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Altera_Forum's avatar
Altera_Forum
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21 years ago

Read from UART

Good morning!

I´m a NIOSII starter and trying to get first results.

My question: Why can´t i read anything from the UART? I can write to it, but i don´t receive anything or i receive and don´t recognize it.

I´m working with WIN2000, a DSP 1S25-Board, Quartus II 4.2, NIOSII 1.1.

Because of tutorials i suppose that "normal" C should work with NIOSII (this is a fragment of the SW-Tutorial for writing to the UART and it works:

// fp = fopen ("/dev/uart1", "w");

// if (fp)

// {

// fprintf(fp, "%s",msg);

// }

// fclose (fp);

Now i want to read from it:

// TRY TO READ FROM UART1

// input = NULL;

// input = fopen ("/dev/uart1", "r+");

// if (input)

// {

// printf("%c",fgetc(input));

// }

// fclose(input);

// input = NULL;

But there is no reaction http://forum.niosforum.com/work2/style_emoticons/<#EMO_DIR#>/huh.gif !?

I am thankful for any ideas and please respect my beginner-status...

Nice day! Max

11 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    21 years ago

    I have the sam problem.I think it is a bug niosII.only can transfer data to pc,but I can&#39;t

    receive data from pc.

    I want The altera can give me a definite explaination!!!
  • Altera_Forum's avatar
    Altera_Forum
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    21 years ago

    Hi guys,

    Make sure that the baud rate of the PC serial port and the port on the fpga is the same. the same goes for the stop bits, parity and data bits

    We experienced data corruption at the standard speed (115200) over here, when using the serial cable that was supplied with our stratix II kit. So we lowered the speed to a save 9600

    I successfully use here:

    Baud: 9600

    Databits: 8

    Stopbit: 1:

    Parity: None

    Flowcontrol: none

    The speed of the port on the board can be set in the SOPC builder by doublicking on the UART item. You can choose to make it reconfigurable at runtime, but I haven&#39;t used that yet.

    Good luck!

    Jos
  • Altera_Forum's avatar
    Altera_Forum
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    21 years ago

    And another thing, there seems to be something strange going on with the character read functions. In the "board diagnostics" sample program that comes with the NIOS II IDE, somewhere in the code, you will find:

    /* This extra getchar() to work around an Eclipse feature */

    getchar();

    ch = getchar();

    I have no idea why this is an eclipse feature and not a nios Bug, but anyway... http://forum.niosforum.com/work2/style_emoticons/<#EMO_DIR#>/blink.gif

    Maybe this is part of your problem?
  • Altera_Forum's avatar
    Altera_Forum
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    21 years ago

    Thanks for your help!

    I modified my UART in SOPC-Builder, now it has the same properties (i took the values of jmastron) as my Hyperterminal (is there a better alternative?). Also i modified my source code , i took Fischers code example in the other thread about nonblocking stdin as base:

    int fdterm; // FILEDESCRIPTOR RETURNED BY OPEN

    FILE * fpterm; // FILE pointer returned by fdopen

    int uart1_rxcount = 0;

    char uart1_rxbuffer[255];

    int main()

    {

    fdterm = open("/dev/uart1", O_RDWR | O_NONBLOCK | O_NOCTTY);

    fpterm = fdopen(fdterm,"rw+");

    uart1_rxcount=read(fdterm, &uart1_rxbuffer, sizeof(uart1_rxbuffer));

    if(uart1_rxcount>0)

    {

    fprintf(fpterm,"received:%s\r\n",uart1_rxbuffer);

    }

    Now: my debugger says uart1_rxcount is always NULL http://forum.niosforum.com/work2/style_emoticons/<#EMO_DIR#>/dry.gif , still nothing happens... Do i have to implement interrupts from the uart? And whats about this EPP port Jeroen was talking about?

    Anyway, it´s funny to see that something happens with my board http://forum.niosforum.com/work2/style_emoticons/<#EMO_DIR#>/biggrin.gif

    Hope to hear you...

    Max
  • Altera_Forum's avatar
    Altera_Forum
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    21 years ago

    do you use a while(1) around read ???

    you don&#39;t need an interrupt, this is always done in the HAL driver altera_avalon_uart.c

    I don`t know if this is necessary, but set stdin,stdout,stderr in syslib properties to null or something other than

    uart1.

    int main()

    {

    fdterm = open("/dev/uart1", O_RDWR | O_NONBLOCK | O_NOCTTY);

    fpterm = fdopen(fdterm,"rw+");

    fprintf(fpterm,"UART1 STARTED\r\n"); // check initial output

    while(1) {

    uart1_rxcount=read(fdterm, &uart1_rxbuffer, sizeof(uart1_rxbuffer));

    if(uart1_rxcount>0) { {

    fprintf(fpterm,"received:%s\r\n",uart1_rxbuffer);

    }

    }

    }
  • Altera_Forum's avatar
    Altera_Forum
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    21 years ago

    This is great stuff guys, I&#39;m trying to do something similar. I have one question: What headers do I need to include? The Software developers guide says to include <unistd.h> but I get compile errors saying that the compiler doesn&#39;t know what open or O_NONBLOCK is. Thanks

  • Altera_Forum's avatar
    Altera_Forum
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    21 years ago

    i use these:

    # include <stdio.h># include <stddef.h># include <string.h># include <fcntl.h># include <unistd.h># include "system.h"# include "sys/alt_alarm.h"# include "alt_types.h"# include "altera_avalon_pio_regs.h"# include "sys/alt_irq.h"# include "altera_avalon_uart.h"

    don´t think you need all of them, but my programs runs...

    no idea about NIOSI http://forum.niosforum.com/work2/style_emoticons/<#EMO_DIR#>/sad.gif