arduino-0018-windows

arduino-0018-windows/hardware/tools/avr/doc/avr-libc/examples/stdiodemo/uart.c

@@ -0,0 +1,186 @@
+/*
+ * ----------------------------------------------------------------------------
+ * "THE BEER-WARE LICENSE" (Revision 42):
+ * <joerg@FreeBSD.ORG> wrote this file.  As long as you retain this notice you
+ * can do whatever you want with this stuff. If we meet some day, and you think
+ * this stuff is worth it, you can buy me a beer in return.        Joerg Wunsch
+ * ----------------------------------------------------------------------------
+ *
+ * Stdio demo, UART implementation
+ *
+ * $Id: uart.c,v 1.1 2005/12/28 21:38:59 joerg_wunsch Exp $
+ */
+
+#include "defines.h"
+
+#include <stdint.h>
+#include <stdio.h>
+
+#include <avr/io.h>
+
+#include "uart.h"
+
+/*
+ * Initialize the UART to 9600 Bd, tx/rx, 8N1.
+ */
+void
+uart_init(void)
+{
+#if F_CPU < 2000000UL && defined(U2X)
+  UCSRA = _BV(U2X);             /* improve baud rate error by using 2x clk */
+  UBRRL = (F_CPU / (8UL * UART_BAUD)) - 1;
+#else
+  UBRRL = (F_CPU / (16UL * UART_BAUD)) - 1;
+#endif
+  UCSRB = _BV(TXEN) | _BV(RXEN); /* tx/rx enable */
+}
+
+/*
+ * Send character c down the UART Tx, wait until tx holding register
+ * is empty.
+ */
+int
+uart_putchar(char c, FILE *stream)
+{
+
+  if (c == '\a')
+    {
+      fputs("*ring*\n", stderr);
+      return 0;
+    }
+
+  if (c == '\n')
+    uart_putchar('\r', stream);
+  loop_until_bit_is_set(UCSRA, UDRE);
+  UDR = c;
+
+  return 0;
+}
+
+/*
+ * Receive a character from the UART Rx.
+ *
+ * This features a simple line-editor that allows to delete and
+ * re-edit the characters entered, until either CR or NL is entered.
+ * Printable characters entered will be echoed using uart_putchar().
+ *
+ * Editing characters:
+ *
+ * . \b (BS) or \177 (DEL) delete the previous character
+ * . ^u kills the entire input buffer
+ * . ^w deletes the previous word
+ * . ^r sends a CR, and then reprints the buffer
+ * . \t will be replaced by a single space
+ *
+ * All other control characters will be ignored.
+ *
+ * The internal line buffer is RX_BUFSIZE (80) characters long, which
+ * includes the terminating \n (but no terminating \0).  If the buffer
+ * is full (i. e., at RX_BUFSIZE-1 characters in order to keep space for
+ * the trailing \n), any further input attempts will send a \a to
+ * uart_putchar() (BEL character), although line editing is still
+ * allowed.
+ *
+ * Input errors while talking to the UART will cause an immediate
+ * return of -1 (error indication).  Notably, this will be caused by a
+ * framing error (e. g. serial line "break" condition), by an input
+ * overrun, and by a parity error (if parity was enabled and automatic
+ * parity recognition is supported by hardware).
+ *
+ * Successive calls to uart_getchar() will be satisfied from the
+ * internal buffer until that buffer is emptied again.
+ */
+int
+uart_getchar(FILE *stream)
+{
+  uint8_t c;
+  char *cp, *cp2;
+  static char b[RX_BUFSIZE];
+  static char *rxp;
+
+  if (rxp == 0)
+    for (cp = b;;)
+      {
+	loop_until_bit_is_set(UCSRA, RXC);
+	if (UCSRA & _BV(FE))
+	  return _FDEV_EOF;
+	if (UCSRA & _BV(DOR))
+	  return _FDEV_ERR;
+	c = UDR;
+	/* behaviour similar to Unix stty ICRNL */
+	if (c == '\r')
+	  c = '\n';
+	if (c == '\n')
+	  {
+	    *cp = c;
+	    uart_putchar(c, stream);
+	    rxp = b;
+	    break;
+	  }
+	else if (c == '\t')
+	  c = ' ';
+
+	if ((c >= (uint8_t)' ' && c <= (uint8_t)'\x7e') ||
+	    c >= (uint8_t)'\xa0')
+	  {
+	    if (cp == b + RX_BUFSIZE - 1)
+	      uart_putchar('\a', stream);
+	    else
+	      {
+		*cp++ = c;
+		uart_putchar(c, stream);
+	      }
+	    continue;
+	  }
+
+	switch (c)
+	  {
+	  case 'c' & 0x1f:
+	    return -1;
+
+	  case '\b':
+	  case '\x7f':
+	    if (cp > b)
+	      {
+		uart_putchar('\b', stream);
+		uart_putchar(' ', stream);
+		uart_putchar('\b', stream);
+		cp--;
+	      }
+	    break;
+
+	  case 'r' & 0x1f:
+	    uart_putchar('\r', stream);
+	    for (cp2 = b; cp2 < cp; cp2++)
+	      uart_putchar(*cp2, stream);
+	    break;
+
+	  case 'u' & 0x1f:
+	    while (cp > b)
+	      {
+		uart_putchar('\b', stream);
+		uart_putchar(' ', stream);
+		uart_putchar('\b', stream);
+		cp--;
+	      }
+	    break;
+
+	  case 'w' & 0x1f:
+	    while (cp > b && cp[-1] != ' ')
+	      {
+		uart_putchar('\b', stream);
+		uart_putchar(' ', stream);
+		uart_putchar('\b', stream);
+		cp--;
+	      }
+	    break;
+	  }
+      }
+
+  c = *rxp++;
+  if (c == '\n')
+    rxp = 0;
+
+  return c;
+}
+