====== Lab04 - Serial port access ======

Use cat and picocom for serial line access.

==== cat ====
cat allows to read data from a file or device. The Nucleo board will be present at /dev/ttyACM0. The default speed of the [[https://en.wikipedia.org/wiki/Serial_port|serial port]] set by the kernel driver is 115200 bd. 
<code>
cat /dev/ttyACM0
</code>

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 [[http://www.computerhope.com/unix/ustty.htm|stty]] command.
<code>
stty -F /dev/ttyS0 9600 cs8 -cstopb -parenb
</code>

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

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

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

== Serial port open ==
<code>
int hSerial = open( "/dev/ttyUSB0", O_RDWR| O_NONBLOCK | O_NDELAY );
// h = handle
</code>
== Serial port settings ==
<code>
struct termios o_tty;
// o = object
memset (&o_tty, 0, sizeof o_tty);
iRetVal = tcgetattr (hSerial , &o_tty);
</code>
Now, modify the settings appropriately. The best guide for serial port programming in Unix is here:
[[https://support.dce.felk.cvut.cz/pos/cv5/doc/serial.html|serial port programming guide]].


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

== Serial port read ==
<code>
char chArrBuf [256];
memset (&chArrBuf , '\0', sizeof(chArrBuf) );

int n = read( hSerial, &chArrBuf , sizeof(chArrBuf) );
</code>

== Serial port close ==
<code>
close(hSerial);
</code>

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