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

Use cat and picocom for serial line access.

===== Communcation methods =====

==== cat - old method ====
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 parameters 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/ttyACM0 -brkint -icrnl -imaxbel -opost -onlcr -isig -icanon -iexten -echo -echoe -echoctl -echoke 115200
</code>

==== picocom ====
Perform the same task with picocom terminal (help man piccocom). 
Don't forget to set the proper baud rate (115200).

==== C app ====

== 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.


==== Lab Instructions ====
  * Download the files provided in link {{:courses:be5b99cpl:labs:lab04_x.zip|}}.
  * Compile and upload ''main.c'' file to NUCLEO board. Can you explain whats happening in ''main.c''?
  * Send and receive data to NUCLEO board by using the ''lab04_sender.cpp'' and ''lab04_receiver.cpp''. Can you explain what ''lab04_receiver.cpp'' and ''lab04_sender.cpp''codes are doing?
  * NOTICE 1: in every terminal that you want to run ''lab04_sender.cpp'' and ''lab04_receiver.cpp'', you need to run the command below to set up your serial communication.
<code>
stty -F /dev/ttyACM0 -brkint -icrnl -imaxbel -opost -onlcr -isig -icanon -iexten -echo -echoe -echoctl -echoke 115200
</code>
  * NOTICE 2: make sure that you only send and receive from one source. You wont recieve any data if you listen to NUCLEO with two terminals.
  * NOTICE 3: reset your board each time before running your code to make sure datas from previous running are not still in board buffer.
  * NOTICE 4: check that make file for nucleo board is written relative and it does not contain user name of any other person.

==== Lab Tasks ====
  * Change ''lab04_sender.cpp'' in a way that strings that are supposed to be sent are passed through the terminal.
  * Make board blink by sending ''led1'' and ''led0'' commands by ''lab04_sender.cpp'' from computer. You can make delays in cpp by 
<code>
#include<unistd.h>
unsigned int microsecond = 1000000;
usleep(3 * microsecond);//sleeps for 3 second
</code>
  * Modify ''main.c'' of NUCLEO board in a way that if an integer (1 digit) is sent to it, adds one and returns back through UART. If one is added to 9, it should return 0, not 10.
  * expand the exercise above for four digit numbers.