Reading ints from serial port Arduino - c

Question

I've done a C program that writes an integer array into the Arduino:
// ...
FILE* file;
file = fopen("/dev/ttyuSB0","w");
for (int i = 0; i < 3; i++) {
fprintf(file, "%d ", rgb[i]);
}
fclose(file);
// ...
How can I do from my arduino code (.ino) to catch the three integers from the file?
while (Serial.available() > 0) {
// What can I do here ???
}

Answer 1

You need to read the data and put it into a buffer. After you encounter a ' ' character you terminate the string inside the buffer and convert it into an int.
When you do this three times you have read all three ints.
const uint8_t buff_len = 7; // buffer size
char buff[buff_len]; // buffer
uint8_t buff_i = 0; // buffer index
int arr[3] = {0,0,0}; // number array
uint8_t arr_i = 0; // number array index
void loop() {
while (Serial.available() > 0) {
char c = Serial.read();
if (buff_i < buff_len-1) { // check if buffer is full
if (c == ' ') { // check if got number terminator
buff[buff_i++] = 0; // terminate the string
buff_i = 0; // reset the buffer index
arr[arr_i++] = atoi(buff); // convert the string to int
if (arr_i == 3) { // if got all three numbers
arr_i = 0; // reset the number array index
// do something with the three integers
}
}
else if (c == '-' || ('0' <= c && c <= '9')) // if negative sign or valid digit
buff[buff_i++] = c; // put the char into the buffer
}
}
// maybe do some other stuff
}
Or if you don't mind blocking code[1] you can use builtin ParseInt.
void loop() {
while (Serial.available() > 0) {
arr[0] = Serial.parseInt();
arr[1] = Serial.parseInt();
arr[2] = Serial.parseInt();
Serial.read(); // read off the last space
// do something with the three integers
}
// maybe do some other stuff, but might be blocked by serial read
}
[1] If your computer has a hiccup and doesn't send all the data at once, your Arduino code will just wait for data and won't be doing anything else. Read more here.