR0A&BIT(UDRE0))) ;
  71         UDR0 = c;
  72 #endif
  73 }
  74
  75 uint8_t serial_write_space()
  76 {
  77 #ifdef SERIAL_ASYNC
  78         return ringbuffer_space(tx);
  79 #else
  80         return (UCSR0A&BIT(UDRE0))!=0;
  81 #endif
  82 }
  83
  84 #ifdef SERIAL_ASYNC
  85 ISR(USART_UDRE_vect)
  86 {
  87         if(ringbuffer_fill(tx))
  88                 UDR0 = ringbuffer_pop(tx);
  89         else
  90                 UCSR0B &= ~BIT(UDRIE0);
  91 }
  92
  93 ISR(USART_RX_vect)
  94 {
  95         uint8_t c = UDR0;
  96         if(!ringbuffer_space(rx))
  97                 rx_overrun = 1;
  98         else
  99                 ringbuffer_push(rx, c);
 100 }
 101 #endif