uart/uart.c

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Log
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 
00083 #include <cfg/crt.h>    /* Floating point configuration. */
00084 
00085 #include <string.h>
00086 #include <stdio.h>
00087 #include <io.h>
00088 
00089 #include <dev/board.h>
00090 #include <sys/timer.h>
00091 
00092 static char *banner = "\nNut/OS UART Sample\n";
00093 static prog_char presskey_P[] = "Press any key...";
00094 static prog_char pgm_ptr[] = "\nHello stranger!\n";
00095 
00096 static char inbuf[128];
00097 
00098 /*
00099  * UART sample.
00100  *
00101  * Some functions do not work with ICCAVR.
00102  */
00103 int main(void)
00104 {
00105     int got;
00106     int i;
00107     char *cp;
00108     u_long baud = 115200;
00109     FILE *uart;
00110 #ifdef STDIO_FLOATING_POINT
00111     float dval = 0.0;
00112 #endif
00113 
00114     /*
00115      * Each device must be registered. We do this by referencing the 
00116      * device structure of the driver. The advantage is, that only 
00117      * those device drivers are included in our flash code, which we 
00118      * really need.
00119      *
00120      * The uart0 device is the first one on the ATmega chip. So it 
00121      * has no configurable base address or interrupt and we set both 
00122      * parameters to zero.
00123      */
00124     NutRegisterDevice(&DEV_UART, 0, 0);
00125 
00126     /*
00127      * Now, as the device is registered, we can open it. The fopen()
00128      * function returns a pointer to a FILE structure, which we use 
00129      * for subsequent reading and writing.
00130      */
00131     uart = fopen(DEV_UART_NAME, "r+");
00132 
00133     /*
00134      * Before doing the first read or write, we set the baudrate.
00135      * This low level function doesn't know about FILE structures
00136      * and we use _fileno() to get the low level file descriptor
00137      * of the stream.
00138      *
00139      * The short sleep allows the UART to settle after the baudrate
00140      * change.
00141      */
00142     _ioctl(_fileno(uart), UART_SETSPEED, &baud);
00143 
00144     /*
00145      * Stream devices can use low level read and write functions. 
00146      * Writing program space data is supported too.
00147      */
00148     _write(_fileno(uart), banner, strlen(banner));
00149     {
00150         _write_P(_fileno(uart), presskey_P, sizeof(presskey_P));
00151     }
00152 
00153     /*
00154      * Stream devices do buffered I/O. That means, nothing will be 
00155      * passed to the hardware device until either the output buffer 
00156      * is full or we do a flush. With stream I/O we typically use
00157      * fflush(), but low level writing a null pointer will also flush 
00158      * the output buffer.
00159      */
00160     _write(_fileno(uart), 0, 0);
00161 
00162     /*
00163      * The low level function read() will grab all available bytes 
00164      * from the input buffer. If the buffer is empty, the call will
00165      * block until something is available for reading.
00166      */
00167     got = _read(_fileno(uart), inbuf, sizeof(inbuf));
00168     _write(_fileno(uart), inbuf, got);
00169 
00170     /*
00171      * Nut/OS never expects a thread to return. So we enter an 
00172      * endless loop here.
00173      */
00174     for (i = 0;; i++) {
00175         /*
00176          * A bit more advanced input routine is able to read a string 
00177          * up to and including the first newline character or until a
00178          * specified maximum number of characters, whichever comes first.
00179          */
00180         fputs("\nEnter your name: ", uart);
00181         fflush(uart);
00182         fgets(inbuf, sizeof(inbuf), uart);
00183 
00184         /*
00185          * Chop off trailing linefeed.
00186          */
00187         cp = strchr(inbuf, '\n');
00188         if (cp)
00189             *cp = 0;
00190 
00191         /*
00192          * Streams support formatted output as well as printing strings 
00193          * from program space.
00194          */
00195         if (inbuf[0])
00196             fprintf(uart, "\nHello %s!\n", inbuf);
00197         else {
00198             fputs_P(pgm_ptr, uart);
00199         }
00200 
00201         /*
00202          * Just to demonstrate formatted floating point output.
00203          * In order to use this, we need to link the application
00204          * with nutcrtf instead of nutcrt for pure integer.
00205          */
00206 #ifdef STDIO_FLOATING_POINT
00207         dval += 1.0125;
00208         fprintf(uart, "FP %f\n", dval);
00209 #endif
00210     }
00211 }

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