Moxa TC-SW04-M12-4P-T [24/43] Tc sp04 db44 t configuring the baudrate

TC-6000 Series Expansion Modules Software Installation and Programming Guide

4-4

WARNING

If you use

the stty command to get interface stats from a connection configured for a non-standard baudrate

the system will return a rate of 0.

TC-SP04-DB44-T: Configuring the Baudrate

Example Script #1: Setting the Baudrate)

#define MOXA 0x400

#define MOXA_SET_SPECIAL_BAUD_RATE (MOXA+100)

#define MOXA_GET_SPECIAL_BAUD_RATE (MOXA+101)

#include <termios.h>

struct termios term;

int fd, speed;

fd = open(“/dev/ttyM8”, O_RDWR);

tcgetattr(fd, &term);

term.c_cflag &= ~(CBAUD | CBAUDEX);

term.c_cflag |= B4000000;

tcsetattr(fd, TCSANOW, &term);

speed = 115200;

ioctl(fd, MOXA_SET_SPECIAL_BAUD_RATE, &speed);

Example Script #2: Return the Baudrate

#define MOXA 0x400

#define MOXA_SET_SPECIAL_BAUD_RATE (MOXA+100)

#define MOXA_GET_SPECIAL_BAUD_RATE (MOXA+101)

#include <termios.h>

struct termios term;

int fd, speed;

fd = open(“/dev/ttyM8”, O_RDWR);

tcgetattr(fd, &term);

if ( (term.c_cflag & (CBAUD|CBAUDEX)) != B4000000 ) {

// On this line, you may insert a standard baud rate

} else {

ioctl(fd, MOXA_GET_SPECIAL_BAUD_RATE, &speed);

}

Non-Standard Baudrates and Baudrate Inaccuracy

Moxa’s drivers allow engineers to configure our serial devices for non-standard baudrates. Theoretically, these

devices may be set for any baudrate; however, in practice the only non-standard rates that will communicate

at the chosen baudrate are whole number factors of the base rate, 921,600 bps. For any non-standard rates

that are not a whole number factor of 921,600, there will be some inaccuracy in transmission speed relative to

the configured rate.

Standard baudrates are 50, 75, 110, 134, 150, 200, 300, 600, 1200, 1800, 2400, 4800, 9600, 19200, 38400,

57600, 115200, 230400, 460800, and 921600. Moxa’s drivers allow for any whole number factor of 921,600 to

be used without any performance loss (i.e., inaccuracy or deviation from the TBR) in the configured modulation

rate. To calculate the relative inaccuracy for non-standard baudrates that are not a whole number factor of

921,600, use the formula below:

Moxa TC-SW04-M12-4P-T [24/43] Tc sp04 db44 t configuring the baudrate

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