Lab04 - Serial port access

Use cat and picocom for serial line access.

cat allows to read data from a file or device. The Nucleo board will be present at /dev/ttyACM0. The default speed of the serial port set by the kernel driver is 115200 bd.

cat /dev/ttyACM0

The main issue with serial communication is the proper settings of the communication paramters such as:

• communication speed - baudrate
• number of bites - usually 8
• number of stop-bits - usually 1
• parity - in some applications none

Unix environment allows to control the serial line settings by stty command.

stty -F /dev/ttyS0 9600 cs8 -cstopb -parenb

Task:

• Set the proper parameters of the communication device by stty command
• Display the readings from the Nucleo board and demonstrate the Nucleo board returns different reply for different characters. When entering:
  • 'w' the board will reply by “Welcome to the Nucleo STM32F401RE” and when entering
  • 'a' the board will reply by your name
  • 'i' the board will reply by a random character

Perform the same task with picocom terminal (help man piccocom).

Use the application from HW01 and add functionality which opens the serial device and allows you to send and receive data from the board.

int hSerial = open( "/dev/ttyUSB0", O_RDWR| O_NONBLOCK | O_NDELAY );
// h = handle

struct termios o_tty;
// o = object
memset (&o_tty, 0, sizeof o_tty);
iRetVal = tcgetattr (hSerial , &o_tty);

unsigned char chArrCmd[] = {'*', 'I', 'D', 'N', '?', '\r', '\n', '\0'};
int n_written = write( hSerial, chArrCmd, sizeof(chArrCmd)-1 ); // why -1?

char chArrBuf [256];
memset (&chArrBuf , '\0', sizeof(chArrBuf) );

int n = read( hSerial, &chArrBuf , sizeof(chArrBuf) );

close(hSerial);

Recommended includes for this task are: stdio.h, stdlib.h, string.h, unistd.h, fcntl.h, errno.h, termios.h.