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Altera_Forum's avatar
Altera_Forum
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20 years ago

UART Core with CTS/RTS

In a working design I configured my UART core so that it uses CTS/RTS.

But I do not get a simple design running that shall only send integers from a Windws hyperterminal to via the Nios core and back to the hyperterminal.

I have double-checked that the CTS/RTS-pins are connected as stated in the Stratix II development board, which I am using. Also I have the same baud rate (115200). On the hyperterminal I have selected "Flow Control: Hardware". However, nothing happens.

Can somebody help?

Below is the code of my program, which works without CTS/RTS - Hardware Flow Control.

# include <stdio.h># include "system.h"# include "alt_types.h"# include <time.h># include <sys/alt_timestamp.h>

int main()

{

int x;

FILE* infile;

FILE* outfile;

infile = fopen("/dev/uart1", "r");

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

printf("System ready!\n");

fprintf(outfile, "System ready!\n\r");

while(1)

{

// fprintf(outfile,"New Number: ");

if (fscanf(infile, "%d", &x))

{

fprintf(outfile, "Received: %d\r\n", x);

printf("Received: %d\r\n", x);

}

}

return 0;

}

10 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    20 years ago

    One deviec shall not be open twice before it was closed.

    Maybe,

    io_file = fopen("/dev/uart1", "rw");

    ....

    I just reply it without confirming anything, so please look up some DATASHEET.
  • Altera_Forum's avatar
    Altera_Forum
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    20 years ago

    use a terminal program (e.g. BRAY&#39;s TERMINAL) where you can switch on/off

    RTS and where you can see the state of CTS.

    see file altera_avalon_uart_regs.h

    you can check CTS at nios side with...

    uartstatus=IORD_ALTERA_AVALON_UART_STATUS(UART_1_BASE);

    if(uartstatus&ALTERA_AVALON_UART_STATUS_CTS_MSK) {

    ... // cts is set (low)

    }

    you can set RTS with ...

    ctrl=IORD_ALTERA_AVALON_UART_CONTROL(UART_1_BASE);

    ctrl|=ALTERA_AVALON_UART_CONTROL_RTS_MSK;

    // ctrl&=~ALTERA_AVALON_UART_CONTROL_RTS_MSK; // to clear

    IOWR_ALTERA_AVALON_UART_CONTROL(UART_1_BASE,ctrl)

    if CTS is not set, the fast driver will not send any byte,

    RTS is ignored by the driver, you have to handle it by yourself.
  • Altera_Forum's avatar
    Altera_Forum
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    20 years ago

    Sorry there was something wrong in my last answer,

    the commands to set/reset RTS conflict with the fast

    driver of the uart.

    After checking the documetation,

    There is no information how RTS and CTS is used by the HAL !

    There is no description, which flags of the termios structure

    are supported.

    How can I set/reset RTS from application ???
  • Altera_Forum's avatar
    Altera_Forum
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    20 years ago

    Anyway Fischer,

    thanks for your reply that helped me to find Bray&#39;s terminal. At least I no now that my NiosCore works with "clean" CTS/RTS mode.

    But in many applications (hyperterminal, matlab) there is the option "FlowControl = Hardware" and this seems not to be clean CTS/RTS, because the communication is simply dying...

    Alchemist

    P.S: It seems, Altera tries to hide "unimportant details" from the user. However, sometimes some of these details are needed...
  • Altera_Forum's avatar
    Altera_Forum
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    20 years ago

    I learned a new term reading this post so now I&#39;m curious..... what is "clean" CTS/RTS mode? (I know flow control but what do you mean by "clean"???). By clean if you mean a clean signal ........ RS232 has never been known to be "clean".

  • Altera_Forum's avatar
    Altera_Forum
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    20 years ago

    make sure you set the tx fifo in the com port properties to 1. Do this through control panel - system - device manager.

    This is because, when it&#39;s more than 1 (typically 14/16), the PC continues to send data after you raise CTS. It continues until its FIFO is emptied. Thus you would experience Rx overruns on your embedded device.
  • Altera_Forum's avatar
    Altera_Forum
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    20 years ago

    --- Quote Start ---

    originally posted by badomen@Jun 23 2005, 11:12 AM

    i learned a new term reading this post so now i&#39;m curious..... what is "clean" cts/rts mode? (i know flow control but what do you mean by "clean"???). by clean if you mean a clean signal ........ rs232 has never been known to be "clean".

    --- Quote End ---

    Hej BadOmen,

    with "clean" I meant that only the CTS/RTS and TxD and RxD are used. It is maybe a strange and unofficial term, but since i now have problems with tools like "Hyperterminal" and also "Matlab", where you just specify "FlowControl = Hardware" and do not really know, which pins take part in the communication, I think the term is justified... (When assigning CTS/RTS in a more advanced terminal program, the communication works).

    By the way, maybe someone has a experiences with Matlab and CTS/RTS-communication with Nios. I read the Matlab documentation, but did not get it working.

    Here are my matlab commands (but I tried other as well):

    >> s2 = serial(&#39;COM2&#39;);

    >> set(s2, &#39;BaudRate&#39;, 115200);

    >> set(s2, &#39;FlowControl&#39;, &#39;hardware&#39;);

    >> set(s2, &#39;DataTerminalReady&#39;, &#39;off&#39;);

    >> fopen(s2)

    >> fprintf(s2, &#39;%d&#39;, 3);

    Matlab "freezes" after execution of these commands...

    So, if somebody has a good idea, it would be great...
  • Altera_Forum's avatar
    Altera_Forum
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    19 years ago

    Ok I find THE solution: RST/CTS flow control works well. This my code:

    int main()

    {

    char* msg = "Detected the character &#39;t&#39;.\n";

    FILE* fp;

    char prompt = 0;

    fp = fopen("/dev/uart", "r+");

    unsigned int uart_status;

    unsigned int uart_ctrl;

    if(fp)

    {

    while(prompt != &#39;v&#39;)

    {

    prompt = getc(fp);

    if(prompt == &#39;t&#39;)

    {

    fwrite(msg, strlen(msg), 1, fp);

    }

    }

    fprintf(fp, "Closing the UART file.\n");

    fclose(fp);

    }

    return(0);

    }

    This code works under Hyper Terminal with "hardware" flow control.

    I found the error. It iwas an Altera error.

    You just have to change :

    CTS: PIN L15 (instead of PIN K15)

    RTS: PIN K15 (instead of PIN L15)

    for the Altera DSP Stratix II Evaluation Board.
  • Altera_Forum's avatar
    Altera_Forum
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    11 years ago

    In your code, what do you mean by "&#39" ?

    and how are you checking for an incoming RTS and setting ur own RTS(sending CTS) signal?