serial.c

   1 #include "brmpuk.h"
   2
   3 #include <avr/io.h>
   4 #include <avr/interrupt.h>
   5 #include "serial.h"
   6
   7
   8 #define NOINT
   9 #ifndef NOINT
  10
  11 /* Ring buffer for received data. */
  12
  13 #define BUF_SIZE 64
  14
  15 struct ring_buffer {
  16         /* ........incoming.......
  17          *         ^head   ^head+bytes */
  18         unsigned char buffer[BUF_SIZE];
  19         int head;
  20         int bytes;
  21 } buf = { { 0 }, 0, 0 };
  22
  23 static inline void store_char(uint8_t data)
  24 {
  25         if (buf.bytes >= BUF_SIZE)
  26                 return; // overflow!
  27
  28         int i = (buf.head + buf.bytes) % BUF_SIZE;
  29         buf.buffer[i] = data;
  30         buf.bytes++;
  31 }
  32
  33 #endif
  34
  35
  36 /* USART hardware handling. */
  37
  38 #define BAUD 38400  // Rychlost prenosu dat
  39 #define MYUBRR (F_CPU/16/BAUD-1) // Konstanta pouzita pro nastaveni prenosu
  40
  41 static void USART0_Init(uint16_t ubrr) { // fukce pro inicializaci USART0 komunikace
  42         UBRR0H = (uint8_t) (ubrr >> 8);
  43         UBRR0L = (uint8_t) ubrr;
  44
  45         UCSR0C = (1<<UCSZ01)|(1<<UCSZ00) | (1<<UPM01)|(1<<UPM00)/* | (1<<USBS0)*/; // 8 N 1
  46         UCSR0A = 0; // no special stuff
  47
  48         UCSR0B = (1<<RXEN0)|(1<<TXEN0)
  49 #ifndef NOINT
  50                 | (1<<RXCIE0)
  51 #endif
  52                 ;
  53 }
  54
  55 static void USART0_Transmit(uint8_t data) { // poslani dat po USART0
  56         while (!(UCSR0A & (1<<UDRE0))) ; // cekani na odesilaci buffer
  57         UDR0 = data; // zapsani dat = odeslani dat po USART0
  58 }
  59
  60 #ifndef NOINT
  61 SIGNAL(SIG_UART0_RECV)
  62 {
  63         unsigned char data = UDR0;
  64         store_char(data);
  65         if (data >= 'A' && data <= 'Z')
  66                 data ^= 0x20;
  67         USART0_Transmit(data);
  68 }
  69 #endif
  70
  71
  72 /* Public API. */
  73
  74 void serial_init(void)
  75 {
  76         USART0_Init(MYUBRR);
  77 }
  78
  79 void serial_send(uint8_t data)
  80 {
  81         USART0_Transmit(data);
  82 }
  83
  84 int serial_waiting(void)
  85 {
  86 #ifdef NOINT
  87         return UCSR0A & _BV(RXC0);
  88 #else
  89         return buf.bytes;
  90 #endif
  91 }
  92
  93 uint8_t serial_recv(void)
  94 {
  95 #ifdef NOINT
  96         volatile int x = 0;
  97         while (!serial_waiting()) x++;
  98
  99         uint8_t data = UDR0;
 100 #if 0
 101         if (data >= 'A' && data <= 'Z')
 102                 data ^= 0x20;
 103         USART0_Transmit(data);
 104 #endif
 105         return data;
 106 #else
 107         // cli-sti is actually not required, this is race-free!
 108         uint8_t data = buf.buffer[buf.head];
 109         buf.bytes--;
 110         buf.head = (buf.head + 1) % BUF_SIZE;
 111         return data;
 112 #endif
 113 }