uart/uart.c

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Log
Revision 1.5 2008/01/31 09:38:15 haraldkipp Added return statement in main to avoid warnings with latest GCC.

Revision 1.4 2005/11/22 09:14:13 haraldkipp Replaced specific device names by generalized macros.

Revision 1.3 2004/11/24 16:35:56 haraldkipp Configurable floating point support

Revision 1.2 2004/09/10 10:33:28 haraldkipp Temporarly removed non-configurable FP support

Revision 1.1 2003/08/05 18:59:52 haraldkipp Release 3.3 update

Revision 1.3 2003/02/04 18:19:41 harald Version 3 released

Revision 1.2 2003/02/04 16:24:38 harald Adapted to version 3

Revision 1.1 2002/08/09 12:44:10 harald Renamed for make rules

Revision 1.5 2002/06/12 11:00:10 harald *** empty log message ***

Revision 1.4 2002/06/04 19:13:21 harald *** empty log message ***

Revision 1.3 2002/05/08 16:02:34 harald First Imagecraft compilation

Revision 1.2 2001/08/10 18:20:41 harald GCC version 3 update

Revision 1.1 2001/06/28 18:43:13 harald Preview release

This sample demonstrates the usage of the ATmega on-chip UART. Note, that we don't do any error checking, because without this UART we can't tell the user our problem.

We use floating points. Make sure to link with nutlibcrtf.

00001 
00086 #include <cfg/crt.h>    /* Floating point configuration. */
00087 
00088 #include <string.h>
00089 #include <stdio.h>
00090 #include <io.h>
00091 
00092 #include <dev/board.h>
00093 #include <sys/timer.h>
00094 
00095 static char *banner = "\nNut/OS UART Sample\n";
00096 static prog_char presskey_P[] = "Press any key...";
00097 static prog_char pgm_ptr[] = "\nHello stranger!\n";
00098 
00099 static char inbuf[128];
00100 
00101 /*
00102  * UART sample.
00103  *
00104  * Some functions do not work with ICCAVR.
00105  */
00106 int main(void)
00107 {
00108     int got;
00109     int i;
00110     char *cp;
00111     u_long baud = 115200;
00112     FILE *uart;
00113 #ifdef STDIO_FLOATING_POINT
00114     float dval = 0.0;
00115 #endif
00116 
00117     /*
00118      * Each device must be registered. We do this by referencing the 
00119      * device structure of the driver. The advantage is, that only 
00120      * those device drivers are included in our flash code, which we 
00121      * really need.
00122      *
00123      * The uart0 device is the first one on the ATmega chip. So it 
00124      * has no configurable base address or interrupt and we set both 
00125      * parameters to zero.
00126      */
00127     NutRegisterDevice(&DEV_UART, 0, 0);
00128 
00129     /*
00130      * Now, as the device is registered, we can open it. The fopen()
00131      * function returns a pointer to a FILE structure, which we use 
00132      * for subsequent reading and writing.
00133      */
00134     uart = fopen(DEV_UART_NAME, "r+");
00135 
00136     /*
00137      * Before doing the first read or write, we set the baudrate.
00138      * This low level function doesn't know about FILE structures
00139      * and we use _fileno() to get the low level file descriptor
00140      * of the stream.
00141      *
00142      * The short sleep allows the UART to settle after the baudrate
00143      * change.
00144      */
00145     _ioctl(_fileno(uart), UART_SETSPEED, &baud);
00146 
00147     /*
00148      * Stream devices can use low level read and write functions. 
00149      * Writing program space data is supported too.
00150      */
00151     _write(_fileno(uart), banner, strlen(banner));
00152     {
00153         _write_P(_fileno(uart), presskey_P, sizeof(presskey_P));
00154     }
00155 
00156     /*
00157      * Stream devices do buffered I/O. That means, nothing will be 
00158      * passed to the hardware device until either the output buffer 
00159      * is full or we do a flush. With stream I/O we typically use
00160      * fflush(), but low level writing a null pointer will also flush 
00161      * the output buffer.
00162      */
00163     _write(_fileno(uart), 0, 0);
00164 
00165     /*
00166      * The low level function read() will grab all available bytes 
00167      * from the input buffer. If the buffer is empty, the call will
00168      * block until something is available for reading.
00169      */
00170     got = _read(_fileno(uart), inbuf, sizeof(inbuf));
00171     _write(_fileno(uart), inbuf, got);
00172 
00173     /*
00174      * Nut/OS never expects a thread to return. So we enter an 
00175      * endless loop here.
00176      */
00177     for (i = 0;; i++) {
00178         /*
00179          * A bit more advanced input routine is able to read a string 
00180          * up to and including the first newline character or until a
00181          * specified maximum number of characters, whichever comes first.
00182          */
00183         fputs("\nEnter your name: ", uart);
00184         fflush(uart);
00185         fgets(inbuf, sizeof(inbuf), uart);
00186 
00187         /*
00188          * Chop off trailing linefeed.
00189          */
00190         cp = strchr(inbuf, '\n');
00191         if (cp)
00192             *cp = 0;
00193 
00194         /*
00195          * Streams support formatted output as well as printing strings 
00196          * from program space.
00197          */
00198         if (inbuf[0])
00199             fprintf(uart, "\nHello %s!\n", inbuf);
00200         else {
00201             fputs_P(pgm_ptr, uart);
00202         }
00203 
00204         /*
00205          * Just to demonstrate formatted floating point output.
00206          * In order to use this, we need to link the application
00207          * with nutcrtf instead of nutcrt for pure integer.
00208          */
00209 #ifdef STDIO_FLOATING_POINT
00210         dval += 1.0125;
00211         fprintf(uart, "FP %f\n", dval);
00212 #endif
00213     }
00214     return 0;
00215 }

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