Use Arduino signals as input for PC? - c++

Question

I recently got my hands on an Arduino (Uno), and I was wondering something.
I've got no external volume changer for my speakers, so I thought, maybe hook up a potentiometer to the Arduino, and then use that to control the volume (in Windows). But is that possible?
To read a value of an Arduino pin using maybe Visual C, C++ (or some more 'multi-platform' language)? And then using that to set the volume level in Windows (and if it's possible also in Linux).
I thought it might be possible, because if you use:
Serial.println(analogRead([pin with potentiometer]));
You can get the values of the potentiometer to the pc (via USB). So is there any way to read those values in C or C++?
I know how to set the volume in Windows via C or C++, I only need to know if there is a way to read out the values of a potentiometer in a (Visual) C or C++ script.

Answer 1

Definitely. And using exactly the same method: serial communication. Since I'm not a great Windows expert, I can't write you a complete Windows example, but here are some snippets that may get you started on a Unix (Linux, OS X, etc.):
Code on the Arduino:
#define POT_PIN 1
void setup()
{
Serial.begin(9600); // 9600 baud is more than enough
}
void loop()
{
int pot = analogRead(POT_PIN);
unsigned char byte = (pot + 2) >> 2; // round and divide by 4
Serial.write(pot);
delay(100); // or do something useful
}
Code on the computer:
#include <termios.h>
struct termios tio;
memset(&tio, 0, sizeof(tio));
// Open serial port in mode `8N1', non-blocking
tio.c_cflag = CS8 | CREAD | CLOCAL;
tio.c_cc[VMIN] = 1;
tio.c_cc[VTIME] = 5;
int fd = open(device, O_RDONLY);
cfsetospeed(&tio, B9600);
cfsetispeed(&tio, B9600);
tcsetattr(fd, TCSANOW, &tio);
while (1) {
unsigned char byte;
read(fd, &byte, 1);
use_some_library_to_set_volume(byte);
}

Answer 2

There are some things to consider.
You want the PC to listen to your "potentiometer Arduino" only. You don't want it to listen to any random USB data coming at any port. There is a need to create a data protocol which is somewhat unique to your device. If you just spam analog readings you'll get some raw data like "123 128 133 145", which could mean anything and come from any kind of device.
When you type Serial.whatever, the Arduino is likely spitting out an UART signal. I don't know a thing about Arduino, but hopefully it has either RS-232 or USB circuitry on board. You will need a matching port on the PC, the traditional RS-232 9 pin d-sub connector is getting increasingly rare on modern computers. You might need a RS-232 to USB converter.
You need a mean to determine which COM port the device is connected to. USB ports and traditional RS-232 ports work the same, as far as the PC is concerned. Either let the user pick the port manually, or design a more intelligent algorithm to find the port where your device is connected.
Study the Windows API for all the serial port routines. Documentation and examples at MSDN.