stty gives control over the terminal settings.

To view the running settings, use:

stty -a

The syntax is:

stty <Signal> <Sequence>

• Signal is one of the predefined ones, see stty(1).
• Sequence maybe anything possible, but a good choice is defining an Escape Sequence (starting with ^).

Example:

 stty stop ^Y

NB: Regular sequences are interpreted case sensitive, escape sequences are not!

You typed C-s? Terminal hangs? In fact, you sent a stop signal.

Do not even try, typing reset does not help.

The output of stty -a gives some insight:

% stty -a
speed 38400 baud; rows 51; columns 89; line = 54;
intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = <undef>; eol2 = <undef>;
swtch = <undef>; start = ^Q; stop = ^S; susp = ^Z; rprnt = ^R; werase = ^W; lnext = ^V;
flush = ^O; min = 1; time = 0;
-parenb -parodd cs8 -hupcl -cstopb cread -clocal -crtscts
-ignbrk brkint ignpar -parmrk -inpck -istrip -inlcr -igncr icrnl ixon -ixoff -iuclc -ixany
imaxbel -iutf8
opost -olcuc -ocrnl onlcr -onocr -onlret -ofill -ofdel nl0 cr0 tab0 bs0 vt0 ff0
isig icanon iexten echo echoe echok -echonl -noflsh -xcase -tostop -echoprt echoctl echoke 

The values for stop and start are relevant here:

start = ^Q; 
stop = ^S;

Therefore, typing C-q should bring things back to normal.

stty can set the terminal's baud rate and it receives feedback whether the value was accepted. This may be used to find out what max baud rate a serial port supports. A simple script could loop over:

# stty -F /dev/ttyX <value>

checking the return value. With regular serial ports, max speed is typically 115200baud. USB-serial-adapters may do more, relevant with some OBD2-adapters for car diagnostics.

Standard baud values are found in /usr/include/asm-generic/termbits.h and /usr/include/asm-generic/termbits-common.h as defines with name B<value>:

#define     B0          0x00000000      /* hang up */
#define    B50          0x00000001
#define    B75          0x00000002
#define   B110          0x00000003
#define   B134          0x00000004
#define   B150          0x00000005
#define   B200          0x00000006
#define   B300          0x00000007
#define   B600          0x00000008      
#define  B1200          0x00000009
#define  B1800          0x0000000a
#define  B2400          0x0000000b
#define  B4800          0x0000000c
#define  B9600          0x0000000d
#define B19200          0x0000000e
#define B38400          0x0000000f

#define     B57600      0x00001001
#define    B115200      0x00001002
#define    B230400      0x00001003
#define    B460800      0x00001004
#define    B500000      0x00001005
#define    B576000      0x00001006
#define    B921600      0x00001007
#define   B1000000      0x00001008
#define   B1152000      0x00001009
#define   B1500000      0x0000100a
#define   B2000000      0x0000100b
#define   B2500000      0x0000100c
#define   B3000000      0x0000100d
#define   B3500000      0x0000100e
#define   B4000000      0x0000100f