Fixing Communications between Arduino and C++ Mac OS X - c++

Question

I am having trouble communicating from C++ to Arduino using Serial. I have used the method discussed by Salil Kapur here: https://salilkapur.wordpress.com/2013/03/08/communicating-with-arduino-using-c/. I have adapted his strategy of writing directly to the Arduino's file using c++.For my specific task , I need to send a string of char’s (which are commands for the arduino to process) to the Arduino. I have already read the chars from a file in the C++ program, but for some reason, I am getting nothing from my Arduino Serial monitor when I send it over. I think that the baud rate might be the problem, but I am not positive. I will give you my code for specific help. If someone can advise me how to get the C++ to write the chars to the Serial monitor to be read:
C++:
#include
#include //For sleep()
#include //For FILE
#include //For ifstream
#include //For assert()
#include //For string
using namespace std;
int main()
{
//Setting up the output to the Arduino
FILE *arduino;
arduino = fopen(“/dev/tty.usbmodem1411″,”w”); //Declare the file in write mode
if (arduino == NULL) perror (“Error opening file”);
//Setting up the file input stream
ifstream inFile (“input.txt”);
assert(inFile.is_open());
char input = '\0'; //Starts out as NULL
while (input!= EOF) {
fprintf(arduino,”%c “, input); //Writing to the file
inFile >> input; //Getting the file input to make sure it isn’t the EOF
sleep(1);
}
fclose(arduino);
}
Arduino Code:
void setup()
{
Serial.begin(9600);
}
void loop()
{
char input;
if(Serial.available()) //If anything is in the Serial
{
input=Serial.read();
Serial.println(input); //Print out any input
}
}
Sample input from input.txt:
w a d s w d a a s d w
That string of characters will provide a direction (up, down, left, right) as per WASD.

Answer 1

It's possible to use the file handle to write data to a serial device, but it might be helpful to first try using the native Unix serial communication API as a sanity check.
Take a look at this post on todbot.com: Arduino-serial: C code to talk to Arduino
The todbot.com post describes a general purpose program for talking to an Arduino over its serial connection. The source has a lot of code for getting settings from the command line, and is a bit intimidating because it's robust, but the business end of the serial communication is fairly straightforward if you want to see how he does it.
I wrote my own series of posts on the topic, with some light-weight code (in parts 3 and 4) that demonstrates how to do almost exactly what you're trying to do.
How to read serial data from an Arduino in Linux with C: Part 1
I hope something in those links help! Serial communication is hard, so don't beat yourself up too much if it's not going your way.