common/serial.c

   1 #include <avr/interrupt.h>
   2 #include <avr/io.h>
   3 #include "delay.h"
   4 #include "ringbuffer.h"
   5 #include "serial.h"
   6
   7 #define BIT(n) (1<<(n))
   8
   9 #ifndef SERIAL_BUFSIZE
  10 #define SERIAL_BUFSIZE 16
  11 #endif
  12
  13 #ifdef SERIAL_ASYNC
  14 static RINGBUFFER(rx, SERIAL_BUFSIZE);
  15 static RINGBUFFER(tx, SERIAL_BUFSIZE);
  16 static uint8_t rx_overrun;
  17 #define INTERRUPTS BIT(RXCIE0)
  18 #else
  19 #define INTERRUPTS 0
  20 #endif
  21
  22 static inline void set_baud(uint16_t baud)
  23 {
  24         baud = (F_CPU/16+baud/2)/baud-1;
  25         UBRR0H = baud>>8;
  26         UBRR0L = baud;
  27 }
  28
  29 void serial_init(uint16_t baud)
  30 {
  31         DDRD = (DDRD&~0x03) | 0x02;
  32         PORTD &= ~0x03;
  33
  34         set_baud(baud);
  35         UCSR0A = 0;
  36         UCSR0C = BIT(UCSZ00) | BIT(UCSZ01);  // 8N1
  37         UCSR0B = BIT(RXEN0) | BIT(TXEN0) | INTERRUPTS;
  38 }
  39
  40 void serial_set_baud(uint16_t baud)
  41 {
  42 #ifdef SERIAL_ASYNC
  43         while(!(UCSR0A&BIT(UDRE0))) ;
  44 #endif
  45         /* It's impossible to reliably find out when transmission has finished.
  46         Wait for one character duration to be safe. */
  47         uint16_t delay = (UBRR0H<<8)|UBRR0L;
  48         for(uint8_t i=0; i<40; ++i)
  49                 delay_loop16(delay);
  50         set_baud(baud);
  51 }
  52
  53 uint8_t serial_read()
  54 {
  55 #ifdef SERIAL_ASYNC
  56         return ringbuffer_blocking_pop(rx);
  57 #else
  58         while(!(UCSR0A&BIT(RXC0))) ;
  59         return UDR0;
  60 #endif
  61 }
  62
  63 uint8_t serial_read_available()
  64 {
  65 #ifdef SERIAL_ASYNC
  66         return ringbuffer_fill(rx);
  67 #else
  68         return (UCSR0A&BIT(RXC0))!=0;
  69 #endif
  70 }
  71
  72 uint8_t serial_read_overrun()
  73 {
  74 #ifdef SERIAL_ASYNC
  75         uint8_t o = rx_overrun;
  76         rx_overrun = 0;
  77         return o;
  78 #else
  79         return (UCSR0A&BIT(DOR0))!=0;
  80 #endif
  81 }
  82
  83 void serial_write(uint8_t c)
  84 {
  85 #ifdef SERIAL_ASYNC
  86         ringbuffer_blocking_push(tx, c);
  87         UCSR0B |= BIT(UDRIE0);
  88 #else
  89         while(!(UCSR0A&BIT(UDRE0))) ;
  90         UDR0 = c;
  91 #endif
  92 }
  93
  94 uint8_t serial_write_space()
  95 {
  96 #ifdef SERIAL_ASYNC
  97         return ringbuffer_space(tx);
  98 #else
  99         return (UCSR0A&BIT(UDRE0))!=0;
 100 #endif
 101 }
 102
 103 #ifdef SERIAL_ASYNC
 104 ISR(USART_UDRE_vect)
 105 {
 106         if(ringbuffer_fill(tx))
 107                 UDR0 = ringbuffer_pop(tx);
 108         else
 109                 UCSR0B &= ~BIT(UDRIE0);
 110 }
 111
 112 ISR(USART_RX_vect)
 113 {
 114         uint8_t c = UDR0;
 115         if(!ringbuffer_space(rx))
 116                 rx_overrun = 1;
 117         else
 118                 ringbuffer_push(rx, c);
 119 }
 120 #endif