Linux/PROCESSOR-SDK-AM335X: UART custom baud rate

Karthikeyan R

Tool/software: Linux

Hi ,

I m facing issue , while setting my custom baud rates

root@sfms:~# stty -F /dev/ttyS4 1200
root@sfms:~# stty -F /dev/ttyS4 10400
stty: invalid argument '10400'
root@sfms:~# stty -F /dev/ttyS4 10965
stty: invalid argument '10965'

I referred the below TI link


In that, you are requesting to set baud for particular UART port through system call as 38400 then it will set it to 10400.
Then what is the baud rate for 10965 ? How to calculate it ?  Is it possible directly set the custom baud rate ?

https://e2e.ti.com/support/arm/sitara_arm/f/791/p/384844/1357293#pi316653filter=all&pi316653scroll=false

over 8 years ago

0 Biser Gatchev-XID over 8 years ago

TI__Guru**** 393215 points

The software team have been notified. They will respond here.

0 Karthikeyan R over 8 years ago in reply to Biser Gatchev-XID

Expert 1410 points

Yeah , thanks for the reply Biser

0 Cvetolin Shulev-XID over 8 years ago in reply to Karthikeyan R

TI__Guru 65405 points

Karthikeyan,

I think the problem is that the uart driver do not allow to change to a custom baudrate. You can try to modify the driver.

An other opportunity is to make your own application and define custom baudrate as it is described below:

#include <stropts.h>
#include <asm/termios.h>
.....

struct termios2 tio;

ioctl(fd, TCGETS2, &tio);
tio.c_cflag &= ~CBAUD;
tio.c_cflag |= BOTHER;
tio.c_ispeed = 12345;
tio.c_ospeed = 12345;
ioctl(fd, TCSETS2, &tio);

Tsvetolin Shulev

0 Karthikeyan R over 8 years ago in reply to Cvetolin Shulev-XID

Expert 1410 points

Hi Cvetolin,

Thanks for the reply. I proceed with application method

0 Karthikeyan R over 8 years ago in reply to Karthikeyan R

Expert 1410 points

Hi Cvetolin,

I configured the serial port using API.

The output of the ospeed and ispeed got changed according to my configuration.

But I m not getting the proper data for 10400 Baud Rate.
Can able to receive proper data on 1200 Baud Rate.

What might be the problem in the API method configuration?

0 Karthikeyan R over 8 years ago in reply to Karthikeyan R

Expert 1410 points

Here my API,

int8_t klineConfigPort(uint64_t baudrate)
{
   struct termios2 options;
   int ret, fd;

   /* Open Kline uart connection */
   if((baudrate < 0) || (baudrate > MAX_BAUDRATE)) {
       FMS_LOG(LOG_ERR,"Wrong baudrate[0-460800]:%d\r\n", baudrate);
       return -1;
   }

   /* Open Kline uart connection */
   fd = open(KLINE_DEV, O_RDWR | O_NOCTTY);
   if(fd < 0) {
       FMS_LOG(LOG_ERR,"Error opening %s \r\n", KLINE_DEV);
       return -1;
   }

   /* Get serial port parameters */
   ret = ioctl(fd, TCGETS2, &options);
   if(ret !=0) {
       FMS_LOG(LOG_ERR,"Error getting kline uart parameters\r\n");
       return -1;
   }

   FMS_LOG(LOG_DEBUG,"Current baudrate (i/o): %d/%d\n",
       options.c_ispeed, options.c_ospeed);

   /* Set the baud rate */
   options.c_cflag &= ~CBAUD;
   options.c_cflag |= BOTHER;
   options.c_ispeed = baudrate;
   options.c_ospeed = baudrate;

   /* Enable the receiver and set local mode */
   options.c_cflag |= (CLOCAL | CREAD);

   /* No parity (8N1) */
   options.c_cflag &= ~PARENB;
   options.c_cflag &= ~CSTOPB;
   options.c_cflag &= ~CSIZE;
   options.c_cflag |= CS8;

   /* Disbale hardware flow control (CNEW_RTCCTS) */
   /* N7 extension */
   options.c_cflag &= ~CRTSCTS;

   /* N7 fix, disable XON XOFF explicitely */
   options.c_iflag &= ~(INLCR | ICRNL | IGNCR | IXON | IXOFF);
   /* N7 ignore framing and parity errors */
   options.c_iflag |= IGNPAR;

   /* set raw output */
   options.c_oflag &= ~OPOST;
   options.c_oflag &= ~OLCUC;
   options.c_oflag &= ~ONLRET;
   options.c_oflag &= ~ONOCR;
   options.c_oflag &= ~OCRNL;

   /* Set the new options for the port */
   ret = ioctl(fd, TCSETS2, &options);
   if (ret != 0) {
       FMS_LOG(LOG_ERR,"Error setting kline uart parameters\r\n");
       return -1;
   }
   /* Get serial port parameters */
   ret = ioctl(fd, TCGETS2, &options);
   if(ret !=0) {
       FMS_LOG(LOG_ERR,"Error getting uart parameters\r\n");
       return -1;
   }

   FMS_LOG(LOG_DEBUG,"Updated baudrate (i/o): %d/%d\n",
       options.c_ispeed, options.c_ospeed);

   close(fd);
   return 0;
}

Can you tell me what went wrong ?

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Linux/PROCESSOR-SDK-AM335X: UART custom baud rate