UART Core with CTS/RTS

[Altera_Forum]

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; }

[Altera_Forum]

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]

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]

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]

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]

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]

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]

--- 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]

if you use RTS&CTS Handshake and you set hyperterminal to flowcontrol,  

perhaps it also wants to handle DTR/DSR/CD Signals.  assuming 9 PIN SUB-D at the PC side, make a bridge between PINS 4 -> 6+1, so the PC  sets DATA TERMINAL READY(PIN4) and gets back DATA SET READY(PIN6) + CARRIER DETECT(PIN1)  see also http://www.hardwarebook.net/cable/serial/n...lmodem9to9.html (http://www.hardwarebook.net/cable/serial/nullmodem9to9.html)

[Altera_Forum]

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]

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?